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Title: The Boy's Playbook of Science

Author: John Henry Pepper

Release date: January 13, 2013 [eBook #41839]
Most recently updated: October 23, 2024

Language: English

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*** START OF THE PROJECT GUTENBERG EBOOK THE BOY'S PLAYBOOK OF SCIENCE
***

THE BOY'S PLAYBOOK OF SCIENCE:
INCLUDING THE

Various Manipulations and Arrangements

OF
CHEMICAL AND PHILOSOPHICAL APPARATUS REQUIRED FOR THE SUCCESSFUL PERFORMANCE OF
SCIENTIFIC EXPERIMENTS.

IN ILLUSTRATION OF THE ELEMENTARY BRANCHES OF CHEMISTRY AND NATURAL PHILOSOPHY.

BY

JOHN HENRY PEPPER,
F.C.S., A. INST. C.E.; LATE PROFESSOR OF CHEMISTRY AT THE ROYAL POLYTECHNIC, ETC. ETC. AUTHOR OF
"THE PLAYBOOK OF METALS."

NEW EDITION.

Illustrated with 470 Engravings,
CHIEFLY EXECUTED FROM THE AUTHOR'S SKETCHES, BY H. G. HINE.

LONDON:

GEORGE ROUTLEDGE AND SONS,

THE BROADWAY, LUDGATE.

NEW YORK: 416, BROOME STREET.

1869.

LONDON.

SAVILL, EDWARDS AND CO., PRINTERS, CHANDOS STREET.
COVENT GARDEN.

Wheatstone's telephonic concert at the Polytechnic, in which the sounds and vibrations pass inaudible through an
intermediate hall, and are reproduced in the lecture-room unchanged in their qualities and intensities. Frontispiece.

TO
PROFESSOR LYON PLAYFAIR, C.B., F.R.S.
PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF EDINBURGH.

Dear Sir,
I Dedicate these pages to your Children, whom I often had the pleasure of seeing at the Polytechnic
during my direction of that Institution. I do so as a mark of respect and appreciation of your talent and
zeal, and of your public-spirited advocacy of the Claims of Science in this great and commercial
country.
Without making you responsible in any way for the shortcomings of this humble work on Elementary
Science, allow me to subscribe myself,
Dear Sir,
Yours most respectfully,

JOHN HENRY PEPPER.

CONTENTS.
PAGE
INTRODUCTION. 1
CHAPTER I.
THE PROPERTIES OF MATTER—IMPENETRABILITY 3
CHAPTER II.
CENTRIFUGAL FORCE 17
CHAPTER III.
THE SCIENCE OF ASTRONOMY 19
CHAPTER IV.
CENTRE OF GRAVITY 32
CHAPTER V.
SPECIFIC GRAVITY 48
CHAPTER VI.
ATTRACTION OF COHESION 59
CHAPTER VII.
ADHESIVE ATTRACTION 67
CHAPTER VIII.
CAPILLARY ATTRACTION 69
CHAPTER IX.
CRYSTALLIZATION 73
CHAPTER X.
CHEMISTRY 81
CHAPTER XI.
CHLORINE, IODINE, BROMINE, FLUORINE 129
CHAPTER XII.
CARBON, BORON, SILICON, SELENIUM, SULPHUR, PHOSPHORUS 151
CHAPTER XIII.
FRICTIONAL ELECTRICITY 173
CHAPTER XIV.
VOLTAIC ELECTRICITY 193
CHAPTER XV.
MAGNETISM AND ELECTRO-MAGNETISM 206
CHAPTER XVI.
ELECTRO-MAGNETIC MACHINES 211
CHAPTER XVII.
THE ELECTRIC TELEGRAPH 218
CHAPTER XVIII.
RUHMKORFF'S, HEARDER'S, AND BENTLEY'S COIL APPARATUS 230
CHAPTER XIX.
MAGNETO-ELECTRICITY 241

CHAPTER XX.
DIA-MAGNETISM 247
CHAPTER XXI.
LIGHT, OPTICS, AND OPTICAL INSTRUMENTS 255
CHAPTER XXII.
THE REFRACTION OF LIGHT 298
CHAPTER XXIII.
REFRACTING OPTICAL INSTRUMENTS 303
CHAPTER XXIV.
THE ABSORPTION OF LIGHT 327
CHAPTER XXV.
THE INFLECTION OR DIFFRACTION OF LIGHT 328
CHAPTER XXVI.
THE POLARIZATION OF LIGHT 335
CHAPTER XXVII.
HEAT 352
CHAPTER XXVIII.
THE STEAM-ENGINE 406
CHAPTER XXIX.
THE STEAM-ENGINE—continued 418

INTRODUCTION.
Although "The South Kensington Museum" now takes the lead, and surpasses all former scientific
institutions by its vastly superior collection of models and works of art, there will be doubtless many
thousand young people who may remember (it is hoped) with some pleasure the numerous popular
lectures, illustrated with an abundance of interesting and brilliant experiments, which have been
delivered within the walls of the Royal Polytechnic Institution during the last twenty years.
On many occasions the author has received from his young friends letters, containing all sorts of
inquiries respecting the mode of performing experiments, and it has frequently occurred that even
some years after a lecture had been discontinued, the youth, now become the young man, and anxious
to impart knowledge to some "home circle" or country scientific institution, would write a special
letter referring to a particular experiment, and wish to know how it was performed.
The following illustrated pages must be regarded as a series of philosophical experiments detailed in
such a manner that any young person may perform them with the greatest facility. The author has
endeavoured to arrange the manipulations in a methodical, simple, and popular form, and will indeed
be rewarded if these experiments should arouse dormant talent in any of the rising generation, and
lead them on gradually from the easy reading of the present "Boy's Book," to the study of the
complete and perfect philosophical works of Leopold Gmelin, Faraday, Brande, Graham, Turner, and
Fownes.
Every boy should ride "a hobby-horse" of some kind; and whilst play, and plenty of it, must be his
daily right in holiday time, he ought not to forget that the cultivation of some branch of the useful Arts
and Sciences will afford him a delightful and profitable recreation when satiated with mere play, or
imprisoned by bad weather, or gloomy with the unamused tediousness of a long winter's evening.
The author recollects with pleasure the half-holidays he used to devote to Chemistry, with some other
King's College lads, and in spite of terrible pecuniary losses in retorts, bottles, and jars, the most
delightful amusement was enjoyed by all who attended and assisted at these juvenile philosophical
meetings.
It has been well remarked by a clever author, that bees are geometricians. The cells are so constructed
as, with the least quantity of material, to have the largest sized spaces and the least possible interstices.
The mole is a meteorologist. The bird called the nine-killer is an arithmetician, also the crow, the wild
turkey, and some other birds. The torpedo, the ray, and the electric eel are electricians. The nautilus is
a navigator. He raises and lowers his sails, casts and weighs anchor, and performs nautical feats.
Whole tribes of birds are musicians. The beaver is an architect, builder, and wood-cutter. He cuts
down trees and erects houses and dams. The marmot is a civil engineer. He does not only build
houses, but constructs aqueducts, and drains to keep them dry. The ant maintains a regular standing
army. Wasps are paper manufacturers. Caterpillars are silk-spinners. The squirrel is a ferryman. With
a chip or a piece of bark for a boat, and his tail for a sail, he crosses a stream. Dogs, wolves, jackals,
and many others, are hunters. The black bear and heron are fishermen. The ants are day-labourers.
The monkey is a rope dancer. Shall it, then, be said that any boy possessing the Godlike attributes of
Mind and Thought with Freewill can only eat, drink, sleep, and play, and is therefore lower in the
scale of usefulness than these poor birds, beasts, fishes, and insects? No! no! Let "Young England"
enjoy his manly sports and pastimes, but let him not forget the mental race he has to run with the
educated of his own and of other nations; let him nourish the desire for the acquisition of "scientific

knowledge," not as a mere school lesson, but as a treasure, a useful ally which may some day help him
in a greater or lesser degree to fight "The Battle of Life."

THE

BOY'S PLAYBOOK OF SCIENCE.

CHAPTER I.
THE PROPERTIES OF MATTER—IMPENETRABILITY.

In the present state of our knowledge it seems to be universally agreed, that we cannot properly
commence even popular discussions on astronomy, mechanics, and chemistry, or on the
imponderables, heat, light, electricity, and magnetism, without a definition of the general term
"matter;" which is an expression applied by philosophers to every species of substance capable of
occupying space, and, therefore, to everything which can be seen and felt.
The sun, the moon, the earth, and other planets, rocks, earths, metals, glass, wool, oils, water, alcohol,
air, steam, and hosts of things, both great and small, all solids, liquids and gases, are included under
the comprehensive term matter. Such a numerous and varied collection of bodies must necessarily
have certain qualities, peculiarities, or properties; and hence we come in the first place to consider
"The general powers or properties of matter." Thus, if we place a block of wood or stone in any
position, we cannot take another substance and put it in the space filled by the wood or stone, until the
latter be removed. Now this is one of the first and most simple of the properties of matter, and is called
impenetrability, being the property possessed by all solid, liquid, and gaseous bodies, of filling a space
to the exclusion of others until they be removed, and it admits of many amusing illustrations, both as
regards the proof and modification of the property.
Thus, a block of wood fills a certain space: how is it (if impenetrable) that we can drive a nail into it?
A few experiments will enable us to answer this question.
Into a glass (as depicted at fig. 1) filled with spirits of wine, a quantity of cotton wool many times the
bulk of the alcohol may (if the experiment is carefully performed) be pushed without causing a drop to
overflow the sides of the vessel.

Fig. 1.
Here we seem to have a direct contradiction of the simple and indisputable truth, that "two things
cannot occupy the same space at once." But let us proceed with our experiments:—
We have now a flask full of water, and taking some very finely-powdered sugar, it is easy to introduce
a notable quantity of that substance without increasing the bulk of the water; the only precaution
necessary, is not to allow the sugar to fall into the flask in a mass, but to drop it in grain by grain, and
very slowly, allowing time for the air-bubbles (which will cling to the particles of sugar) to pass off,

and for the sugar to dissolve. Matter, in the experiments adduced, appears to be penetrable, and the
property of impenetrability seems only to be a creation of fancy: reason, however, enables us to say
that the latter is not the case.

Fig. 2.
A nail may certainly be hammered into wood, but the particles are thrust aside to allow it to enter.
Cotton wool may be placed in spirits of wine because it is simply greatly extended and bulky matter,
which, if compressed, might only occupy the space of the kernel of a nut, and if this were dropped into
a half-pint measure full of alcohol, the increase of bulk would not cause the spirit to overflow. The
cotton-wool experiment is therefore no contradiction of impenetrability. The experiment with the
sugar is the most troublesome opponent to our term, and obliges us to amend and qualify the original
definition, and say, that the ultimate or smallest particles or atoms of bodies only are impenetrable;
and we may believe they are not in close contact with each other, because certain bulks of sugar and
water occupy more space separately than when mixed.

Fig. 3.

If we compare the flask of water to a flask full of marbles, and the sugar to some rape-seed, it will be
evident that we may almost pour another flask full of the latter amongst the marbles, because they are
not in close contact with each other, but have spaces between them; and after pouring in the rape-seed,
we might still find room for some fine sand.
The particles of one body may thus enter into the spaces left between those of another without
increasing its volume; and hence, as has been before stated, "The atoms only of bodies are truly
impenetrable."
This spreading, as it were, of matter through matter assumes a very important function when we come
to examine the constitution of the air we breathe, which is chiefly a mechanical mixture of gases:
seventy-nine parts by volume or measure of nitrogen gas, twenty-one parts of oxygen gas, and four
parts of carbonic acid vapour in every ten thousand parts of air having the following relations as to
weight:—

Specific
gravity.
Nitrogen 972
Oxygen 1105
Carbonic acid 1524

It might be expected that these gases would arrange themselves in our atmosphere in the above order,
and if that were the case, we should have the carbonic-acid gas (a most poisonous one) at the bottom,
and touching the earth, then the oxygen, and, last of all, the nitrogen; a state of things in which
organized life could not exist. The gases do not, however, separate: indeed, they seem to act as it were
like vacuums to one another, and "the diffusion of gases" has become a recognised fact, governed by
fixed laws. This fact is curiously illustrated, as shown in our cut, by filling a bottle with carbonic acid,
and another with hydrogen; and having previously fitted corks to the bottles, perforated so as to admit
a tube, place the bottle containing the carbonic acid on the table, then take the other full of hydrogen,
keeping the mouth downwards, and fit in the cork and tube: place this finally into the cork of the
carbonic-acid bottle, which may be a little larger than the other, in order to make the arrangement
stand firmer; and after leaving them for an hour or so, the carbonic acid, which is twenty-two times
heavier than the hydrogen, will ascend to the latter, whilst the hydrogen will descend to the carbonic
acid. The presence of the carbonic acid in the hydrogen bottle is easily proved by pouring in a wine-
glassful of clear lime-water, which speedily becomes milky, owing to the production of carbonate of
lime; whilst the proof of the hydrogen being present in the carbonic acid is established by absorbing
the latter with a little cream of lime—i.e., slacked lime mixed to the consistence of cream with some
water—and setting fire to the hydrogen that remains, which burns quietly with a yellowish flame if
unmixed with air; but if air be admitted to the bottle, the mixture of air and hydrogen inflames rapidly,
and with some noise.

Fig. 4.
One of the most elegant modes of showing the diffusion of gases is by taking a large round dry porous
cell, such as would be employed in a voltaic battery, and having cemented a brass cap with a glass
tube attached to its open extremity, it may then be supported by a small tripod of iron wire, and the
end of the glass tube placed in a tumbler containing a small quantity of water coloured blue with
sulphate of indigo. If a tolerably large jar containing hydrogen is now placed over the porous cell,
bubbles of gas make their escape at the end of the tube, because the hydrogen diffuses itself more
rapidly into the porous cell than the air which it already contains passes out. When the jar is removed,
the reverse occurs, hydrogen diffuses out of the porous cell, and the blue liquid rises in the tube.
This diffusive force prevents the accumulation of the various noxious gases on the earth, and spreads
them rapidly through the great bulk of the atmosphere surrounding the globe.

Fig. 5.
a. The porous cell. b. The jar of hydrogen. c. The brass cap and glass tube d, the end of which dips into the tumbler
containing the solution of indigo e. f f. The wire and stand supporting the porous cell and tube in tumbler.

Although air and other gases are invisible, they possess the property of impenetrability, as may be
easily proved by various experiments. Having opened a pair of common bellows, stop up the nozzle
securely, and it is then impossible to shut them; or, fill a bladder with air by blowing into it, and tie a
string fast round the neck; you then find that you cannot, without breaking the bladder, press the sides
together.
It is customary to say that a vessel is empty when we have poured out the water which it contained.
Having provided two glass vessels full of water, place each of them in an empty white pan, to receive
the overflow, then lay an orange upon the surface of the water of one of them, and being provided with
a cylindrical glass, open at one end, with a hole in the centre of the closed end, place your finger
firmly over the orifice, and endeavour, by inverting the glass over the orange, and pressing upon the
surface of the water, to make it enter the interior of the glass cylinder; the resistance of the air will
now cause the water to overflow into the white pan, whilst the orange will not enter. The orange may
now be transferred to the other vessel of water, and on removing the finger from the orifice of the
cylindrical glass, and inverting it as before over the orange, the air will rush out and the orange and
water will enter, whilst there will be no overflow as in the preceding experiment. The comparison of
the two is very striking, and at once teaches the fact desired.

Fig. 6 represents the water overflowing, as the Fig. 7. The orange has entered the glass vessel,
glass, with the orifice closed, is pressed down, and the air having passed from the orifice, no
proving the impenetrability of air. water overflows.

Whilst the vessels of water are still in use, another pretty experiment may be made with the metal
potassium. First throw a small piece of the metal on the surface of the water, to show that it takes fire
on contact with that fluid; then, having provided a gas-jar, fitted with a cap and stop-cock, and a little
spoon screwed into the bottom of the stop-cock inside the gas-jar, place another piece of potassium in
the little spoon, and, after closing the stop-cock, push the jar into one of the vessels of water: as
before, the impenetrability of the air prevents the water flowing up to the potassium; but, on opening
the stop-cock, the air escapes, the water rushes up, and directly it touches the potassium, combustion
ensues.

Fig. 9. Gas-jar; stop-cock open; the air passes,
Fig. 8. Gas-jar with stop-cock closed, and potassium
the water enters, and the potassium is
in ladle; air prevents the entrance of the water.
inflamed.

Having sufficiently indicated the nature and meaning of impenetrability, we may proceed to discuss
experimentally three other marked and special qualities of matter—viz., inertia, gravity, and weight.

INERTIA, OR PASSIVENESS.

Inertia is a power which (according to Sir Isaac Newton) is implanted in all matter of resisting any
change from a state of rest. It is sometimes called vis inertiæ, and is that property possessed by all
matter, of remaining at rest till set in motion, and vice versâ; and it expresses, in brief terms, resistance
to motion or rest.
A pendulum clock wound up and ready to go, does not commence its movements, until the inertia of
the pendulum is overcome, and motion imparted to it. On the other hand, when seated in a carriage,
should any obstruction cause the horse to stop suddenly, it is only perhaps by a violent effort, if at all,
that we can resist the onward movement of our bodies. To illustrate inertia, construct a metal tray,
about three feet long, two feet wide, and two inches deep, with a glass bottom, and arrange it on a
framework supported by legs, like a table, and having filled it with water, let the room be darkened,
and then place under the tank a lighted candle, at a sufficient distance from the glass to prevent the
heat cracking it. If a piece of calico or paper, stretched on a framework, be now held over the water at

an angle of about thirty degrees, all that occurs on the surface of the water will be rendered visible on
such screen. Attention may now be directed to the quiescence, or the inertia of the water, while the
opposite condition of movement and formation of the waves may be beautifully shown by touching
the surface of the water with the finger; the miniature waves being depicted on the screen, and
continuing their motion till set at rest by striking against the sides of the tin tray.

Fig. 10.
Tin tray, with glass bottom, full of water; candle placed underneath.

Fig. 11.
Fig. 11. Same tray, with calico screen; showing the waves as they are produced by touching the surface of the water
with the finger.

Should the above experiment be thought too troublesome or expensive to prepare, inertia may be
demonstrated by filling a tea-cup or other convenient vessel with water, and after moving rapidly with
it in any direction, if we stop suddenly, the rigidity of all parts of the cup we hold brings them
simultaneously to a state of rest; but the mobility of the liquid particles allows of their continuing in
motion in their original direction, and the liquid is spilled. Thus, carelessness in handing and spilling a
cup of tea (though not to be recommended) serves to illustrate an important principle. The inertia of
bodies in motion is further and lamentably illustrated by the accidents caused from the sudden
stoppage of a railway train whilst in rapid motion, when heads and knees come in contact with
frightful results.—It is more especially demonstrated by the earth, the moon, and the other planets
continuing their motion for ever in the absence of any friction or resistance to oppose their onward
progress. It is the friction arising from the roughness of the ground, the resistance of the air, and the
force of the earth's attraction, which puts a stop to bodies set in motion about the surface of the earth.

GRAVITATION.

Inertia represents a passive force, gravitation, an active condition of matter; and this latter may truly
be termed a force of attraction, because it acts between masses at sensible or insensible distances: it is
illustrated by a stone, unsupported, falling to the ground; by the stone pressing with force on the earth,
and requiring power to raise it from the ground: indeed, it is commonly reported that it was by an
accident—"an apple falling from a tree"—that the great Newton was led to reflect on the universal law
of gravitation, and to pronounce upon it in the following memorable words:—

"Every particle of matter in the universe attracts every other particle of matter with a force or power
directly proportional to the quantity of matter in each, and decreasing as the squares of the distances
which separate the particles increase."
These words may appear very obscure to our juvenile readers; but when dissected and examined
properly, they clearly define the property of gravitation. For instance, "every particle attracts every
other with a force proportional to the quantity of matter in each." This statement was verified some
years back by Maskelyne, who, having sought out and discovered a steep, precipitous rock in the
Schichallion mountains, in Scotland, suspended from it a metal weight by a cord, and going to a
convenient distance with a telescope, and observing the weight, he found that it did not hang
perpendicularly, like an ordinary plumb line, but was attracted, or impelled, to the sides of the rock by
some kind of attraction, which, of course, could be no other than that indicated by Newton as the
attraction of gravitation.

Fig. 12.
The Schichallion Rocks. The dotted line and weight a represent the ordinary position of a plumb line, whilst the line
of the weight b indicates (of course, with some exaggeration) the attractive power of the mass of the rock drawing it
from the perpendicular.

This truly wonderful power of attraction pervades all masses; and being, as before stated, proportional
to the quantity of matter, if a man could be transported to the surface of the sun, he would become
about thirty times heavier: he would be attracted, or impelled, to the sun with thirty times more
gravitating force than on the surface of the earth, and would weigh about two tons. Of course, nursing
a baby on the sun's surface would be a very serious affair with our ordinary strength; whilst on some
of the smaller planets, such as Ceres and Pallas, we should probably gravitate with a force of a few

pounds only, and with the same muscular power now possessed, we should quite emulate the exploits
of those domestic little creatures sometimes called "the industrious fleas," and our jumping would be
something marvellous.
There is no very good lecture-table experiment that will illustrate gravitation, although attention may
be directed to the fact of a piece of potassium thrown on the surface of water in a plate generally
rushing to the sides, and, as if attracted, attaching itself with great force to the substance of the pottery
or porcelain; or, if a model ship, or lump of wood, be allowed to float at rest in a large tank of water,
and a number of light chips of wood or bits of straw be thrown in, they generally collect and remain
around the larger floating mass.
A very good idea, however, may be afforded of the universal action of gravity maintaining all things in
their natural position on the earth by taking a hoop and arranging in and upon it balls, or a model ship,
or other toy, and wires, as depicted in our diagram.

Fig. 13.
a. The centre ball, representing the earth's centre of gravity. w w w w. Four wires fixed into centre ball, and passing
through and secured in the hoop, projecting about one foot from the circumference. b b b b. Two balls—a model
ship and toy—working on the wires like beads, with vulcanized India-rubber straps attached to them and the
circumference of the hoop.

With this simple apparatus we may illustrate the upward, downward, and sideway movement of bodies
from the earth, and the counteraction by the force of gravitation of any tendency of matter to fall away
from the globe, which is represented in the model by the india-rubber springs pulling the balls and
toys back again to the circumference of the hoop.
The attraction of gravitation decreases (quoting the remainder of Newton's definition) as the squares
of the distances which separate the particles increase—i.e., it obeys the principle called "inverse
proportion"—viz., the greater the distance, the less gravitating power; the less the distance, the greater
the power of gravitation. Gravitation is like the distribution of light and other radiant forces, and may
be thus illustrated.

Fig. 14.
Place a lighted candle, marked a, at a certain distance from No. 1, a board one foot square; at double the distance
the latter will shadow another board, No. 2, four feet square; at three times, No. 3, nine feet square; at four, No. 4,
sixteen feet; and so on.

To make the comparison between the propagation of light and the attraction of gravitation, we have
only to imagine the candle, a, to represent the point where the force of gravity exists in the highest
degree of intensity; suppose it to be the sun—the great centre of this power in our planetary system. A
body, as at No. 1, at any given distance will be attracted (like iron-filings to a magnet) with a certain
force; at twice the distance, the square of two being four, and by inverse proportion, the attraction will
be four times less; at thrice the distance, nine times less; at the fourth distance, sixteen times less; and
so on. With the assistance of this law, we may calculate, roughly, the depth of a well, or a precipice, or
a column, by ascertaining the time occupied in the fall of a stone or other heavy substance. A falling
body descends about 16 feet in one second, 64 feet in two seconds, 144 feet in three seconds, 256 feet
in four seconds, 400 feet in five seconds, 576 feet in six seconds; the spaces passed over being as the
squares of the times.
Suppose a stone takes three seconds in falling to the surface of the water in a well, then 3 × 3 = 9 × 16
= 144 feet would be a rough estimate of the depth. The calculation will exceed the truth in
consequence of the stone being retarded in its passage by the resistance of the air.
All bodies gravitate equally to the earth: for instance, if an open box, say one foot in length, two
inches broad, and two inches deep, be provided with a nicely-fitted bottom, attached by a hinge, a
number of substances, such as wood, cork, marble, iron, lead, copper, may be arranged in a row; and
directly the hand is withdrawn, the moveable flap flies open, and if the manipulation with the
disengagement of the trap-door is good, the whole of the substances are seen to proceed to the earth in
a straight line, as shown in our drawing.

Fig. 15.

Fig. 16.
If a heavy substance, like gold, be greatly extended by hammering and beating into thin leaves, and
then dropped from the hand, the resistance of the air becomes very apparent; and a gold coin and a
piece of gold-leaf would not reach the earth at the same time if allowed to fall from any given height.
This fact is easily displayed by the assistance of a long glass cylindrical vessel placed on the air-pump,
with suitable apparatus arranged with little stages to carry the different substances; upon two of them
may be placed a feather and a gold coin, and on the third, another gold coin and a piece of gold-leaf.
In arranging the experiment, great care ought to be taken that the little stages are all nicely cleaned,
and free from any oil, grease, or other matter which might cause the feathers or the gold-leaf to cling
to the stages when they are disengaged, by moving the brass stop round that works in the collar of
leathers. Sometimes these leathers are oiled, and in that case, when the vacuum is made, the oil, by the
pressure, is squeezed out, and, passing down, may reach the stages and spoil the experiment, by
causing the feathers and gold-leaf to stick to the brass, producing great disappointment, as the
illustration, usually called the "guinea and feather glass experiment" takes some time to prepare. The
air-pump being in good order, the long glass is first greased on the lower welt or edge, and then placed
firmly on the air-pump plate. The top edge, or welt, may now be greased, and the gold coins, feathers,
and gold-leaf arranged in the drop-apparatus; this is carefully placed on the top of the glass, and firmly
squeezed down. The author has always found a tallow candle, rolled in a sheet of paper (so as to leave
about half the candle exposed), the best grease to smear the glass with for air-pump experiments; if the
weather is cold, the candle may be placed for a few minutes before an ordinary fire to soften the

tallow. Pomatum answers perfectly well when the surfaces of glass and
brass are all nicely ground; but as air-pumps and glasses by use get
scratched and rubbed, the tallow seems to fill up better all ordinary
channels by which air may enter to spoil a vacuum.
The apparatus being now arranged, the air is pumped
out; and here, again, care must be taken not to shake
the gold off the stages. When a proper vacuum has
been obtained, which will be shown by the pump-
gauge, the stop is withdrawn from one of the stages,
and the gold and feather are seen to fall
simultaneously to the air-pump plate. Another stage,
with the gold-leaf and coin, may now be detached;
both showing distinctly, that when the resistance of
the air is withdrawn, all bodies, whether called light
or heavy, gravitate equally to the earth. Then, the
screw at the bottom of the pump barrels being
opened, attention may be directed to the whizzing
noise the air makes on entering the vacuum, and
when the air is once more restored to the long glass
vessel, the last stage may be allowed to fall; and now,
the gold coin reaches the pump-plate first, and the
feather, lingering behind, loses (as it were) the race,
and touches the plate after the gold coin; thus
demonstrating clearly the resistance of the air to
falling bodies.
Fig. 17.
Another, and perhaps less troublesome, mode of
showing the same fact, is to use a long glass tube closed at each end with brass
caps cemented on. One cap should have the largest possible aperture closed by a
brass screw, and the other may fit a small hand-pump.

Fig. 18.

Fig. 19.
a b. Glass tube containing a piece of gold and a feather, which are placed in at the large aperture a. c. Small hand-
pump.

If a piece of gold and a small feather are placed in the tube, it may be shown that the former reaches
the bottom of the tube first, whilst it is full of air, and when the air is withdrawn by means of the
pump, and the tube again inverted, both the gold and the feather fall in the same time.

For this reason, all attempts to measure heights or depths by observing the time occupied by a falling
body in reaching the earth must be incorrect, and can only be rough approximations. An experiment
tried at St. Paul's Cathedral, with a stone, which was allowed to fall from the cupola, indicated the
time occupied in the descent to be four and a half seconds: now, if we square this time, and multiply
by 16, a height of 324 feet is denoted; whereas the actual height is only 272 feet, and the difference of
52 feet shows how the stone was retarded in its passage through the air; for, had there been no
obstacle, it would have reached the ground in 4-3/20ths seconds.
The force of gravitation is further demonstrated by the action of the sun
and moon raising the waters of the ocean, and producing the tides; and also
by the earth and moon, and other planets and satellites, being prevented
from flying from their natural paths or orbits around the sun. It is also very
clearly proved that there must be some kind of attractive force resident in
the earth, or else all moveable things, the water, the air, the living and dead
matters, would fly away from the surface of the earth in obedience to what
is called "centrifugal force." Our earth is twenty-four hours in performing
one rotation on its axis, which is an imaginary line drawn from pole to
pole, and represented by the wire round which we cause a sphere to rotate.
All objects, therefore, on the earth are moving with the planet at an
enormous velocity; and this movement is called the earth's diurnal, or daily
rotation. Now, it will be remembered, that mud or other fluid matter flies
off, and is not retained by the circumference of a wheel in motion: when a
mop is trundled, or a dog or sheep, after exposure to rain, shake
themselves, the water is thrown off by what is called centrifugal force
(centrum, a centre, fugio, to fly from).

Fig. 20.

CHAPTER II.
CENTRIFUGAL FORCE.

That power which drives a revolving body from a centre, and it may be illustrated by turning a closed
parasol, or umbrella, rapidly round on its centre, the stick being the axis—the ribs fly out, and if there
is much friction in the parts, the illustration is more certain by attaching a bullet to the end of each rib,
as shown in our drawing.

Fig. 21.
The same fact may be illustrated by a square mahogany rod, say one inch square and three feet long,
with two flaps eighteen inches in length, hanging by hinges, and parallel to the sides of the centre rod,
which immediately fly out on the rotation of the long centre piece.

Fig. 22.
The toy called the centrifugal railway is also a very pretty illustration of the same fact. A glass of
water, or a coin, may be placed in the little carriage, and although it must be twice hanging
perpendicular in a line with the earth, the carriage does not tumble away from its appointed track, and
the centrifugal force binds it firmly to the interior of the circle round which it revolves.

Fig. 23.
Another striking and very simple illustration is to suspend a hemispherical cup by three cords, and
having twisted them, by turning round the cup, it may be filled with water, and directly the hand is
withdrawn, the torsion of the cord causes the cup to rotate, and the water describes a circle on the
floor, flying off at a tangent from the cup, as may be noticed in the accompanying cut.

Fig. 24.
A hoop when trundled would tumble on its side if the force of gravitation was not overcome by the
centrifugal force which imparts to it a motion in the direction of a tangent (tango, to touch) to a circle.
The same principle applies to the spinning-top—this toy cannot be made to stand upon its point until
set in rapid motion.
Returning again to the subject of gravitation, we may now consider it in relation to other and more
magnificent examples which we discover by studying the science of astronomy.

CHAPTER III.
THE SCIENCE OF ASTRONOMY.

In a work of this kind, professedly devoted to a very brief and popular view of the different scientific
subjects, much cannot be said on any special branch of science; it will be better, therefore, to take up
one subject in astronomy, and by discussing it in a simple manner, our young friends may be
stimulated to learn more of those glorious truths which are to be found in the published works of many
eminent astronomers, and especially in that of Mr. Hind, called "The Illustrated London Astronomy."
One of the most interesting subjects is the phenomenon of the eclipse of the sun; and as 1858 is likely
to be long remembered for its "annular eclipse," we shall devote some pages and illustrations to this
subject.
Eclipses of the sun are of three kinds—partial, annular, and total. Many persons have probably seen
large partial eclipses of the sun, and may possibly suppose that a total eclipse is merely an intensified
form of a partial one; but astronomers assert that no degree of partial eclipse, even when the very
smallest portion of the sun remains visible, gives the slightest idea of a total one, either in the
solemnity and overpowering influence of the spectacle, or the curious appearances which accompany
it.
The late Mr. Baily said of an eclipse (usually called that of Thales), which caused the suspension of a
battle between the Lydians and Medes, that only a total eclipse could have produced the effect
ascribed to it. Even educated astronomers, when viewing with the naked eye the sun nearly obscured
by the moon in an annular eclipse, could not tell that any part of the sun was hidden, and this was
remarkably verified in the annular eclipse of the 15th March of this year.
During the continuance of a total eclipse of the sun, we are permitted a hasty glance at some of those
secrets of Nature which are not revealed at any other time—glories that hold in tremulous amazement
even veteran explorers of the heavens and its starry worlds.
The general meaning of an eclipse may be shown very nicely by lighting a common oil, or oxy-
hydrogen lantern in a darkened room, and throwing the rays which proceed from it on a three-feet
globe. The lantern may be called the sun, and, of course, it is understood that correct comparative
sizes are not attempted in this arrangement; if it were so, the globe representing the earth would have
to be a mere speck, for if we make the model of the sun in proportion to a three-feet globe, no ordinary
lecture hall would contain it. This being premised, attention is directed to the lantern, which, like the
sun, is self-luminous, and is giving out its own rays; these fall upon the globe we have designated the
earth, and illuminate one-half, whilst the other is shrouded in darkness, reminding us of the opacity of
the earth, and teaching, in a familiar manner, the causes of day and night. Another globe, say six
inches in diameter, and supported by a string, may be compared to the moon, and, like the earth, is
now luminous, and shines only by borrowed light: the moon is simply a reflector of light; like a sheet
of white cardboard, or a metallic mirror. When, therefore, the small globe is passed between the
lantern and the large globe, a shadow is cast on the large globe: it is also seen that only the half of the
small globe turned towards the lantern is illuminated, while the other half, opposite the large globe, is
in shadow or darkness. And here we understand why the moon appears to be black while passing
before the sun; so also by moving the small globe about in various curves, it is shown why eclipses are
only visible at certain parts of the earth's surface; and as it would take (roughly speaking) fifty globes
as large as the moon to make one equal in size to our earth, the shadow it casts must necessarily be

small, and cannot obscure the whole hemisphere of the earth turned towards it. An eclipse of the sun
is, therefore, caused by the opaque mass of moon passing between the sun and the earth. Whilst an
eclipse of the moon is caused by the earth moving directly between the sun and the moon: the large
shadow cast by the earth renders a total eclipse of the moon visible to a greater number of spectators
on that half of the earth turned towards the moon. All these facts can be clearly demonstrated with the
arrangement already described, of which we give the following pictorial illustration:—

Fig. 25.
In using this apparatus, it should be explained that if the moon were as large as the sun, the shadow
would be cylindrical like the figure 1, and of an unlimited length. If she were of greater magnitude, it
would precisely resemble the shadow cast in the experiment already adduced with the lantern and
shown at No. 2. But being so very much smaller than the sun, the moon projects a shadow which
converges to a point as shown in the third diagram.

Fig. 26.

Fig. 27.

Fig. 28.
In order to comprehend the difference between an annular and a total eclipse of the sun, it is necessary
to mention the apparent sizes of the sun and moon: thus, the former is a very large body—viz., eight
hundred and eighty-seven thousand miles in diameter; but then, the sun is a very long way off from
the earth, and is ninety millions of miles distant from us; therefore, he does not appear to be very
large: indeed, the sun seems to be about the same size as the moon; for, although the sun's diameter is
(roughly speaking) four hundred times greater than that of the moon, he is four hundred times further
away from us, and, consequently, the sun and moon appear to be the same size, and when they come
in a straight line with the eye, the nearer and smaller body, the moon, covers the larger and more
distant mass, the sun; and hence, we have either an annular, or a total eclipse, showing how a small
body may come between the eye and a larger body, and either partially or completely obscure it.
With respect to an annular eclipse, it must be remembered, that the paths of all bodies revolving round
others are elliptical; i.e., they take place in the form of an ellipse, which is a figure easily
demonstrated; and is, in fact, one of the conic sections.
If a slice be taken off a cone, parallel with the base, we have a circle thus—

Fig. 29.
If it be cut obliquely, or slanting, we see at once the figure spoken of, and have the ellipse as shown in
this picture.

Fig. 30.
Now, the ellipse has two points within it, called "the foci," and these are easily indicated by drawing
an ellipse on a diagram-board, in which two nails have been placed in a straight line, and about twelve
inches apart. Having tied a string so as to make a loop, or endless cord, a circle may first be drawn by
putting the cord round one of the nails, and holding a piece of chalk in the loop of the string, it may be
extended to its full distance, and a circle described; here a figure is produced round one point, and to
show the difference between a circle and an ellipse, the endless cord is now placed on the two nails,
and the chalk being carried round inside the string, no longer produces the circle, but that familiar
form called the oval. As a gardener would say, an oval has been struck; and the two points round
which it has been described, are called the foci. This explanation enables us to understand the next
diagram, showing the motion of the earth round the sun; the latter being placed in one of the foci of a
very moderate ellipse, and the various points of the earth's orbit designated by the little round globes
marked a, b, c, d, where it is evident that the earth is nearer to the sun at b than at d. In this diagram
the ellipse is exaggerated, as it ought, in fact, to be very nearly a circle.

Fig. 32.
Fig. 31.

We are about three millions of miles nearer to the sun in the winter than we are in the summer; but
from the more oblique or slanting direction of the rays of the sun during the winter season, we do not
derive any increased heat from the greater proximity. The sun, therefore, apparently varies in size; but
this seeming difference is so trifling that it is of no importance in the discussion: and here we may ask,
why does the earth move round the sun? Because it is impelled by two forces, one of which has
already been fully explained, and is called the centrifugal power, and the other, although termed the
centripetal force, is only another name for the "attraction of gravitation."

Fig. 33.
To show their mutual relations, let us suppose that, at the creation of the universe, the earth, marked a,
was hurled from the hand of its Maker; according to the law of inertia, it would continue in a straight
line, a c, for ever through space, provided it met with no resistance or obstruction. Let us now suppose
the earth to have arrived at the point b, and to come within the sphere of the attraction of the sun s;
here we have at once contending forces acting at right angles to each other; either the earth must
continue in its original direction, a c, or fall gradually to the sun. But, mark the beauty and harmony of
the arrangement: like a billiard-ball, struck with equal force at two points at right angles to each other,
it takes the mean between the two, or what is termed the diagonal of the parallelogram (as shown in
our drawing of a billiard-table), and passes in the direction of the curved line, b d; having reached d, it
is again ready to fly off at a tangent; the centrifugal force would carry it to e, but again the gravitating
force controls the centripetal, and the earth pursues its elliptical path, or orbit, till the Almighty Author
who bade it move shall please to reverse the command.

Fig. 34.

The mutual relations of the centripetal and centrifugal forces may be
illustrated by suspending a tin cylindrical vessel by two strings, and having
filled it with water, the vessel may be swung round without spilling a
single drop; of course, the movement must be commenced carefully, by
making it oscillate like a pendulum.
The cord which binds it to the finger may be
compared to the centripetal force, whilst the
centrifugal power is illustrated by the water
pressing against the sides and remaining in the
vessel. Upon the like principles the moon
revolves about the earth, but her orbit is more
elliptical than that of the earth around the sun;
and it is evident from our diagram that the
moon is much further from the earth at a than
at b. As a natural consequence, the moon
Fig. 36. appears sometimes a little larger and
Fig. 35.
sometimes smaller than the sun; the apparent
mean diameter of the latter being thirty-two
minutes, whilst the moon's apparent diameter varies from twenty-nine and a half to thirty-three and a
half minutes. Now, if the moon passes exactly between us and the sun when she is apparently largest,
then a total eclipse takes place; whereas, if she glides between the sun and ourselves when smallest—
i.e., when furthest off from the earth—then she is not sufficiently large to cover the sun entirely, but a
ring of sunlight remains visible around her, and what is called an annular eclipse of the sun occurs.
This fact may be shown in an effective manner by placing the oxy-hydrogen lantern before a sheet, or
other white surface, and throwing a bright circle of light upon it, which may be called the sun; then, if
a round disc of wood be passed between the lantern and the sheet, at a certain distance from the nozzle
of the lantern, all the light is cut off, the circle of light is no longer apparent, and we have a
resemblance to a total eclipse.

Fig. 37.
By taking the round disc of wood further from the lantern, and repeating the experiment, it will be
found that the whole circle of light is not obscured, but a ring of light appears around the dark centre,
corresponding with the phenomenon called the annular (ring-shaped) eclipse.
If a bullet be placed very near to one eye whilst the other remains closed, a large target may be wholly
shut out from vision; but if the bullet be adjusted at a greater distance from the eye, then the centre
only will be obscured, and the outer edge or ring of the target remains visible.
When the advancing edge, or first limb, as it is termed, of the moon approaches very near to the
second limb of the sun, the two are joined together for a time by alternations of black and white
points, called Baily's beads.

This phenomenon is supposed to be caused partly by the uneven and mountainous edge of the moon,
and partly by that inevitable fault of telescopes, and of the nervous system of the eye, which tends to
enlarge the images of luminous objects, producing what is called irradiation. It is exceedingly
interesting to know that, although the clouds obscured the annular eclipse of 1858, in many parts of
England, we are yet left the recorded observations of one fortunate astronomer, Mr. John Yeats, who
states that—
"All the phenomena of an annular eclipse were clearly and beautifully visible on the Fotheringay-
Castle-mound, which is a locality easily identified. Baily's beads were perfectly plain on the
completion of the annulus, which occurrence took place, according to my observation, at about
seventy seconds after 1 o'clock; it lasted about eighty seconds. The 'beads,' like drops of water,
appeared on the upper and under sides of the moon, occupying fully three-fourths of her
circumference.
"Prior to this, the upper edge of the moon seemed dark and rough, and there were no other changes of
colour. At 12.43, the cusps, for a few moments, bore a very black aspect.
"There was nothing like intense darkness during the eclipse, and less gloom than during a
thunderstorm. Bystanders prognosticated rain; but it was the shadow of a rapidly-declining day. At 12
o'clock, a lady living on the farm suddenly exclaimed, 'The cows are coming home to be milked!' and
they came, all but one; that followed, however, within the hour. Cocks crowed, birds flew low or
fluttered about uneasily, but every object far and near was well defined to the eye.
"A singular broadway of light stretched north and south for upwards of a quarter of an hour; from
about 12.54 to 1.10 p.m."
If the annular
eclipse of the sun
be a matter for
wonderment, the
total eclipse of the
same is much more
surprising; no other
expression than that
of awfully grand,
can give an idea of
the effects of
totality, and of the
suddenness with Fig. 39.
Fig. 38. which it obscures
the light of heaven. The darkness, it is said, comes dropping
down like a mantle, and as the moment of full obscuration approaches, people's countenances become
livid, the horizon is indistinct and sometimes invisible, and there is a general appearance of horror on
all sides. These are not simply the inventions of active human imaginations, for they produce equal, if
not greater effects, upon the brute creation. M. Arago quotes an instance of a half-starved dog, who
was voraciously devouring some food, but dropped it the instant the darkness came on. A swarm of
ants, busily engaged, stopped when the darkness commenced, and remained motionless till the light
reappeared. A herd of oxen collected themselves into a circle and stood still, with their horns outward,
as if to resist a common enemy; certain plants, such as the convolvulus and silk-tree acacia, closed
their leaves. The latter statement was corroborated during the annular eclipse of the 15th of March,
1858, by Mr. E. S. Lane, who states, that crocuses at the Observatory, Beeston, had their blossoms
expanded before the eclipse; they commenced closing, and were quite shut at about one minute

previous to the greatest darkness; and the flowers opened partially about twenty minutes afterwards. A
"total eclipse" of the sun has always impressed the human mind with terror and wonder in every age:
it was always supposed to be the forerunner of evil; and not only is the mind powerfully impressed, as
darkness gradually shuts out the face of the sun, but at the moment of totality, a magnificent corona, or
glory of light, is visible, and prominences, or flames, as they are often termed, make their appearance
at different points round the circle of the dark mass. This glory does not flash suddenly on the eye; but
commencing at the first limb of the sun, passes quickly from one limb to the other. Our illustration
shows "the corona" and the "rose-coloured prominences," whose nature we shall next endeavour to
explain. Professor Airy describes the change from the last narrow crescent of light to the entire dark
moon, surrounded by a ring of faint light, as most curious, striking, and magical in effect. The
progress of the formation of the corona was seen distinctly. It commenced on the side of the moon
opposite to that at which the sun disappeared, and in the general decay and disease which seemed to
oppress all nature, the moon and the corona appeared almost like a local sore in that part of the sky,
and in some places were seen double. Its texture appeared as if fibrous, or composed of entangled
threads; in other places brushes, or feathers of light proceeded from it, and one estimate calculated the
light at about one-seventh part of a full moon light. The question, whether the corona is concentric
with the sun and moon, was specially mooted by M. Arago, and Professor Baden Powell has produced
such excellent imitations of the "corona" by making opaque bodies occult, or conceal, very bright
points, that it cannot be considered as material or real, although it ought to be remembered that the
best theory of the zodiacal light represents it to be a nebulous mass, increasing in density towards the
sun, and yet no portion of this nebulous mass was seen during the totality. But by far the most
remarkable of all the appearances connected with a "total eclipse" are the rose-coloured prominences,
mountains, or flames, projecting from the circumference of the moon to the inner ring of the corona;
and, although they had been observed by Vaserius (a Swedish astronomer) in 1733, they took the
modern astronomers entirely by surprise in 1842, and they were not prepared with instruments to
ascertain the nature of these strange and almost portentous forms. In 1851, however, great
preparations were made to throw further light on the subject. Professor Airy went to make his
observations, and he says, "That the suddenness of the darkness in 1851 appeared much more striking
than in 1842, and the forms of the rose-coloured mountains were most curious. One reminded him of a
boomerang (that curious weapon thrown so skilfully by the aborigines of Australia); this same figure
has been spoken of by others as resembling a Turkish scimitar, strongly coloured with rose-red at the
borders, but paler in the centre. Another form was a pale-white semicircle based on the moon's limbs;
a third figure was a red detached cloud, or balloon, of nearly circular form, separated from the moon
by nearly its own breadth; a fourth appeared like a small triangle, or conical red mountain, perhaps a
little white in the interior;" and the Professor proceeds to say, "I employed myself in an attempt to
draw roughly the figures, and it was impossible, after witnessing the increase in height of some, and
the disappearance of another, and the arrival of new forms, not to feel convinced that the phenomena
belonged to the sun, and not to the moon."
Still the question remains unanswered, what are these "rose-coloured prominences?" If they belong to
the sun, and are mountains in that luminary, they must be some thirty or forty thousand miles in
height.
M. Faye has formally propounded the theory, that they are caused by refraction, or a kind of mirage,
or the distortion of objects caused by heated air. This phenomenon is not peculiar to any country,
though most frequently observed near the margin of lakes and rivers, and on hot sandy plains. M.
Monge, who accompanied Buonaparte in his expedition to Egypt, witnessed a remarkable example
between Alexandria and Cairo, where, in all directions, green islands appeared surrounded by
extensive lakes of pure, transparent water. M. Monge states that "Nothing could be conceived more
lovely or picturesque than the landscape. In the tranquil surface of the lake, the trees and houses with
which the islands are covered were strongly reflected with vivid and varied hues, and the party

hastened forward to enjoy the refreshment apparently proffered them; but when they arrived, the lake,
on whose bosom the images had floated—the trees, amongst whose foliage they arose, and the people
who stood on the shore, as if inviting their approach, had all vanished, and nothing remained but the
uniform and irksome desert of sand and sky, with a few naked and ragged Arabs."
If M. Monge and his party had not been undeceived, by actually going to the spot, they would, one
and all, have been firmly convinced that these visionary trees, lakes, and buildings had a real
existence. This kind of mirage is known in Persia and Arabia by the name of "serab" or miraculous
water, and in the western districts of India by that of "scheram." This illusion is the effect of unusual
refraction, and M. Faye attempts to account for the rose-coloured mountains by something of a similar
nature.
It is right, however, to mention, that learned astronomers do not consider this theory of any value.
Lieutenant Patterson, one of the observers of the eclipse of 1851, says, that "It is very remarkable that
the flames or prominences correspond exactly (at least as far as he could judge) with the spots on the
sun's surface." Taking this statement with that of M. Faye, it may be assumed, as a new idea, and
nothing more, that these prominences are, after all, mere aerial pictures of these openings in the sun's
atmosphere, or what are called "sun spots." In the "Edinburgh Philosophical Journal," it is said, that
although it has lately been shown in the Edinburgh Observatory that it is possible to produce, by
certain optical experiments, red flames on the sun's limb of precisely the rose-coloured tint described,
yet, on weighing the whole of the evidence, there does seem a great preponderance in favour of the
eclipse flames being real appendages of the sun, and in that case they must be masses of such vast size
as to play no unimportant part in the economy of that stupendous orb.
During the last eclipse great disappointment was felt that the darkness was so insignificant, although,
when we consider the enormous light-giving power of the sun, and know that it was not wholly
obscured, we could hardly have expected any other result. There can be no doubt that a decided
change in the amount of light is only to be observed during a total eclipse of the sun, one of which
occurred on the 7th of September, 1858; but, unfortunately, it was only visible in South America; we
must therefore content ourselves with the descriptions of those astronomers who can be fully relied
on. From the graphic account given by Professor Piazzi Smyth, the astronomer-royal for Scotland, of a
total eclipse as seen by him on the western coast of Norway, we may form some notion of the
imposing appearance of the surrounding country when obscured during the occurrence of this rare
astronomical phenomenon.
The Professor remarks, "To understand the scene more fully, the reader must fancy himself on a small,
rocky island on a mountainous coast, the weather calm, and the sky at the beginning of the eclipse
seven-tenths covered with thin and bright cirro-strati clouds. As the eclipse approaches, the clouds
gradually darken, the rays of the sun are no longer able to penetrate them through and through, and
drench them with living light as before, but they become darker than the sky against which they are
seen. The air becomes sensibly colder, the clouds still darker, and the whole atmosphere murkier.
"From moment to moment as the totality approaches, the cold and darkness advance apace; and there
is something peculiarly and terribly convincing in the two different senses, so entirely coinciding in
their indications of an unprecedented fact being in course of accomplishment. Suddenly, and
apparently without any warning (so immensely greater were its effects than those of anything else
which had occurred), the totality supervenes, and darkness comes down. Then came into view lurid
lights and forms, as on the extinction of candles. This was the most striking point of the whole
phenomenon, and made the Norse peasants about us flee with precipitation, and hide themselves for
their lives.

"Darkness reigned everywhere in heaven and earth, except where, along the north-eastern horizon, a
narrow strip of unclouded sky presented a low burning tone of colour, and where some distant snow-
covered mountains, beyond the range of the moon's shadow, reflected the faint mono-chromatic light
of the partially eclipsed sun, and exhibited all the detail of their structure, all the light, and shade, and
markings of their precipitous sides with an apparently supernatural distinctness. After a little time, the
eyes seemed to get accustomed to the darkness, and the looming forms of objects close by could be
discerned, all of them exhibiting a dull-green hue; seeming to have exhaled their natural colour, and to
have taken this particular one, merely by force of the red colour in the north.
"Life and animation seemed, indeed, to have now departed from everything around, and we could
hardly but fear, against our reason, that if such a state of things was to last much longer, some dreadful
calamity must happen to us all; while the lurid horizon, northward, appeared so like the gleams of
departing light in some of the grandest paintings by Danby and Martin, that we could not but believe,
in spite of the alleged extravagances of these artists, that Nature had opened up to the constant
contemplation of their mind's-eye some of those magnificent revelations of power and glory which
others can only get a glimpse of on occasions such as these."
It can be easily imagined, that under such peculiar and awful circumstances, the careful observation of
these effects must be somewhat difficult, and the only wonder is that the astronomical observations are
conducted with any certainty at all.
In the eclipse of 1842, it was not only the vivacious Frenchman who was carried away in the impulse
of the moment, and had afterwards to plead that "he was no more than a man" as an excuse for his
unfulfilled part in the observations, but the same was the case with the grave Englishman and the more
stolid German. In 1851, much the same failure in the observations occurred; and on some person
asking a worthy American, who had come with his instruments from the other side of the world
expressly to observe the eclipse, what he had succeeded in doing? he merely answered, with much
quiet impressiveness, "That if it was to be observed over again, he hoped he would be able to do
something, but that, as it was, he had done nothing: it had been too much for him." This is not quite so
bad as the fashionable lady who had been invited to look at an eclipse of the sun through a grand
telescope, but arriving too late, inquired whether "it could not be shown over again."
With this brief glance at the science of astronomy, we once more return to the term "gravity," which
will introduce to us some new and interesting facts, under the head of what is called "centre of
gravity."

CHAPTER IV.
CENTRE OF GRAVITY.

That point about which all the parts of a body do, in any situation, exactly balance each other.
The discovery of this fact is due to Archimedes, and it is a point in every solid body (whatever the
form may be) in which the forces of gravity may be considered as united. In our globe, which is a
sphere, or rather an oblate spheroid, the centre of gravity will be the centre. Thus, if a plummet be
suspended on the surface of the earth, it points directly to the centre of gravity, and, consequently, two
plummet-lines suspended side by side cannot, strictly speaking, be parallel to each other.

Fig. 40.

f. The centre. a b c d e. Plummet-lines, all pointing to the centre, and therefore diverging from each other.

If it were possible to bore or dig a gallery through the whole substance of the earth from pole to pole,
and then to allow a stone or the fabled Mahomet's coffin to fall through it, the momentum—i.e., the
force of the moving body, would carry it beyond the centre of gravity. This force, however, being
exhausted, there would be a retrograde movement, and after many oscillations it would gradually
come to rest, and then, unsupported by anything material, it would be suspended by the force of
gravitation, and now enter into and take part in the general attracting force; and being equally attracted
on every side, the stone or coffin must be totally without weight.
Momentum is prettily illustrated by a series of inclined planes cut in mahogany, with a grooved
channel at the top, in imitation of the famous Russian ice mountains: and if a marble is allowed to run
down the first incline, the momentum will carry it up the second, from which it will again descend and
pass up and down the third and last miniature mountain.

Fig. 41.
p p p. Inclined planes, gradually decreasing in height, cut out of inch mahogany, with a groove at the top to carry an
ordinary marble. b b b. Different positions of the marble, which starts from b a.

In a sphere of uniform density, the centre of gravity is easily discovered, but not so in an irregular
mass; and here, perhaps, an explanation of terms may not be altogether unacceptable.
Mass, is a term applied to solids, such as a mass of lead or stone.
Bulk, to liquids, such as a bulk of water or oil.
Volume, to gases, such as a volume of air or oxygen.

Fig. 42.
a b d, The three points of suspension. c, The point of intersection, and, therefore, the centre of gravity. p, The line of
plummet.

To find the centre of gravity of any mass, as, for example, an ordinary school-slate, we must first of all
suspend it from any part of the frame; then allow a plumb-line to drop from the point of suspension,
and mark its direction on the slate. Again, suspend the slate at various other points, always marking
the line of direction of the plummet, and at the point where the lines intersect each other, there will be
the centre of gravity.
If the slate be now placed (as shown in Fig. 43) on a blunt wooden point at the spot where the lines
cross each other, it will be found to balance exactly, and this place is called the centre of gravity, being
the point with which all other particles of the body would move with parallel and equable motion
during its fall. The equilibrium of bodies is therefore much affected by the position of the centre of
gravity. Thus, if we cut out an elliptical figure from a board one inch in thickness, and rest it on a flat
surface by one of its edges (as at No. 1, fig. 44), this point of contact is called the point of support, and
the centre of gravity is immediately above it.
In this case, the body is in a state of secure equilibrium, for any motion on
either side will cause the centre of gravity to ascend in these directions,
and an oscillation will ensue. But if we place it upon the smaller end, as
shown at No. 2 (fig. 44), the position will be one of equilibrium, but not
stable or secure; although the centre of gravity is directly above the point
of support, the slightest touch will displace the oval and cause its
overthrow. The famous story of Columbus and the egg suggests a capital
illustration of this fact; and there are two modes in which the egg may be
poised on either of the ends.

Fig. 43.

Fig. 44.
The point of support. c, The centre of gravity.

The one usually attributed to the great discoverer, is that of scraping or slightly breaking away a little
of the shell, so as to flatten one of the ends, thus—

Fig. 45.
a Represents the egg in its natural state, and, therefore, in unstable equilibrium; b, another egg, with the surface, s,
flattened, by which the centre of gravity is lowered, and if not disturbed beyond the extent of the point of support
the equilibrium is stable.

The most philosophical mode of making the egg stand on its end and without disturbing the exterior
shell is to alter the position of the yolk, which has a greater density than the white, and is situated
about the centre. If the egg is now shaken so as to break the membrane enclosing the yolk, and thus
allow it to sink to the bottom of the smaller end, the centre of gravity is lowered; there is a greater
proportion of weight concentrated in the small end, and the egg stands erect, as depicted at fig. 46.

Fig. 46.
No. 1. Section of egg. c. Centre of gravity. y. The yolk. w. The white. No. 2. c. Centre of gravity, much lowered. y.
The yolk at the bottom of the egg.

It is this variable position of the centre of gravity in ivory balls (one part of which may be more dense
than another) that so frequently annoys even the best billiard-players; and on this account a ball will
deviate from the line in which it is impelled, not from any fault of the player, but in consequence of
the ivory ball being of unequal density, and, therefore, not having the centre corresponding with the
centre of gravity. A good billiard-player should, therefore, always try the ball before he engages to
play for any large sum.
The toy called the "tombola" reminds us of the egg-experiment, as there is usually a lump of lead
inserted in the lower part of the hemisphere, and when the toy is pushed down it rapidly assumes the
upright position because the centre of gravity is not in the lowest place to which it can descend; the
latter position being only attained when the figure is upright.

Fig. 47.
No. 1. c. Centre of gravity in the lowest place, figure upright. No. 2. c. Centre of gravity raised as the figure is
inclined on either side, but falling again into the lowest place as the figure gradually comes to rest.

There is a popular paradox in mechanics—viz., "a body having a tendency to fall by its own weight,
may be prevented from falling by adding to it a weight on the same side on which it tends to fall," and
the paradox is demonstrated by another well-known child's toy as depicted in the next cut.

Fig. 48.
The line of direction falling beyond the base; the bent wire and lead weight throwing the centre of gravity under the
table and near the leaden weight; the hind legs become the point of support, and the toy is perfectly balanced.

Fig. 49.
No. 1. Sword balanced on handle: the arc from c to d is very small, and if the centre, c, falls out of the line of
direction it is not easily restored to the upright position. No 2. Sword balanced on the point: the arc from c to d
much larger, and therefore the sword is more easily balanced.

After what has been explained regarding the improvement of the stability of the egg by lowering the
situation of the centre of gravity, it may at first appear singular that a stick loaded with a weight at its
upper extremity can be balanced perpendicularly with greater ease and precision than when the weight
is lower down and nearer the hand; and that a sword can be balanced best when the hilt is uppermost;
but this is easily explained when it is understood that with the handle downwards a much smaller arc
is described as it falls than when reversed, so that in the former case the balancer has not time to re-
adjust the centre, whilst in the latter position the arc described is so large that before the sword falls
the centre of gravity may be restored within the line of direction of the base.
For the same reason, a child tripping against a stone will fall quickly; whereas, a man can recover
himself; this fact can be very nicely shown by fixing two square pieces of mahogany of different
lengths, by hinges on a flat base or board, then if the board be pushed rapidly forward and struck
against a lead weight or a nail put in the table, the short piece is seen to fall first and the long one
afterwards; the difference of time occupied in the fall of each piece of wood (which may be carved to
represent the human figure) being clearly denoted by the sounds produced as they strike the board.

Fig. 50.
No. 1. The two pieces of mahogany, carved to represent a man and a boy, one being 10 and the other 5 inches long,
attached to board by hinges at h h.

Fig. 51.
No. 2. The board pushed forward, striking against a nail, when the short piece falls first, and the long one second.

Boat-accidents frequently arise in consequence of ignorance on the subject of the centre of gravity,
and when persons are alarmed whilst sitting in a boat, they generally rise suddenly, raise the centre of
gravity, which falling, by the oscillation of the frail bark, outside the line of direction of the base,
cannot be restored, and the boat is upset; if the boat were fixed by the keel, raising the centre of
gravity would be of little consequence, but as the boat is perfectly free to move and roll to one side or
the other, the elevation of the centre of gravity is fatal, and it operates just as the removal of the lead
would do, if changed from the base to the head of the "tombola" toy.
A very striking experiment, exhibiting the danger of rising in a boat, maybe shown by the following
model, as depicted at Nos. 1 and 2, figs. 52 and 53.

Fig. 52.
No. 1. Sections of a toy-boat floating in water. b b b. Three brass wires placed at regular distances and screwed into
the bottom of the boat, with cuts or slits at the top so that when the leaden bullets, l l l, which are perforated and
slide upon them like beads, are raised to the top, they are retained by the brass cuts springing out; when the bullets
are at the bottom of the lines they represent persons sitting in a boat, as shown in the lower cuts, and the centre of
gravity will be within the vessel.

We thus perceive that the stability of a body placed on a base depends upon the position of the line of
direction and the height of the centre of gravity.
Security results when the line of direction falls within the base. Instability when just at the edge.
Incapability of standing when falling without the base.

Fig. 53.
No. 2. The leaden bullets raised to the top now show the result of persons suddenly rising, when the boat
immediately turns over, and either sinks or floats on the surface with the keel upwards.

The leaning-tower of Pisa is one hundred and eighty-two feet in height, and is swayed thirteen and a
half feet from the perpendicular, but yet remains perfectly firm and secure, as the line of direction falls
considerably within the base. If it was of a greater altitude it could no longer stand, because the centre
of gravity would be so elevated that the line of direction would fall outside the base. This fact may be
illustrated by taking a board several feet in length, and having cut it out to represent the architecture of
the leaning-tower of Pisa, it may then be painted in distemper, and fixed at the right angle with a hinge
to another board representing the ground, whilst a plumb-line may be dropped from the centre of
gravity; and it may be shown that as long as the plummet falls within the base, the tower is safe; but
directly the model tower is brought a little further forward by a wedge so that the plummet hangs
outside, then, on removing the support, which may be a piece of string to be cut at the right moment,
the model falls, and the fact is at once comprehended.

Fig. 54.
f. Board cut and painted to represent the leaning-tower of Pisa. g. The centre of gravity and plummet line suspended
from it. h. The hinge which attaches it to the base board. i. The string, sufficiently long to unwind and allow the
plummet to hang outside the base, so that, when cut, the model falls in the direction of the arrow.

The leaning-towers of Bologna are likewise celebrated for their great inclination; so also (in England)
is the hanging-tower, or, more correctly, the massive wall which has formed part of a tower at
Bridgenorth, Salop; it deviates from the perpendicular, but the centre of gravity and the line of
direction fall within the base, and it remains secure; indeed, so little fears are entertained of its
tumbling down, that a stable has been erected beneath it.

Fig. 55.
No. 1. Two billiard-cues arranged for the experiment and fixed to a board: the ball is rolling up. No. 2. Sections
showing that the centre of gravity, c, is higher at a than at b, which represents the thick end of the cues; it therefore,
in effect, rolls down hill.

One of the most curious paradoxes is displayed in the ascent of a billiard-ball from the thin to the thick
ends of two billiard-cues placed at an angle, as in our drawing above; here the centre of gravity is
raised at starting, and the ball moves in consequence of its actually falling from the high to the low
level.
Much of the stability of a body depends on the height through which the centre of gravity must be
elevated before the body can be overthrown. The greater this height, the greater will be the
immovability of the mass. One of the grandest examples of this fact is shown in the ancient Pyramids;
and whilst gigantic palaces, with vast columns, and all the solid grandeur belonging to Egyptian
architecture, have succumbed to time and lie more or less prostrate upon the earth, the Pyramids, in
their simple form and solidity, remain almost as they were built, and it will be noticed, in the
accompanying sketch, how difficult, if not impossible, it would be to attempt to overthrow bodily one
of these great monuments of ancient times.

Fig. 56.

c. Centre of gravity, which must be raised to d before it can be overthrown.

The principles already explained are directly applicable to the construction or secure loading of
vehicles; and in proportion as the centre of gravity is elevated above the point of support (that is, the
wheels), so is the insecurity of the carriage increased, and the contrary takes place if the centre of
gravity is lowered. Again, if a waggon be loaded with a very heavy substance which does not occupy
much space, such as iron, lead, or copper, or bricks, it will be in much less danger of an overthrow
than if it carries an equal weight of a lighter body, such as pockets of hops, or bags of wool or bales of
rags.

Fig. 57.
No. 1. The centre of gravity is near the ground, and falls within the wheels. No. 2. The centre of gravity is much
elevated, and the line of direction is outside the wheels.

In the one instance, the centre of gravity is near the ground, and falls well within the base, as at No. 1,
fig. 57. In the other, the centre of gravity is considerably elevated above the ground, and having met
with an obstruction which has raised one side higher than the other, the line of direction has fallen
outside the wheels, and the waggon is overturning as at No. 2.
The various postures of the human body may be regarded as so many experiments upon the position of
the centre of gravity which we are every moment unconsciously performing.
To maintain an erect position, a man must so place his body as to cause the line of direction of his
weight to fall within the base formed by his feet.

Fig. 58.
The more the toes are turned outwards, the more contracted will be the base, and the body will be
more liable to fall backwards or forwards; and the closer the feet are drawn together, the more likely is
the body to fall on either side. The acrobats, and so-called "India-Rubber Brothers," dancing dogs,
&c., unconsciously acquire the habit of accurately balancing themselves in all kinds of strange
positions; but as these accomplishments are not to be recommended to young people, some other
marvels (such as balancing a pail of water on a stick laid upon a table) may be adduced, as illustrated
in fig. 59.

Fig. 59.
Let a b represent an ordinary table, upon which place a broomstick, c d, so that one-half shall lay upon
the table and the other extend from it; place over the stick the handle of an empty pail (which may
possibly require to be elongated for the experiment) so that the handle touches or falls into a notch at
h; and in order to bring the pail well under the table, another stick is placed in the notch e, and is
arranged in the line g f e, one end resting at g and the other at e. Having made these preparations, the
pail may now be filled with water; and although it appears to be a most marvellous result, to see the
pail apparently balanced on the end of a stick which may easily tilt up, the principles already

explained will enable the observer to understand that the centre of gravity of the pail falls within the
line of direction shown by the dotted line; and it amounts in effect to nothing more than carrying a pail
on the centre of a stick, one end of which is supported at e, and the other through the medium of the
table, a b.
This illustration may be modified by using a heavy weight, rope, and stick, as shown in our sketch
below.

Fig. 60.
Before we dismiss this subject it is advisable to explain a term referring to a very useful truth, called
the centre of percussion; a knowledge of which, gained instinctively or otherwise, enables the
workman to wield his tools with increased power, and gives greater force to the cut of the swordsman,
so that, with some physical strength, he may perform the feat of cutting a sheep in half, cleaving a bar
of lead, or neatly dividing, à la Saladin, in ancient Saracen fashion, a silk handkerchief floating in the
air. There is a feat, however, which does not require any very great strength, but is sufficiently
startling to excite much surprise and some inquiry—viz., the one of cutting in half a broomstick
supported at the ends on tumblers of water without spilling the water or cracking or otherwise
damaging the glass supports.

Fig. 61.
These and other feats are partly explained by reference to time: the force is so quickly applied and
expended on the centre of the stick that it is not communicated to the supports; just as a bullet from a
pistol may be sent through a pane of glass without shattering the whole square, but making a clean
hole through it, or a candle may be sent through a plank, or a cannon-ball pass through a half opened
door without causing it to move on its hinges. But the success of the several feats depends in a great
measure on the attention that is paid to the delivery of the blows at the centre of percussion of the
weapon; this is a point in a moving body where the percussion is the greatest, and about which the
impetus or force of all parts is balanced on every side. It may be better understood by reference to our
drawing below. Applying this principle to a model sword made of wood, cut in half in the centre of the
blade, and then united with an elbow-joint, the handle being fixed to a board by a wire passed through
it and the two upright pieces of wood, the fact is at once apparent, and is well shown in Nos. 1, 2, 3,
fig. 62.

Fig. 62.
No. 1, is the wooden sword, with an elbow-joint at c. No. 2. Sword attached to board at k, and being allowed to fall
from any angle shown by dotted-line, it strikes the block, w, outside the centre of percussion, p, and as there is
unequal motion in the parts of the sword it bends down (or, as it were, breaks) at the elbow-joint, c. No. 3 displays
the same model; but here the blow has fallen on the block, w, precisely at the centre of percussion of the sword, p,
and the elbow-joint remains perfectly firm.

When a blow is not delivered with a stick or sword at the centre of percussion, a peculiar jar, or what
is familiarly spoken of as a stinging sensation, is apparent in the hand; and the cause of this
disagreeable result is further elucidated by fig. 63, in which the post, a, corresponds with the handle of
the sword.

Fig. 63.
a. The post to which a rope is attached. b and c are two horses running round in a circle, and it is plain that b will
not move so quick as c, and that the latter will have the greatest moving force; consequently, if the rope was
suddenly checked by striking against an object at the centre of gravity, the horse c would proceed faster than b, and
would impart to b a backward motion, and thus make a great strain on the rope at a. But if the obstacle were placed
so as to be struck at a certain point nearer c, viz., at or about the little star, the tendency of each horse to move on
would balance and neutralize the other, so that there would be no strain at a. The little star indicates the centre of
percussion.

All military men, and especially those young gentlemen who are intended for the army, should bear in
mind this important truth during their sword-practice; and with one of Mr. Wilkinson's swords, made
only of the very best steel, they may conquer in a chance combat which might otherwise have proved
fatal to them. To Mr. Wilkinson, of Pall Mall, the eminent sword-cutler, is due the great merit of
improving the quality of the steel employed in the manufacture of officers' swords; and with one of his
weapons, the author has repeatedly thrust through an iron plate about one-eighth of an inch in
thickness without injuring the point, and has also bent one nearly double without fracturing it, the
perfect elasticity of the steel bringing the sword straight again. These, and other severe tests applied to
Wilkinson's swords, show that there is no reason why an officer should not possess a weapon that will
bear comparison with, nay, surpass, the far-famed Toledo weapon, instead of submitting to mere army-
tailor swords, which are often little better than hoops of beer barrels; and, in dire combat with Hindoo
or Mussulman fanatics' Tulwah, may show too late the folly of the owner.

Fig. 64.

CHAPTER V.
SPECIFIC GRAVITY.

It is recorded of the great Dr. Wollaston, that when Sir Humphry Davy placed in his hand, what was
then considered to be the scientific wonder of the day—viz., a small bit of the metal potassium, he
exclaimed at once, "How heavy it is," and was greatly surprised, when Sir Humphry threw the metal
on water, to see it not only take fire, but actually float upon the surface; here, then, was a philosopher
possessing the deepest learning, unable, by the sense of touch and by ordinary handling, to state
correctly whether the new substance (and that a metal), was heavy or light; hence it is apparent that
the property of specific gravity is one of importance, and being derived from the Latin, means species,
a particular sort or kind; and gravis, heavy or weight—i.e., the particular weight of every substance
compared with a fixed standard of water.

Fig. 65.
a. A large cylindrical vessel containing water, in which the egg sinks till it reaches the bottom of the glass. b. A
similar glass vessel containing half brine and half water, in which the egg floats in the centre—viz., just at the point
where the brine and water touch.

We are so constantly in the habit of referring to a standard of perfection in music and the arts of
painting and sculpture, that the youngest will comprehend the office of water when told that it is the
philosopher's unit or starting-point for the estimation of the relative weights of solids and liquids. A
good idea of the scope and meaning of the term specific gravity, is acquired by a few simple
experiments, thus: if a cylindrical glass, say eighteen inches long, and two and a half wide, is filled
with water, and another of the same size is also filled, one half with water and the other half with a

saturated solution of common salt, or what is commonly termed brine, a
most amusing comparison of the relative weights of equal bulks of water
and brine, can be made with the help of two eggs; when one of the eggs is
placed in the glass containing water, it immediately sinks to the bottom,
showing that it has a greater specific gravity than water; but when the other
egg is placed in the second glass containing the brine, it sinks through the
water till it reaches the strong solution of salt, where it is suspended, and
presents a most curious and pretty appearance; seeming to float like a
balloon in air, and apparently suspended upon nothing, it provokes the
inquiry, "whether magnetism has anything to do with it?" The answer, of
course, is in the negative, it merely floats in the centre, in obedience to the
common principle, that all bodies float in others which are heavier than
themselves; the brine has, therefore, a greater weight than an equal bulk of
water, and is also heavier than the egg. A pleasing sequel to this
experiment may be shown by demonstrating how the brine is placed in the
vessel without mixing with the water above it; this is done by using a glass
tube and funnel, and after pouring away half the water contained in the
vessel (Fig. 65), the egg can be floated from the bottom to the centre of the
glass, by pouring the brine down the funnel and tube. The saturated
solution of salt remains in the lower part of the vessel and displaces the
water, which floats upon its surface like oil on water, carrying the egg with
it.
The water of the Dead Sea is said to contain about twenty-six per cent. of
saline matter, which chiefly consists of common salt. It is perfectly clear
and bright, and in consequence of the great density, a person may easily
float on its surface, like the egg on the brine, so that if a ship could be
Fig. 66.
heavily laden whilst floating on the water of the Dead Sea, it would most
likely sink if transported to the Thames. This illustration of specific gravity A vessel half full of water, and
is also shown by a model ship, which being first floated on the brine, will as the brine is poured down the
afterwards sink if conveyed to another vessel containing water. One of the tube the egg gradually rises.
tin model ships sold as a magnetic toy answers nicely for this experiment,
but it must be weighted or adjusted so that it just floats in the brine, a; then
it will sink, when placed, in another vessel containing only water.

Fig. 67.
a. Vessel containing brine, upon which the little model floats. b. Vessel containing water, in which the ship sinks.

Another amusing illustration of the same kind is displayed with goldfish, which swim easily in water,
floating on brine, but cannot dive to the bottom of the vessel, owing to the density of the saturated
solution of salt. If the fish are taken out immediately after the experiment, and placed in fresh water,
they will not be hurt by contact with the strong salt water.
These examples of the relative weights of equal bulks, enable the youthful mind to grasp the more
difficult problem of ascertaining the specific gravity of any solid or liquid substance; and here the
strict meaning of terms should not be passed by. Specific weight must not be confounded with
Absolute weight; the latter means the entire amount of ponderable matter in any body: thus, twenty-
four cubic feet of sand weigh about one ton, whilst specific weight means the relation that subsists
between the absolute weight and the volume or space which that weight occupies. Thus a cubic foot of
water weighs sixty-two and a half pounds, or 1000 ounces avoirdupois, but changed to gold, the cubic
foot weighs more than half a ton, and would be equal to about 19,300 ounces—hence the relation
between the cubic foot of water and that of gold is nearly as 1 to 19.3; the latter is therefore called the
specific gravity of gold.
Such a mode of taking the specific gravity of different substances—viz., by the weight of equal bulks,
whether cubic feet or inches, could not be employed in consequence of the difficulty of procuring
exact cubic inches or feet of the various substances which by their peculiar properties of brittleness or
hardness would present insuperable obstacles to any attempt to fashion or shape them into exact
volumes. It is therefore necessary to adopt the method first devised by Archimedes, 600 b.c., when he
discovered the admixture of another metal with the gold of King Hiero's crown.

This amusing story, ending in the discovery of a philosophical truth, may be thus described:—King
Hiero gave out from the royal treasury a certain quantity of gold, which he required to be fashioned
into a crown; when, however, the emblem of power was produced by the goldsmith, it was not found
deficient in weight, but had that appearance which indicated to the monarch that a surreptitious
addition of some other metal must have been made.
It may be assumed that King Hiero consulted his friend and philosopher Archimedes, and he might
have said, "Tell me, Archimedes, without pulling my crown to pieces, if it has been adulterated with
any other metal?" The philosopher asked time to solve the problem, and going to take his accustomed
bath, discovered then specially what he had never particularly remarked before—that, as he entered
the vessel of water, the liquid rose on each side of him—that he, in fact, displaced a certain quantity of
liquid. Thus, supposing the bath to have been full of water, directly Archimedes stepped in, it would
overflow. Let it be assumed that the water displaced was collected, and weighed 90 pounds, whilst the
philosopher had weighed, say 200 pounds. Now, the train of reasoning in his mind might be of this
kind:—"My body displaces 90 pounds of water; if I had an exact cast of it in lead, the same bulk and
weight of liquid would overflow; but the weight of my body was, say 200 pounds, the cast in lead
1000 pounds; these two sums divided by 90 would give very different results, and they would be the
specific gravities, because the rule is thus stated:—'Divide the gross weight by the loss of weight in
water, the water displaced, and the quotient gives the specific gravity.'" The rule is soon tested with the
help of an ordinary pair of scales, and the experiment made more interesting by taking a model crown
of some metal, which may be nicely gilt and burnished by Messrs. Elkington, the celebrated electro-
platers of Birmingham. For convenience, the pan of one scale is suspended by shorter chains than the
other, and should have a hook inserted in the middle; upon this is placed the crown, supported by very
thin copper wire. For the sake of argument, let it be supposed that the crown weighs 17½ ounces
avoirdupois, which are duly placed in the other scale-pan, and without touching these weights, the
crown is now placed in a vessel of water. It might be supposed that directly the crown enters the water,
it would gain weight, in consequence of being wetted, but the contrary is the case, and by thrusting the
crown into the water, it may be seen to rise with great buoyancy so long as the 17½ ounces are
retained in the other scale-pan; and it will be found necessary to place at least two ounces in the scale-
pan to which the crown is attached before the latter sinks in the water; and thus it is distinctly shown
that the crown weighs only about 15½ ounces in the water, and has therefore lost instead of gaining
weight whilst immersed in the liquid. The rule may now be worked out:

Ounces.
Weight of crown in air 17½
Ditto in water 15½
———
Less in water 2
———
17½ / 2 = 8·75

The quotient 8¾ demonstrates that the crown is manufactured of copper, because it would have been
about 19¼ if made of pure gold.

Fig. 68.
a. Ordinary pair of scales. b. Scale-pan, containing 17½ ounces, being the weight of the crown in air. c. Pan, with
hook and crown attached, which is sunk in the water contained in the vessel d; this pan contains the two ounces,
which must be placed there to make the crown sink and exactly balance b.

Table of the Specific Gravities of the Metals in common use.

Platinum 20.98
Gold 19.26 to 19.3 and 19.64
Mercury 13.57
Lead 11.35
Silver 10.47 to 10.5
Bismuth 9.82
Copper 8.89
Iron 7.79
Tin 7.29
Zinc 6.5 to 7.4

The simple rule already explained may be applied to all metals of any size or weight, and when the
mass is of an irregular shape, having various cavities on the surface, there may be some difficulty in
taking the specific gravity, in consequence of the adhesion of air-bubbles; but this may be obviated
either by brushing them away with a feather, or, what is frequently much better, by dipping the metal
or mineral first into alcohol, and then into water, before placing it in the vessel of water, by which the
actual specific gravity is to be taken.
The mode of taking the specific gravity of liquids is very simple, and is usually performed in the
laboratory by means of a thin globular bottle which holds exactly 1000 grains of pure distilled water at
60° Fahrenheit. A little counterpoise of lead is made of the exact weight of the dry globular bottle, and
the liquid under examination is poured into the bottle and up to the graduated mark in the neck; the

bottle is then placed in one scale-pan, the counterpoise and the 1000-grain weight in the other; if the
liquid (such as oil of vitriol) is heavier than water, then more weight will be required—viz., 845 grains
—and these figures added to the 1000 would indicate at once that the specific gravity of oil of vitriol
was 1.845 as compared with water, which is 1.000. When the liquid, such as alcohol, is lighter than
water, the 1000-grain weight will be found too much, and grain weights must be added to the same
scale-pan in which the bottle is standing, until the two are exactly balanced. If ordinary alcohol is
being examined, it will be found necessary to place 180 grains with the bottle, and these figures
deducted from the 1000 grains in the other scale-pan, leave 820, which, marked with a dot before the
first figure (sic .820), indicates the specific gravity of alcohol to be less than that of water.
The difference in the gravities of various liquids is displayed in a very pleasing manner by an
experiment devised by Professor Griffiths, to whom chemical lecturers are especially indebted for
some of the most ingenious and beautiful illustrations which have ever been devised. The experiment
consists in the arrangement of five distinct liquids of various densities and colours, the one resting on
the other, and distinguished not only by the optical line of demarcation, but by little balls of wax,
which are adjusted by leaden shot inside, so as to sink through the upper strata of liquids, and rest only
upon the one that it is intended to indicate.
The manipulation for this experiment is somewhat troublesome, and is commenced by procuring some
pure bright quicksilver, upon which an iron bullet (black-leaded, or painted of any colour) is placed, or
one of those pretty glass balls which are sold in such quantities at the Crystal Palace.
Secondly. Put as much white vitriol (sulphate of zinc) into a half pint of boiling water as it will
dissolve, and, when cold, pour off the clear liquid, make up a ball of coloured wax (say red), and
adjust it by placing little shot inside, until it sinks in a solution of sulphate of copper and floats on that
of the white vitriol.
Thirdly. Make a solution of sulphate of copper in precisely the same manner, and adjust another wax
ball to sink in water, and float on this solution.
Fourthly. Some clear distilled water must be provided.
Fifthly. A little cochineal is to be dissolved in some common spirits of wine (alcohol), and a ball of
cork painted white provided.
Finally. A long cylindrical glass, at least eighteen inches high, and two and a half or three inches
diameter, must be made to receive these five liquids, which are arranged in their proper order of
specific gravity by means of a long tube and funnel.
The four balls—viz., the iron, the two wax, and the cork balls, are allowed to slide down the long
glass, which is inclined at an angle; and then, by means of the tube and funnel, pour in the tincture of
cochineal, and all the balls will remain at the bottom of the glass. The water is poured down next, and
now the cork ball floats up on the water, and marks the boundary line of the alcohol and water. Then
the solution of blue vitriol, when a wax ball floats upon it. Thirdly, the solution of white vitriol, upon
which the second wax ball takes its place; and lastly, the quicksilver is poured down the tube, and
upon this heavy metallic fluid the iron or glass ball floats like a cork on water.

The tube may now be carefully removed, pausing at each liquid, so that
no mixture take place between them; and the result is the arrangement of
five liquids, giving the appearance of a cylindrical glass painted with
bands of crimson, blue, and silver; and the liquids will not mingle with
each other for many days.
A more permanent arrangement can be devised by using liquids which
have no affinity, or will not mix with each other—such as mercury,
water, and turpentine.
The specific weight or weights of an equal measure of air and other
gases is determined on the same principle as liquids, although a different
apparatus is required. A light capped glass globe, with stop-cock, from
50 to 100 cubic inches capacity, is weighed full of air, then exhausted by
an air-pump, and weighed empty, the loss being taken as the weight of
its volume of air; these figures are carefully noted, because air instead of
water is the standard of comparison for all gases. When the specific
gravity of any other gas is to be taken, the glass globe is again
exhausted, and screwed on to a gas jar provided with a proper stop-cock,
in which the gas is contained; and when perfect accuracy is required, the
gas must be dried by passing it over some asbestos moistened with oil of
vitriol, and contained in a glass tube, and the gas jar should stand in a
mercurial trough. (Fig. 70.) The stop-cocks are gradually turned, and the
gas admitted to the exhausted globe from the gas jar; when full, the
cocks are turned off, the globe unscrewed, and again weighed, and by
the common rule of proportion, as the weight of the air first found is to
the weight of the gas, so is unity (1.000, the density of air) to a number
which expresses the density of the gas required. If oxygen had been the
Fig. 69. gas tried, the number would be 1.111, being the specific gravity of that
gaseous element. If chlorine, 2.470. Carbonic acid, 1.500. Hydrogen
Long cylindrical glass, 18 × 3 inches, containing being much less than air, the number would only be 69, or decimally
the five liquids. 0.069.

Fig. 70.
a. Glass globe to contain the gas. b. Gas jar standing in the mercurial trough, d. c. Tube containing asbestos moistened with oil
of vitriol.

A very good approximation to the correct specific gravity (particularly where a number of trials have to be made
with the same gas, such as ordinary coal gas) is obtained by suspending a light paper box, with holes at one end,

on one arm of a balance, and a counterpoise on the other. The box can be made carefully, and should have a
capacity equal to a half or quarter cubic foot; it is suspended with the holes downward, and is filled by blowing
in the coal gas until it issues from the apertures, and can be recognised by the smell. The rule in this case would
be equally simple: as the known weight of the half or quarter cubic foot of common air is to the weight of the
coal gas, so is 1.000 to the number required. (Fig. 71.)

Fig. 71.
a. The balance. b. The paper box, of a known capacity. c. Gas-pipe blowing in coal-gas, the arrows showing entrance of gas and
exit of the air.

As an illustration of the different specific weights of the gases, a small
balloon, containing a mixture of hydrogen and air, may be so adjusted
that it will just sink in a tall glass shade inverted and supported on a pad
made of a piece of oilcloth shaped round and bound with list. On passing
in quickly a large quantity of carbonic acid, the little balloon will float
on its surface; and if another balloon, containing only hydrogen, is held
in the top part of the open shade, and a sheet of glass carefully slid over
the open end, the density of the gases (although they are perfectly
invisible) is perfectly indicated; and, as a climax to the experiment, a
third balloon can be filled with laughing gas, and may be placed in the
glass shade, taking care that the one full of pure hydrogen does not
escape; the last balloon will sink to the bottom of the jar, because
laughing gas is almost as heavy as carbonic acid, and the weight of the Fig. 72.
balloon will determine its descent. (Fig. 72.) Inverted large glass shade, containing half
carbonic acid and half common air.

Fig. 73.
a. Inverted glass shade, containing the material, b, for generating carbonic acid gas. c. The soap-bubble. d d. The glass tube for
blowing the bubbles. e. Small lantern, to throw a bright beam of light from the oxy-hydrogen jet upon the thin soap-bubble,
which then displays the most beautiful iridescent colours.

A soap-bubble will rest most perfectly on a surface of carbonic acid gas, and the aerial and elastic cushion
supports the bubble till it bursts. The experiment is best performed by taking a glass shade twelve inches broad
and deep in proportion, and resting it on a pad; half a pound of sesquicarbonate of soda is then placed in the
vessel, and upon this is poured a mixture of half a pint of oil of vitriol and half a pint of water, the latter being
previously mixed and allowed to cool before use. An enormous quantity of carbonic acid gas is suddenly
generated, and rising to the edge, overflows at the top of the glass shade. A well-formed soap-bubble, detached
neatly from the end of a glass-tube, oscillates gently on the surface of the heavy gas, and presents a most curious
and pleasing appearance. The soapy water is prepared by cutting a few pieces of yellow soap, and placing them
in a two-ounce bottle containing distilled water. (Fig. 73.) The specific gravity of the gases, may therefore be
either greater, or less than atmospheric air, which has been already mentioned as the standard of comparison, and
examined by this test the vapours of some of the compounds of carbon and hydrogen are found to possess a
remarkably high gravity; in proof of which, the vapour of ether may be adduced as an example, although it does
not consist only of the two elements mentioned, but contains a certain quantity of oxygen. In a cylindrical tin
vessel, two feet high and one foot in diameter, place an ordinary hot-water plate, of course full of boiling water;
upon this warm surface pour about half an ounce of the best ether; and, after waiting a few minutes until the
whole is converted into vapour, take a syphon made of half-inch pewter tube, and warm it by pouring through it
a little hot water, taking care to allow the water to drain away from it before use. After placing the syphon in the
tin vessel, a light may be applied to the extremity of the long leg outside the tin vessel, to show that no ether is
passing over until the air is sucked out as with the water-syphon; and after this has been done, several warm
glass vessels may be filled with this heavy vapour of ether, which burns on the application of flame. Finally, the
remainder of the vapour may be burnt at the end of the syphon tube, demonstrating in the most satisfactory
manner that the vapour is flowing through the syphon just as spirit is removed by the distillers from the casks
into cellars of the public-houses. (Fig. 74.)

Fig. 74.
a. Tin vessel containing the hot-water plate, b, upon which the ether is poured. c. The syphon. d. Glass to receive the vapour.
e. Combustion of the ether vapour in another vessel.

Before dismissing the important subject of specific gravity (or, as it is termed by the French savants, "density"),
it may be as well to state that astronomers have been enabled, by taking the density of the earth and by
astronomical observations, to calculate the gravity of the planets belonging to our solar system; and it is
interesting to observe that the density of the planet Venus is the only one approaching the gravity of the earth:—

The Earth 1.000
The Sun .254
The Moon .742
Mercury 2.583
Venus 1.037
Mars .650
Jupiter .258
Saturn .104
Herschel .220

CHAPTER VI.
ATTRACTION OF COHESION.

In previous chapters one kind of attraction—viz., that of gravitation, has been discussed and illustrated in a
popular manner, and pursuing the examination of the invisible, active, and real forces of nature, the attraction of
cohesion will next engage our attention. There is a peculiar satisfaction in pursuing such investigations, because
every step is attended by a reasonable proof; there is no ghostly mystery in philosophic studies; the mind is not
suddenly startled at one moment with that which seems more than natural; it is not carried away in an ecstasy of
wonder and awe, as in the so-called spirit-rapping experiments, to be again rudely brought back to the material
by the disclosure of trickeries of the most ludicrous kind, such as those lately exposed by M. Jobert de Lamballe,
at the Academy of Sciences at Paris. This gentleman has unmasked the effrontery of the spirit-rappers by merely
stripping the stocking from the heel of a young girl of fourteen. M. Velpeau declares that the rapping is produced
by the muscles of the heel and knee acting in concert, and quotes the case of a lady once celebrated as a medium,
who has the power of producing the most curious and interesting music with the tendons of the thigh. This music
is said to be loud enough to be heard from one end of a long room to the other, and has often played a
conspicuous part in the revelations made by the medium. M. Jules Clocquet also explained the method by which
the famous girl pendulum had so long abused the credulity of the Paris public. This girl, whose self-styled
faculty is that of striking the hour at any time of the day or night, was attended at the Hospital St. Louis by M.
Clocquet, who states that the vibrations in this case were produced by a rotatory motion in the lumbar regions of
the vertebral column. The sound of these (à la rattlesnake) was so powerful, that they might be distinctly heard
at a distance of twenty-five feet.
In studying the powers of nature, which the most sceptical mind allows must exist, there is an abundant field for
experiment without attempting the exploits of Macbeth's witches, or the fanciful powers of Manfred; and,
returning to the theme of our present chapter, it may be asked, how is cohesion defined? and the answer may be
given, by directing attention to the three physical conditions of water, which assumes the form of ice, water, or
steam.
In the Polar regions, and also in the Alpine and other mountains where glaciers exist, there the traveller speaks
of ice twenty, thirty, forty, nay, three hundred feet in thickness. Here the withdrawal of a certain quantity of heat
from the water evidently allows a new force to come into full play. We may call it what we like; but cohesion,
from the Latin cum, together, and hæreo, I stick or cleave, appears to be the best and most rational term for this
power which tends to make the atoms or particles of the same kind of matter move towards each other, and to
prevent them being separated or moved asunder. That it is not merely hypothetical is shown by the following
experiments.
If two pieces of lead are cast, and the ends nicely scraped, taking care not to touch the surfaces with the fingers,
they may by simple pressure be made to cohere, and in that state of attraction may be lifted from the table by the
ring which is usually inserted for convenience in the upper piece of lead; they may be hung for some time from a
proper support, and the lower bit of lead will not break away from the upper one; they may even be suspended,
as demonstrated by Morveau, in the vacuum of an air-pump, to show that the cohesion is not mistaken for the
pressure of the atmosphere, and no separation occurs. And when the union is broken by physical force, it is
surprising to notice the limited number of points, like pin points, where the cohesion has occurred; whilst the
weight of the lump of lead upheld against the force of gravitation reminds one forcibly of the attraction of a
mass of soft iron by a powerful magnet, and leads the philosophic inquirer to speculate on the principle of
cohesion being only some masked form of magnetic or electrical attraction. (Fig. 75.)
A fine example of the same force is shown in the use of a pair of flat iron surfaces, planed by the celebrated
Whitworth, of Manchester. These surfaces are so true, that when placed upon each other, the upper one will
freely rotate when pushed round, in consequence of the thin film of air remaining between the surfaces, which
acts like a cushion, and prevents the metallic cohesion. When, however, the upper plate is slid over the lower one

gradually, so as to exclude the air, then the two may be lifted together, because
cohesion has taken place. (Fig. 76.)

Fig. 75.
a a. Two pieces of lead, scraped

clean at the surfaces b b. c.
Stand, supporting the two pieces
of lead attached to each other by
cohesion.

Fig. 76.
a. Whitworth's planes, with film of air between them. b. Film of air
excluded when cohesion occurs.

A glass vessel is a good example of cohesion. The materials of which it is composed have been soft and liquid
when melted in the fire, and on the removal of the excess of heat it has become hard and solid, in consequence
of the attractive force of cohesion binding the particles together; in the absence of such a power, of course, the
material would fall into the condition of dust, and a mere shapeless heap of silicates of potash and lead would
indicate the place where the moulded and coherent glass would otherwise stand.

A lump of lead, six inches long by four broad, and half an inch thick, may be supported by dexterously taking
off a thick shaving with a proper plane, and after pressing an inch or more of the strip on the planed surface of
the large lump of lead, the cohesion is so powerful that the latter may be lifted from the table by the strip of
metal.
The bullets projected from Perkins' steam-gun, at the rate of three hundred per minute, are thrown with such
violence, that, when received on a thick plate of lead backed up with sheet iron, a cold welding takes place
between the two surfaces of metal in the most perfect manner, just as two soft pieces of the metal potassium may
be squeezed and welded together. The surfaces of an apple torn asunder will not readily cohere, but if cut with a
sharp knife, cohesion easily occurs; so with a wound produced by a jagged surface, it is difficult to make the
parts heal, whereas some of the most desperate sabre-cuts have been healed, the cohesion of the surfaces of cut
flesh being very rapid; hence, if the top of a finger is cut off, it may be replaced, and will grow, in consequence
of the natural cohesion of the parts.
The art of plating copper with silver, which is afterwards gilt, and then drawn out into flattened wire for the
manufacture of gold lace and epaulets, usually termed bullion, is another example of the wonderful cohesion of
the particles of gold, of which a single grain may be extended over the finest plate wire measuring 345 feet in
length.
The process of making wax candles is a good illustration of the attraction of cohesion; they are not generally
cast in moulds, as most persons suppose, but are made by the successive applications of melted wax around the
central plaited wick. Other examples of cohesion are shown by icicles, and also stalagmites; which latter are
produced by the gradual dropping of water containing chalk (carbonate of lime) held in solution by the excess of
carbonic acid gas; the solvent gradually evaporates, and leaves a series of calcareous films, and these cohere in
succession, producing the most fantastic forms, as shown in various remarkable caverns, and especially in the
cave of Arta, in the island of Majorca.
In metallic substances the cohesion of the particles assumes an important bearing in the question of relative
toughness and power of resisting a strain; hence the term cohesion is modified into that of the property of
"tenacity."
The tenacity of the different metals is determined by ascertaining the weight required to break wires of the same
length and gauge. Iron appears to possess the property of tenacity in the greatest, and lead in the least degree.
(Fig. 77.)

Fig. 77.
b. Pan supported by leaden wire broken by a weight which the iron wire at a easily supports.

The tenacity of iron is taken advantage of in the most scientific manner by the great engineers who have
constructed the Britannia Tube, and that eighth wonder of the world, the Leviathan, or Great Eastern steam-ship.
In both of these sublime embodiments of the genius and industrial skill of Great Britain the advantage of the
cellular principle is fully recognised. The magnitude of this colossal ship is better realized when it is
remembered that the Great Eastern is six times the size of the Duke of Wellington line-of-battle ship, that her
length is more than three times that of the height of the Monument, while in breadth it is equal to the width of
Pall Mall, and that a promenade round the deck will afford a walk of more than a quarter of a mile. Up to the
water-mark the hull is constructed with an inner and outer shell, two feet ten inches apart, each of three-quarter-
inch plate; and between them, at intervals of six feet, run horizontal webs of iron plates, which convert the whole
into a series of continuous cells or iron boxes. (Fig. 78.)

Fig. 78.
Transverse section of Great Eastern, showing the cellular construction from keel to water-line, a a.

This double ship is useful in various ways; in the first place, the danger arising from collision is diminished, as it
is supposed that the outer web only would be broken through or damaged; so that the water would not then rush
into the steam-ship, but merely fill the space between the shells. In the second place, if there should be any
difficulty in procuring ballast, the space can be filled with 2500 tons of water, or again pumped out, according to
the requirements of the vessel. The strength of a continued cellular construction can be easily imagined, and may
be well illustrated by a thin sheet of common tin plate. If the ends be rested on blocks of wood, so as to lap over
the wood about one inch, they are easily displaced, and the mimic bridge broken down from its supports by the
addition to the centre of a few ounce weights; whilst the same tin plate rolled up in the figure of a tube, and
again rested on the same blocks, will now support many pounds weight without bending or breaking down. (Fig.
79.)

Fig. 79.
a. Flat tin plate, breaking down with a few ounce weights. b. Same tin plate rolled up supports a very heavy weight.

The deck of the ship is double or cellular, after the plan of Stephenson in the Britannia Tubular Bridge, and is
692 feet in length. The tonnage register is 18,200 tons, and 22,500 tons builder's measure; the hull of the Great
Eastern is considered to be of such enormous tenacity, that, if it were supported by massive blocks of stone six
feet square, placed at each end, at stem and stern, it would not deflect, curve, or bend down in the middle more
than six inches even with all her machinery, coals, cargo, and living freight.
In adducing remarkable instances of the adhesive power and tenacity of inorganic matter, it may not be
altogether out of place to allude to the strength and force of living matter, or muscular power. It is stated that Dr.
George B. Winship, of Roxbury in America, a young physician, twenty-five years old, and weighing 143
pounds, is the strongest man alive; in fact, quite the Samson of the nineteenth century. He can raise a barrel of
flour from the floor to his shoulders; can raise himself with either little finger till his chin is half a foot above it;
can raise 200 pounds with either little finger; can put up a church bell of 141 pounds; can lift with his hands 926
pounds dead weight without the aid of straps or belts of any kind. As compared with Topham, the Cornish strong
man, who could raise 800 pounds, or the Belgic one, his power is greater; and as the use of straps and belts
increases the power of lifting by about four times, it is stated that Winship could lift at least 2500 pounds weight.
With these illustrations of cohesion we may return again to the abstract consideration
of this power with reference to water, in which we have noticed that the antagonist to
this kind of attraction is the force or power termed caloric or heat. The latter
influence removes the frozen bands of winter and converts the ice to the next
condition, water. In this state cohesion is almost concealed, although there is just a
slight excess to hold even the particles of water in a state of unity, and this fact is
beautifully illustrated by the formation of the brilliant diamond drops of dew on the
surfaces of various leaves, as also in the force and power exercised by great volumes
of water, which exert their mighty strength in the shape of breaker-waves, dashing
against rocks and lighthouses, and making them tremble to their very base by the
violence of the shock; here there must be some unity of particles, or the collective
strength could not be exerted, it would be like throwing a handful of sand against a
window—a certain amount of noise is produced, but the glass is not fractured; whilst
the same sand united by any glutinous material, would break its way through, and
soon fracture the brittle glass. It is so usual to see the particles of water easily
separated, that it becomes difficult to recognise the presence of cohesion; but this
bond of union is well illustrated in the experiment of the water hammer. The little
instrument is generally made of a glass tube with a bulb at one end; in this bulb the
water which it contains is boiled, and as the steam issues from the other extremity,
drawn out to a capillary tube, the opening is closed by fusion with the heat of a
blowpipe flame. As the water cools the steam condenses, and a vacuum, so far as air
is concerned, is produced; if now the tube is suddenly inverted, the whole of the
water falls en masse, collectively, and striking against the bottom of the tube,
produces a metallic ring, just as if a piece of wood or metal were contained within
the tube. If the end to which the water falls is not well cushioned by the palm of the
hand, the water hammers itself through and breaks away that part of the glass tube.
Hence it is better to construct the water hammer of copper tube, about three-quarters
of an inch in diameter and three feet long; at one end a female screw-piece is
inserted, into which a stop-cock is fitted; when the tube is filled to the height of Fig. 80.
about six inches with water, and shaken, the air divides the descending volume of
water, and the ordinary splashing sound is heard; there is no unity or cohesion of the a. Ordinary glass water hammer.
parts; if, however, the end of the copper tube is thrust into a fire and the water boiled b. Copper tube ditto, showing
so that steam issues from the cock, which is then closed, and the tube removed and exhausting syringe at d, the
cooled, a smart blow is given, and distinctly heard when the copper tube is rapidly height of the water at b, and the
inverted or shaken so as to cause the water to rise and fall. The experiment may be end to be placed in the fire at c.
rendered still more instructive by turning the cock and admitting the air, which
rushes in with a whizzing sound, and on shaking the tube the metallic ring is no
longer heard, but it may be again restored by attaching a small air syringe or hand pump, and removing the air
by exhaustion. (Fig. 80.)

In the fluid condition water still possesses a surplus of cohesion over the antagonistic force of heat; when,
however, the latter is applied in excess, then the quasi-struggle terminates; the heat overpowers the cohesive
attraction, and converts the water into the most willing slave which has ever lent itself to the caprices of man—
viz., into steam—glorious, useful steam: and now the other end of the chain is reached, where heat triumphs;
whilst in solids, such as ice, cohesion is the conqueror, and the intermediate link is displayed in the fluid state of
water. If any fact could give an idea of the gigantic size of the Great Eastern, it is the force of the steam which
will be employed to move it at the rate of about eighteen miles per hour with a power estimated at the nominal
rate of 2600 horses, but absolutely of at least 12,000 horses. This steam power, coupled with the fact that she has
been enormously strengthened in her sharp, powerful bows, by laying down three complete iron decks forward,
extending from the bows backward for 120 feet, will demonstrate that in case of war the Great Eastern may
prove to be a powerful auxiliary to the Government. These decks will be occupied by the crew of 300 or 400
men, and with this large increase of strength forward, the Great Eastern, steaming full power, could overtake
and cut in two the largest wooden line-of-battle ship that ever floated. Should war unhappily spread to peaceful
England, and the enormous power of this vessel be realized, her name would not inappropriately be changed
from the Great Eastern to the Great Terror of the ocean. The Times very properly inquires, "What fleet could
stand in the way of such a mass, weighing some 30,000 tons, and driven through the water by 12,000 horse-
power, at the rate of twenty-two or twenty-three miles per hour. To produce the steam, 250 tons of coal per diem
will be required, and great will be the honourable pride of the projectors when they see her fairly afloat, and
gliding through the ocean to the Far West."
A good and striking experiment, displaying the change from the liquid to the vapour state, is shown by tying a
piece of sheet caoutchouc over a tin vessel containing an ounce or two of water. When this boils, the india-
rubber is distended, and breaks with a loud noise; or in another illustration, by pouring some ether through a
funnel carefully into a flask placed in a ring stand. If flame is applied to the orifice, no vapour issues that will
ignite, provided the neck of the flask has not been wetted with the ether. When, however, the heat of a spirit-
lamp is applied, the ether soon boils, and now on the application of a lighted taper, a flame some feet in length is
produced, which is regulated by the spirit-lamp below, and when this is removed, the length of the flame
diminishes immediately, and is totally extinguished if the bottom of the flask is plunged into cold water; the
withdrawal of the heat restores the power of cohesion. Another illustration of the vast power of steam will be
shortly displayed in the Steam Ram; and, "Supposing," says the Times, "the new steam ram to prove a successful
design, the finest specimens of modern men-of-war will be reduced by comparison to the helplessness of cock
boats. Conceive a monstrous fabric floating in mid-channel, fire proof and ball proof, capable of hurling
broadsides of 100 shot to a distance of six miles; or of clapping on steam at pleasure and running down
everything on the surface of the sea with a momentum utterly irresistible.
"This terrible engine of destruction is expected to be itself indestructible. We are told that she may be riddled
with shot (supposing any shot could pierce her sides), that she may have her stem and her stern cut to pieces, and
be reduced apparently to a shapeless wreck, without losing her buoyancy or power. Supposing that she relies
upon the shock of her impact instead of fighting her guns, it is calculated that she would sink a line-of-battle
ship in three minutes, so that a squadron as large as our whole fleet now in commission would be destroyed in
about one hour and a quarter."

CHAPTER VII.
ADHESIVE ATTRACTION.

The term cohesion must not be confounded with that of adhesion, which refers to the clinging to or attraction of
bodies of a dissimilar kind. The late Professor Daniell defines cohesion to be an attraction of homogeneous
(ὁμος, like, and γενος, kind) or similar particles; adhesion to be an attraction subsisting between particles of a
heterogeneous, ετερος, different, and γενος, kind.
There are numerous illustrations of adhesion, such as mending china, and the use of glue, or paste, in uniting
different surfaces, or mortar, in building with bricks; it is also well shown at the lecture table by means of a pair
of scales, one scale-pan of which being well cleaned with alkali at the bottom, may then be rested on the surface
of water contained in a plate; the adhesion between the water and the metal is so perfect, that many grain
weights may be placed in the other pan before the adhesion is broken; and after breakage, if the pan be again
placed on the water, and a few grains removed from the other, so as to adjust the two pans, and make them
nearly equal, a drop of oil of turpentine being added, instantly spreads itself over the water, and breaking the
adhesion between the latter and the metal, the scale-pan is immediately and again broken away, as the adhesion
between the turpentine and the metal is not so great as that of water and metal. The adhesion of air and water is
well displayed in an apparatus recommended for ventilating mines, in which a constant descending stream of
water carries with it a quantity of air, which being disengaged, is then forced out of a proper orifice. The same
kind of adhesion between air and water is displayed in the ancient Spanish Catalan forge, where the blast is
supplied to the iron furnace on a similar principle, only, a natural cascade is taken advantage of instead of an
artificial fall of water through a pipe.
The adhesion of air and water becomes of some value when a river flows through a large and crowded city,
because the water in its passage to and fro, must necessarily drag with it, a continuous column of air, and assist
in maintaining that constant agitation of the air which is desirable as a preventive to any accumulation of
noxious air charged with fœtid odours, arising from mud banks or from other causes. The fact of adhesion,
existing between water and air, is readily shown, by resting one end of a long glass tube, of at least one inch
diameter, on a block of wood one foot high. If water is allowed to flow down the tube, so as to leave a sufficient
space of air above it, the adhesion between the two ancient elements becomes apparent, directly a little smoke is
produced, near the top end of the glass tube resting on the block of wood. The smoke, which has a greater
tendency to rise than to fall, is dragged down the glass tube, and accompanies the water as it flows from the
higher to the lower level. The same truth is also illustrated in horizontal troughs or tubes through which water is
caused to flow.
The adhesion between air and glass is so great, that it is absolutely necessary to boil the mercury in the tubes of
the best barometers; and if this is not carefully attended to, the adhering air between the glass and mercury
gradually ascends to, and destroys, the Torricellian vacuum at the top of the barometer tube. Even after the
mercury is boiled, the air will creep up in course of years; and in order to prevent its passage between the glass
and quicksilver, it has been recommended, that a platinum ring should be welded on to the end of the glass tube,
because mercury has the power of wetting or enfilming the metal platinum, and the two being in close contact,
would, as it were, shut the only door by which the air could enter the barometer tube.

Fig. 81.
Model of the apparatus for drawing down air. a, cistern of water, supplied by ball-cock, and kept at one level, so that the water
just runs down the sides of the tube, and draws down the air in the centre, b c. The vessel to which the air and water are
conveyed by a gutta-percha tube, t. There is another ball-cock to permit the waste water to run away when it reaches a certain
level; the end of the pipe always dips some inches into this water, whilst the air escapes from the jet, d.

CHAPTER VIII.
CAPILLARY ATTRACTION.

This kind of attraction is termed capillary, in consequence of tubes, of a calibre, or bore, as fine as hair,
attracting and retaining fluids.
If water is poured into a glass, the surface is not level, but cupped at the edges, where the solid glass exerts its
adhesive attraction for the liquid, and draws it from the level. If the glass be reduced to a very narrow tube,
having a hair-like bore, the attraction is so great that the water is retained in the tube, contrary to the force of
gravitation. Two pieces of flat glass placed close together, and then opened like a book, draw up water between
them, on the same principle. A mass of salt put on a plate containing a little water coloured with indigo displays
this kind of attraction most perfectly, and the water is quickly drawn up, as shown by the blue colour on the salt.
A little solution of the ammonio-sulphate of copper imparts a finer and more distinct blue colour to the salt. A
piece of dry Honduras mahogany one inch square, placed in a saucer containing a little turpentine, is soon found
to be wet with the oil at the top, which may then be set on fire.
Almost every kind of wood possesses capillary tubes, and will float, on account of these minute vessels being
filled with air; if, however, the air is withdrawn, then the wood sinks, and by boiling a ball made of beech wood
in water, and then placing it under the vacuum of an air pump in other cold water, it becomes so saturated with
water that it will no longer float. A remarkable instance of the same kind is mentioned by Scoresby, in which a
boat was pulled down by a whale to a great depth in the ocean, and after coming to the surface it was found that
the wood would neither swim nor burn, the capillary pores being entirely filled with salt water.
A piece of ebony sinks in water on account of its density, closeness, and freedom from air. A gauge made of a
piece of oak, with a hole bored in it of one inch diameter, accurately receives a dry plug of willow wood which
will not enter the orifice after it is wetted. Millstones are split by inserting wedges of dry hard wood, which are
afterwards wetted and swelled, and burst the stone asunder. One of the most curious instances of capillary
attraction is shown in the currying of leather, a process which is intended to impart a softness and suppleness to
the skin, in order that it may be rendered fit for the manufacture of boots, harness, machine bands, &c. The
object of the currier is to fill the pores of the leather with oil, and as this cannot be done by merely smearing the
surface, he prepares the way for the oil by wetting the leather thoroughly with water, and whilst the skin is
damp, oil is rubbed on, and it is then exposed to the air; the water evaporates at ordinary temperatures, but oil
does not; the consequence is that the pores of the leather give up the water, which disappears in evaporation, and
the oil by capillary attraction is then drawn into the body of the leather, the oil in fact takes the place vacated by
the water, and renders the material very supple, and to a considerable extent waterproof. In paper making, the
pores of this material, unless filled up or sized, cause the ink to blot or spread by capillary attraction. The
porosity of soils is one of the great desideratums of the skilful agriculturist, and drainage is intended to remove
the excess of water which would fill the pores of the earth, to the exclusion of the more valuable dews and rains
conveying nutritious matter derived from manures and the atmosphere.
A cane is an assemblage of small tubes, and if a piece of about six inches in length (cut off, of course, from the
joints) be placed in a bottle of turpentine, the oil is drawn up and may be burnt at the top; it is on this principle
that indestructible wicks of asbestos, and wire gauze rolled round a centre core, are used in spirit lamps. Oil,
wax, and tallow, all rise by capillary attraction in the wicks to the flame, where they are boiled, converted into
gas, and burnt.
The capillary attraction of skeins of cotton for water was known and appreciated by the old alchemists; and
Geber, one of the most ancient of these pioneers of science, and who lived about the seventh century, describes a
filter by which the liquid is separated from the solid. This experiment is well displayed by putting a solution of
acetate of lead into a glass, which is placed on the highest block of a series of three, arranged as steps. Into this
glass is placed the short end of a skein of lamp cotton, previously wetted with distilled water; the long end dips
into another glass below, containing dilute sulphuric acid, and as the solution of lead passes into it, a solid white

precipitate of sulphate of lead is formed; then another skein of wetted
cotton is placed in this glass, the long end of which passes into the last
glass, so that the clear liquid is separated and the solid left behind. (Fig.
82.)
In this filter the lamp cotton acts as a syphon
through the capillary pores which it forms. On the
same principle, a prawn may be washed in the most
elegant manner (as first shown by the late Duke of
Sussex), by placing the tail, after pulling off the fan
part, in a tumbler of water, and allowing the head to
hang over, when the water is drawn up by capillary
attraction, and continues to run through the head.
(Fig. 83.)
The threads of which linen, cotton, and woollen
cloths are made are small cords, and the shrinkage
of such textile fabrics, is well known and usually
inquired about, when a purchase is made; here
again capillary attraction is exerted, and the fabric
contracts in the two directions of the warp and
Fig. 82. woof threads; thus, twenty-seven yards of common
Geber's filter. a. The solution of acetate of lead. Irish linen will permanently shrink to about twenty-
b. The dilute sulphuric acid. c. The clear liquid,
six yards in cold water. In these cases the water is
separated from the sulphate of lead in b. attracted into the fibres of the textile material, and
causing them to swell, must necessarily shorten
their length, just as a dry rope strained between two
walls for the purpose of supporting clothes, has been known to draw the hooks after being
suddenly wetted and shortened by a shower of rain.
In order to tighten a bandage, it is only necessary to wind the dry linen round the limbs as
close as possible, and then wet it with water, when the necessary shrinkage takes place.
Fig. 83.
If a piece of dry cotton cloth is tied over one end of a lamp glass, the other may be thrust
into, or removed from the basin of water very easily, but when the cotton is wetted, the Prawn syphon.
fibres contract and prevent air from entering, so that the glass retains water just as if it were
an ordinary gas jar closed with a glass stopper.
A Spanish proverb, expressing contempt, says, "go to the well with a sieve,"
but even this seeming impossibility is surmounted by using a cylinder of wire
gauze, which may be filled with water, and by means of the capillary attraction
between the meshes of the copper-wire gauze and the water, the whole is
retained, and may be carefully lifted from a basin of water; the experiment
only succeeds when the air is completely driven out of the interstices of the
gauze, and the little cylinder completely filled with water; this may be done by
repeatedly sinking and drawing out the cylinder, or still more effectually, by
first wetting it with alcohol and then dipping the cylinder in water. Fig. 84.
A balloon, made of cotton cloth, cannot be inflated by means of a pair of a. Basin of water. b. Cylinder of wire
bellows, but if the balloon is wetted with water, then it may be swelled out gauze closed at both ends with gauze.
with air just as if it had been made of some air-tight material; hence the When full of water it may be lifted from
principle of varnishing silk or filling the pores with boiled oil, when it is the basin by the handle, c.
required in the manufacture of balloons.
Biscuit ware, porous tubes for voltaic batteries, alcarrazas, or water coolers,
are all examples of the same principle.

Whilst speaking most favourably of the benevolent labours of many gentlemen (beginning with Mr. Gurney)
who have erected "Drinking Fountains" in London's dusty atmosphere and crowded streets, it must not be
forgotten that pious Mohammedans have, in bygone times, already set us the example in this respect; and in the
palmy days of many of the Moorish cities, the thirsty citizen could always be refreshed by a draught of cool
water from the porous bottles provided and endowed by charitable Mussulmans, and placed in the public streets.

Fig 85.
Moorish niche and porous earthenware bottle, containing water.

CHAPTER IX.
CRYSTALLIZATION.

Fig. 86.
Crystals of snow.
It has been already stated that the force of cohesion binds the similar particles of substances together, whether
they be amorphous or shapeless, crystalline or of a regular symmetrical and mathematical figure. The term
crystal was originally applied by the ancients to silica in the form of what is usually termed rock crystal, or
Brazilian pebble; and they supposed it to be water which had been solidified by a remarkable intensity of cold,
and could not be thawed by any ordinary or summer heat. Indeed, this idea of the ancients has been embodied
(to a certain extent) in the shape of artificial ice made by crystallizing large quantities of sulphate of soda, which
was made as flat as possible, and upon which skaters were invited to describe the figure of eight, at the usual
admittance fee, representing twelve pence. A crystal is now defined to be an inorganic body, which, by the
operation of affinity, has assumed the form of a regular solid terminated by a certain number of planes or smooth
surfaces.
Thousands of minerals are discovered in the crystallized state—such as cubes of iron pyrites (sulphuret of iron)
and of fluor spar (fluoride of calcium), whilst numerous saline bodies called salts are sold only in the form of
crystals. Of these salts we have excellent examples in Epsom salts (sulphate of magnesia), nitre (nitrate of
potash), alum (sulphate of alumina), and potash; the term salt being applied specially to all substances composed
of an acid and a base, as also to other combinations of elements which may or may not take a crystalline form.
Thus, nitre is composed of nitric acid and potash; the first, even when much diluted, rapidly changes paper,
dipped in tincture of litmus and stained blue, to a red colour, whilst potash shows its alkaline nature, by changing
paper, stained yellow with tincture of turmeric, to a reddish-brown. The latter paper is restored to its original
yellow by dipping it into the dilute nitric acid, whilst the litmus paper regains its delicate blue colour by being
passed into the alkaline solution. An acid and an alkali combine and form a neutral salt, such as nitre, which has
no action whatever on litmus or turmeric; whilst the element iodine, which is not an acid, unites with the
metallic element potassium, and therefore not an alkali, and forms a salt that crystallizes in cubes called iodide
of potassium. Again, cane sugar, which is composed of charcoal, oxygen, and hydrogen, crystallizes in hard
transparent four-sided and irregular six-sided prisms, but is not called a salt. Silica or sand is found crystallized
most perfectly in nature in six-sided pyramids, but is not a salt; it is an acid termed silicic-acid. Sand has no acid
taste, because it is insoluble in water, but when melted in a crucible with an alkali, such as potash, it forms a salt

called silicate of potash. Magnesia, from being insoluble, or nearly so, in water, is all but tasteless, and has
barely any alkaline reaction, yet it is a very strong alkaline base; 20.7 parts of it neutralize as much sulphuric
acid as 47 of potash. A salt is not always a crystallizable substance, and vice versa. The progress of our chemical
knowledge has therefore demanded a wider extension and application of the term salt, and it is not now confined
merely to a combination of an acid and an alkali, but is conferred even on compounds consisting only of sulphur
and a metal, which are termed sulphur salts.
So also in combinations of chlorine, iodine, bromine, and fluorine, with metallic bodies, neither of which are
acid or alkaline, the term haloid salts has been applied by Berzelius, from the Greek ( αλς, sea salt, and ειδος
form), because they are analogous in constitution to sea salt; and the mention of sea salt again reminds us of the
wide signification of the term salt, originally confined to this substance, but now extended into four great orders,
as defined by Turner:—
Order I. The oxy-salts.—This order includes no salt the acid or base of which is not an oxidised body (ex.,
nitrate of potash).
Order II. The hydro-salts.—This order includes no salt the acid or base of which does not contain hydrogen (ex.,
chloride of ammonium).
Order III. The sulphur salts.—This order includes no salt the electro-positive or negative ingredient of which is
not a sulphuret (ex., hydrosulphuret of potassium).
Order IV. The haloid salts.—This order includes no salt the electro-positive or negative ingredient of which is
not haloidal. (Exs., iodide of potassium and sea salt). To fix the idea of salt still better in the youthful mind, it
should be remembered that alabaster, of which works of art are constructed, or marble, or lime-stone, or chalk,
are all salts, because they consist of an acid and a base.
In order to cause a substance to crystallize it is first necessary to endow the particles with freedom of motion.
There are many methods of doing this chemically or by the application of heat, but we cannot by any mechanical
process of concentration, compression, or division, persuade a substance to crystallize, unless perhaps we except
that remarkable change in wrought or fibrous iron into crystalline or brittle iron, by constant vibration, as in the
axles of a carriage, or by attaching a piece of fibrous iron to a tilt hammer.
If we powder some alum crystals they will not again assume their crystalline form; if brought in contact there is
no freedom of motion. It is like placing some globules of mercury on a plate. They have no power to create
motion; their inertia keeps them separated by certain distances, and they do not coalesce; but incline the plate,
give them motion, and bring them in contact, they soon unite and form one globule. The particles of alum are not
in close contact, and they have no freedom of motion unless they are dissolved in water, when they become
invisible; the water by its chemical power destroys the mechanical aggregation of the solid alum far beyond any
operation of levigation. The solid alum has become liquid, like water; the particles are now free to move without
let or hindrance from friction. A solution, (from the Latin solvo, to loosen) is obtained. The alum must indeed be
reduced to minute particles, as they are alike invisible to the eye whether assisted by the microscope or not. No
repose will cause the alum to separate; the solvent power of the water opposes gravitation; every part of the
solution is equally impregnated with alum, and the particles are diffused at equal distances through the water;
the heavy alum is actually drawn up against gravity by the water.
How, then, is the alum to be brought back again to the solid state? The answer is simple enough. By evaporating
away the excess of water, either by the application of heat or by long exposure to the atmosphere in a very
shallow vessel, the minute atoms of the alum are brought closer together, and crystallization takes place. The
assumption of the solid state is indicated by the formation of a thin film (called a pellicle) of crystals, and is
further and still more satisfactorily proved by taking out a drop of the solution and placing it on a bit of glass,
which rapidly becomes filled with crystals if the evaporation has been carried sufficiently far (Fig. 87).
After evaporating away sufficient water, the dish is placed on one side and allowed to cool, when crystals of the
utmost regularity of form are produced, and, denoted by a geometrical term, are called octohedral or eight-sided
crystals, when in the utmost state of perfection (Fig. 88).

The science of crystallography is
too elaborate to be discussed at
length in a work of this kind; the
various terms connected with
crystals will therefore only be
explained, and experiments
given in illustration of the
formation of various crystals.
When the apices—i.e., the tips
or points of crystals—are cut
off, they are said to be truncated;
and the same change occurs on
the edges of numerous crystals.
Fig. 88.
If some of the salt called
chloride of calcium in the dry
Fig. 87. and amorphous state is exposed to the air, it soon absorbs water, or what
is termed deliquesces: the same thing occurs with the crystals of
r r. Ring-stand. s s. Spirit-lamps. a. Flask
carbonate of potash, and if four ounces are weighed out in an
containing boiling solution of alum.—Solution. b.
evaporating dish, and then exposed for about half an hour to the air, a
Funnel, with a bit of lamp-cotton stuffed in the
very perceptible increase in weight is observed by the assistance of the
bottom.—Filtration. c. Evaporating dish.—
scales and grain weights. Deliquescence is a term from the Latin
Evaporation. d. Drop on glass.—Crystallization.
deliqueo, to melt, and is in fact a gradual melting, caused by the
absorption of water from the atmosphere. The reverse of this is
illustrated with various crystals, such as Glauber's salt (sulphate of
soda), or common washing soda (carbonate of soda); if a fine clear crystal is taken out of the solution, called the
mother liquor, in which it has been crystallized, wiped dry, and placed under a glass shade, this salt may remain
for a long period without change, but if it receive one scratch from a pin, the door is opened apparently for the
escape of the water which it contains, chemically united with the salt, and called water of crystallization; the
white crystal gradually swells out, the little quasi sore from the pin-scratch spreads over the whole, which
becomes opaque, and crumbling down falls into a shapeless mass of white dust; this change is called
efflorescence, from effloresco, to blow as a flower—caused by the abstraction from them of chemically-
combined water by the atmosphere. With reference to the preservation of crystals, Professor Griffiths
recommends them to be oiled and wiped, and placed under a glass shade, if of a deliquescent nature; or if
efflorescent, they are perfectly preserved by placing them under a glass shade with a little water in a cup to keep
the air charged with moisture and prevent any drying up of the crystal.
Deliquescent crystals may be preserved by placing them, when dry, in naphtha, or any liquor in which they are
perfectly insoluble. Some salts, like Glauber's salts, contain so much water of crystallization that when subjected
to heat they melt and dissolve in it, and this liquefaction of the solid crystal is called "watery fusion." Other salts,
such as bay salt, chlorate of potash, &c., when heated, fly to pieces, with a sharp crackling noise, which is due
sometimes, to the unequal expansion of the crystalline surface, or the sudden conversion of the water (retained
in the crystal by capillary attraction) into steam; thus nitre behaves in this manner, and frequently retains water
in capillary fissures, although it is an anhydrous salt, or salt perfectly free from combined water. The crackling
sound is called decrepitation, and is well illustrated by throwing a handful of bay salt on a clear fire; but this
property is destroyed by powdering the crystals.
Many substances when melted and slowly cooled concrete into the most perfect crystals; in these cases heat
alone, the antagonist to cohesion, is the solvent power. Thus, if bismuth be melted in a crucible, and when
cooling, and just as the pellicle (from pellis, a skin or crust) is forming on the surface, if two small holes are
instantly made by a rod of iron and the liquid metal poured out from the inside (one of the holes being the
entrance for the air, the other the exit for the metal); on carefully breaking the crucible, the bismuth is found to
be crystallized in the most lovely cubes. Sulphur, again, may be crystallized in prismatic crystals by pursuing a
similar plan; and the great blocks of spermaceti exhibited by wax chandlers in their windows, are crystallized in
the interior and prepared on the same principle.

There are other modes of conferring the crystalline state upon substances—viz., by elevating them into a state of
vapour by the process called sublimation (from sublimis, high or exalted), the lifting up and condensation of the
vapour in the upper part of a vessel; a process perfectly distinct from that of distillation, which means to separate
drop by drop. Both of these processes are very ancient, and were invented by the Arabian alchemists long
antecedent to the seventh century. Examples of sublimation are shown by heating iodine, and especially benzoic
acid; with the latter, a very elegant imitation of snow is produced, by receiving the vapour, on some sprigs of
holly or other evergreen, or imitation paper snowdrops and crocuses, placed in a tasteful manner under a glass
vessel. The benzoic acid should first be sublimed over the sprigs or artificial flowers in a gas jar, which may be
removed when the whole is cold, and a clear glass shade substituted for it. (Fig. 89.)
All electro deposits on metals are more or less crystalline; and copper or silver may
be deposited in a crystalline form by placing a scraped stick of phosphorus in a
solution of sulphate of copper or of nitrate of silver. The phosphorus takes away the
oxygen from the metal, or deoxidizes the solution, and the copper or silver reappears
in the metallic form. The surface of the phosphorus must not be scraped in the air,
but under water, when the operation is perfectly safe.
A singular and almost instantaneous crystallization can be produced by saturating
boiling water with Glauber's salt, of which one ounce and a half of water will usually
dissolve about two ounces; having done this, pour the solution, whilst boiling hot,
into clean oil flasks, or vials of any kind, previously warmed in the oven, and
immediately cork them, or tie strips of wetted bladder, over the orifices of the flasks
or vials, or pour into the neck a small quantity of olive oil, or close the neck with a
cork through which a thermometer tube has been passed. When cold, no
crystallization occurs until atmospheric air is admitted; and it was formerly believed
that the pressure of the air effected this object, until some one thought of the oil, and
now the theory is modified, and crystallization is supposed to occur in consequence
of the water dissolving some air which causes the deposit of a minute crystal, and
this being the turning point, the whole becomes solid. However the fact may be
explained, it is certain that when the liquid refuses to crystallize on the admission of
air, the solidification occurs directly a minute crystal of sulphate of soda, or
Fig. 89. Glauber's salt, is dropped into the vessel.
a. Gas-jar, with stopper open at
When the crystallization is accomplished, the whole mass is usually so completely
first, to be shut when the lamp is
solidified, that on inverting the vessel, not a drop of liquid falls out.
withdrawn. b. Wooden stand,
with hole to carry the cup c, It may be observed that the same mass of salt will answer any number of times the
containing the benzoic acid, same purpose. All that is necessary to be done, is to place the vial or flask, in a
heated below by the spirit-lamp, saucepan of warm water, and gradually raise it to the boiling point till the salt is
s. f. Flowers or sprigs arranged completely liquefied, when the vessel must be corked and secured from the air as
on pieces of rock or mineral. before. When the solidification is produced much heat is generated, which is
rendered apparent by means of a thermometer, or by the insertion of a copper wire
into the pasty mass of crystal in the flask, and then touching an extremely thin
shaving or cutting of phosphorus, dried and placed on cotton wool. Solidification in all cases produces heat.
Liquefaction produces cold.
In Masters's freezing apparatus certain measured quantities of crystallized sal-ammoniac, nitre, and nitrate of
ammonia, are placed in a metallic cylinder, surrounded with a small quantity of spring water contained in an
outer vessel. Directly the crystals are liquefied by the addition of water, intense cold is produced, which freezes
the water and forms an exact cast of the inner cylinder in ice, and this may afterwards be removed, by pouring
away the liquefied salts, and filling the inner cylinder, with water of the same temperature as the air, which
rapidly thaws the surrounding ice, and allows it to slip off into any convenient vessel ready to receive it. (Fig.
90.)
For an ingenious method of obtaining large and perfect crystals of almost any size, experimentalists are indebted
to Le Blanc. His method consists in first procuring small and perfect crystals—say, octohedra of alum—and then
placing them in a broad flat-bottomed pan, he pours over the crystals a quantity of saturated solution of alum,

obtained by evaporating a solution of alum until a drop taken out
crystallizes on cooling. The positions of the crystals are altered at least
once a day with a glass rod, so that all the faces may be alternately
exposed to the action of the solution, for the side on which the crystal
rests, or is in contact with the vessel, never receives any increment. The
crystals will thus gradually grow or increase in size, and when they have
done so for some time, the best and most symmetrical, may be removed
and placed separately, in vessels containing some of the same saturated
solution of alum, and being constantly turned they may be obtained of
almost any size desired.
Unless the crystals are removed to fresh solutions, a reaction takes place,
in consequence of the exhaustion of the alum from the water, and the
crystal is attacked and dissolved. This action is first perceptible on the
edges and angles of the crystal; they become blunted and gradually lose
their shape altogether. By this method crystals may be made to grow in
length or breadth—the former when they are placed upon their sides, the
latter if they be made to stand upon their bases.
On Le Blanc's principle, beautiful crystal baskets are made with alum,
sulphate of copper, and bichromate of potash. The baskets are usually
made of covered copper wire, and when the salts crystallize on them as a
nucleus or centre, they are constantly removed to fresh solutions, so that
the whole is completely covered, and red, white, and blue sparkling
crystal baskets formed. They will retain their brilliancy for any time, by Fig. 90.
placing them under a glass shade, with a cup containing a little water.
a. The inner cylinder which contains the freezing
The sketch below affords an excellent illustration of some of Nature's mixture. b b. The outer one containing spring
remarkable concretions in the peculiar columnar structure of basalt. water. c c. The ice slipping away from the inner
cylinder.

Fig. 91.
The Giant's Causeway.

CHAPTER X.
CHEMISTRY.

Fig 92
Alchemists at work
There is hardly any kind of knowledge which has been so slowly acquired as that of chemistry, and perhaps no
other science has offered such fascinating rewards to the labour of its votaries as the philosopher's stone, which
was to produce an unfailing supply of gold; or the elixir of life, that was to give the discoverer of the gold-
making art the time, the prolonged life, in which he might spend and enjoy it.
Hundreds of years ago Egypt was the great depository of all learning, art, and science, and it was to this ancient
country that the most celebrated sages of antiquity travelled.
Hermes, or Mercurius Trismegistus, the favourite minister of the Egyptian king Osiris, has been celebrated as
the inventor of the art of alchemy, and the first treatise upon it has been attributed to Zosymus, of Chemnis or
Panopolis. The Moors who conquered Spain were remarkable for their learning, and the taste and elegance with
which they designed and carried out a new style of architecture, with its lovely Arabesque ornamentation. They
were likewise great followers of the art of alchemy, when they ceased to be conquerors, and became more
reconciled to the arts of peace. Strange that such a people, thirsting as they did in after years for all kinds of
knowledge, should have destroyed, in the persons of their ancestors, the most numerous collection of books that
the world had ever seen: the magnificent library of Alexandria, collected by the Ptolemies with great diligence
and at an enormous expense, was burned by the orders of Caliph Omar; whilst it is stated that the alchemical

works had been previously destroyed by Diocletian in the fourth century, lest the Egyptians should acquire by
such means sufficient wealth to withstand the Roman power, for gold was then, as it is now, "the sinews of war."
Eastern historians relate the trouble and expense incurred by the succeeding Caliphs, who, resigning the
Saracenic barbarism of their ancestors, were glad to collect from all parts the books which were to furnish forth
a princely library at Bagdad. How the learned scholar sighs when he reads of seven hundred thousand books
being consigned to the ignominious office of heating forty thousand baths in the capital of Egypt, and of the
magnificent Alexandrian Library, a mental fuel for the lamp of learning in all ages, consumed in bath furnaces,
and affording six months' fuel for that purpose. The Arabians, however, made amends for these barbarous deeds
in succeeding centuries, and when all Europe was laid waste under the iron rule of the Goths, they became the
protectors of philosophy and the promoters of its pursuits; and thus we come to the seventh century, in which
Geber, an Arabian prince lived, and is stated to be the earliest of the true alchemists whose name has reached
posterity.
Without attempting to fill up the alchemical history of the intervening centuries, we leap forward six hundred
years, and now find ourselves in imagination in England, with the learned friar, Roger Bacon, a native of
Somersetshire, who lived about the middle of the thirteenth century; and although the continual study of
alchemy had not yet produced the "stone," it bore fruit in other discoveries, and Roger Bacon is said, with great
appearance of truth, to have discovered gunpowder, for he says in one of his works:—"From saltpetre and other
ingredients we are able to form a fire which will burn to any distance;" and again alluding to its effects, "a small
portion of matter, about the size of the thumb, properly disposed, will make a tremendous sound and
coruscation, by which cities and armies might be destroyed." The exaggerated style seems to have been a
favourite one with all philosophers, from the time of Roger Bacon to that of Muschenbroek of the University of
Leyden, who accidentally discovered the Leyden jar in the year 1746, and receiving the first shock, from a vial
containing a little water, into which a cork and nail had been fitted, states that "he felt himself struck in his arms,
shoulders, and breast, so that he lost his breath, and was two days before he recovered from the effects of the
blow and the terror;" adding, that "he would not take a second shock for the kingdom of France." Disregarding
the numerous alchemical events occurring from the time of Roger Bacon, we again advance four hundred years
—viz., to the year 1662, when, on the 15th of July, King Charles II. granted a royal charter to the Philosophical
Society of Oxford, who had removed to London, under the name of the Royal Society of London for Promoting
Natural Knowledge, and in the year 1665 was published the first number of the Philosophical Transactions; this
work contains the successive discoveries of Mayow, Hales, Black, Leslie, Cavendish, Lavoisier, Priestley, Davy,
Faraday; and since the year 1762 has been regularly published at the rate of one volume per annum. With this
preface proceed we now to discuss some of the varied phenomena of chemical attraction, or what is more
correctly termed

CHEMICAL AFFINITY.

The above title refers to an endless series of changes brought about by chemical combinations, all of which can
be reduced to certain fixed laws, and admit of a simple classification and arrangement. A mechanical
aggregation, however well arranged, can be always distinguished from a chemical one. Thus, a grain of
gunpowder consists of nitre, which can be washed away with boiling water, of sulphur, which can be sublimed
and made to pass away as vapour, of charcoal, which remains behind after the previous processes are complete;
this mixture has been perfected by a careful proportion of the respective ingredients, it has been wetted, and
ground, and pressed, granulated, and finally dried; all these mechanical processes have been so well carried out
that each grain, if analysed, would be similar to the other; and yet it is, after all, only a mechanical aggregation,
because the sulphur, the charcoal, and the nitre are unchanged. A grain of gunpowder moistened, crushed, and
examined by a high microscopic power, would indicate the yellow particles of sulphur, the black parts of
charcoal, whilst the water filtered from the grain of powder and dried, would show the nitre by the form of the
crystal. On the other hand, if some nitre is fused at a dull red heat in a little crucible, and two or three grains of
sulphur are added, they are rapidly oxidized, and combine with the potash, forming sulphate of potash; and after
this change a few grains of charcoal may be added in a similar manner, when they burn brightly, and are
oxidized and converted into carbonic acid, which also unites in like manner with the potash, forming carbonate
of potash; so that when the fused nitre is cooled and a few particles examined by the microscope, the charcoal
and sulphur are no longer distinguishable, they have undergone a chemical combination with portions of the

nitre, and have produced two new salts, perfectly different in taste, gravity, and appearance from the original
substances employed to produce them. Hence chemical combination is defined to be "that property which is
possessed by one or more substances, of uniting together and producing a third or other body perfectly different
in its nature from either of the two or more generating the new compound."
To return to our first experiment with the gunpowder: take sulphur, place some in an iron ladle, heat it over a gas
flame till it catches fire, then ascend a ladder, and pour it gently, from the greatest height you can reach, into a
pail of warm water: if this experiment is performed in a darkened room a magnificent and continuous stream of
fire is obtained, of a blue colour, without a single break in its whole length, provided the ladle is gradually
inclined and emptied. The substance that drops into the warm water is no longer yellow and hard, but is red, soft,
and plastic; it is still sulphur, though it has taken a new form, because that element is dimorphous (δις twice, and
μορφη a form), and, Proteus-like, can assume two forms. Take another ladle, and melt some nitre in it at a dull
red heat, then add a small quantity of sulphur, which will burn as before; and now, after waiting a few minutes,
repeat the same experiment by pouring the liquid from the steps through the air into water; observe it no longer
flames, and the substance received into the water is not red and soft and plastic, but is white, or nearly so, and
rapidly dissolves away in the water. The sulphur has united with the oxygen of the nitre and formed sulphuric
acid, which combines with the potash and forms sulphate of potash; here, then, oxygen, sulphur, and potassium,
have united and formed a salt in which the separate properties of the three bodies have completely disappeared;
to prove this, it is only necessary to dissolve the sulphate of potash in water, and after filtering the solution, or
allowing it to settle, till it becomes quite clear and bright, some solution of baryta may now be added, when a
white precipitate is thrown down, consisting of sulphate of baryta, which is insoluble in nitric or other strong
acids. The behaviour of a solution of sulphate of potash with a nitrate of baryta may now be contrasted with that
of the elements it contains; on the addition of sulphur to a solution of nitrate of baryta no change whatever takes
place, because the sulphur is perfectly insoluble. If a stream of oxygen gas is passed from a bladder and jet
through the same test, no effect is produced; the nitrate of baryta has already acquired its full proportion of
oxygen, and no further addition has any power to change its nature; finally, if a bit of the metal potassium is
placed in the solution of nitrate of baryta it does not sink, being lighter than water, and it takes fire; but this is
not in any way connected with the presence of the test, as the same thing will happen if another bit of the metal
is placed in water—it is the oxygen of the latter which unites rapidly with the potassium, and causes it to
become so hot that the hydrogen, escaping around the little red-hot globules, takes fire; moreover, the fact of the
combustion of the potassium under such circumstances is another striking proof of the opposite qualities of the
three elements—sulphur, oxygen, and potassium—as compared with the three chemically combined and forming
sulphate of potash. The same kind of experiment may be repeated with charcoal; if some powdered charcoal is
made red-hot, and then puffed into the air with a blowing machine, numbers of sparks are produced, and the
charcoal burns away and forms carbonic acid gas, a little ash being left behind; but if some more nitre be heated
in a ladle, and charcoal added, a brilliant deflagration (deflagro, to burn) occurs, and the charcoal, instead of
passing away in the air as carbonic acid, is now retained in the same shape, but firmly and chemically united
with the potash of the nitre, forming carbonate of potash, or pearl-ash, which is not black and insoluble in water
and acids like charcoal, but is white, and not only soluble in water, but is most rapidly attacked by acids with
effervescence, and the carbon escapes in the form of carbonic acid gas. Thus we have traced out the distinction
between mechanical aggregation and chemical affinity, taking for an example the difference between gunpowder
as a whole (in which the ingredients are so nicely balanced that it is almost a chemical combination), and its
constituents, sulphur, charcoal, and nitre, when they are chemically combined; or, in briefer language, we have
noticed the difference between the mechanical mixture, and some of the chemical combinations, of three
important elements. Our very slight and partial examination of three simple bodies does not, however, afford us
any deep insight into the principles of chemistry; we have, as it were, only mastered the signification of a few
words in a language; we might know that chien was the French for dog, or cheval horse, or homme man; but that
knowledge would not be the acquisition of the French language, because we must first know the alphabet, and
then the combination of these letters into words; we must also acquire a knowledge of the proper arrangement of
these words into sentences, or grammar, both syntax and prosody, before we can claim to be a French scholar: so
it is with chemistry—any number of isolated experiments with various chemical substances would be
comparatively useless, and therefore the "alphabet of chemistry," or "table of simple elements," must first be
acquired. These bodies are understood to be solids, fluids, and gases, which have hitherto defied the most
elaborate means employed to reduce them into more than one kind of matter. Even pure light is separable into
seven parts—viz., red, orange, yellow, green, blue, indigo, and violet; but the elements we shall now enumerate

are not of a compound, but, so far as we know, of an absolutely simple or single nature; they represent the
boundaries, not the finality, of the knowledge that may be acquired respecting them.
The elements are sixty-four in number, of which about forty are tolerably plentiful, and therefore common;
whilst the remainder, twenty-four, are rare, and for that reason of a lesser utility: whenever Nature employs an
element on a grand scale it may certainly be called common, but it generally works for the common good of all,
and fulfils the most important offices.
CLASSIFICATION OF THE ALPHABET OF CHEMISTRY.
13 Non-Metallic Bodies.

Combining
proportion
Name. Symbol.
or atomic
weight.
1.Oxygen O = 8
2.Hydrogen H = 1
3.Nitrogen N = 14
4.Chlorine Cl = 35.5
5.Iodine I = 127.1
6.Bromine Br = 80.0
7.Fluorine F = 18.9
8.Carbon C = 6
9.Boron B = 10.9
10.Sulphur Sv = 16
11. Phosphorus P = 32
12.Silicon Si = 21.3
13.Selenium Se = 39.5

51 Metals.
1. Aluminium Al = 13.7
2. Antimony Sb = 129
3. Arsenic As = 75
4. Barium Ba = 68.5
5. Bismuth Bi = 213
6. Cadmium Cd = 56
7. Calcium Ca = 20
8. Cerium Ce = 47
9. Chromium Cr = 26.7
10. Cobalt Co = 29.5
11. Copper Cu = 31.7
12. Donarium
13. Didymium D
14. Erbium E
15. Gold Au = 197
16. Glucinum Gl
17. Iron Fe = 28
18. Ilmenium Il
19. Iridium Ir = 99
20. Lead Pb = 103.7

21. Lanthanium La
22. Lithium Li = 6.5
23. Magnesium Mg = 12.2
24. Manganese Mn = 27.6
25. Mercury Hg = 100
26. Molybdenum Mo = 46
27. Nickel Ni = 29.6
28. Norium
29. Niobium Nb
30. Osmium Os = 99.6
31. Platinum Pt = 98.7
32. Potassium K = 39.2
33. Palladium Pd = 53.3
34. Pelopium Pe
35. Rhodium R = 52.2
36. Rhuthenium Ru = 52.2
37. Silver Ag = 108.1
38. Sodium Na = 23
39. Strontium Sr = 43.8
40. Tin Sn = 59
41. Tantalum Ta = 184
42. Tellurium Te = 64.2
43. Terbium Tb
44. Thorium Th = 59.6
45. Titanium Ti = 25
46. Tungsten W[A]= 95
47. Uranium U = 60
48. Vanadium V = 68.6
49. Yttrium Y
50. Zinc Zn = 32.6
51. Zirconium Zr = 22.4

(N.B. The elements printed in italics are at present unimportant.)
[A] From the mineral Wolfram, and now exceedingly valuable, as when alloyed with iron it is harder than, and will bore
through steel.

A few words will suffice to explain the meaning of the terms which head the names, letters, and numbers of the
Table of Elements. The names of the elements have very interesting derivations, which it is not the object of this
work to go into; the symbols are abbreviations, ciphers of the simplest kind, to save time and trouble in the
frequent repetition of long words, just as the signs + plus, and - minus, are used in algebraic formulæ. For
instance—the constant recurrence of water in chemical combinations must be named, and would involve the
most tedious repetition; water consists of oxygen and hydrogen, and by taking the first letter of each word we
have an instructive symbol, which not only gives us an abbreviated term for water, but also imparts at once a
knowledge of its composition by the use of the letters, HO.
Again, to take a more complex example, such as would occur in the study of organic chemistry—a sentence
such as the hydrated oxide of acetule, is written at once by C4H4O2, the figures referring to the number of
equivalents of each element—viz., 4 equivalents of C, the symbol for carbon, 4 of H (hydrogen), and 2 of O
(oxygen).

The long word paranaphthaline, a substance contained in coal tar, is disposed of at once with the symbols and
figures C30H12.

The figures in the third column are, however, the most interesting to the precise and mathematically exact
chemist. They represent the united labours of the most painstaking and learned chemists, and are the exact
quantities in which the various elements unite. To quote one example: if 8 parts by weight of oxygen—viz., the
combining proportions of that element—are united with 1 part by weight of hydrogen, also its combining
number, the result will be 9 parts by weight of water; but if 8 parts of oxygen and 2 parts of hydrogen were used,
one only of the latter could unite with the former, and the result would be the formation again of 9 parts of water,
with an overplus of 1 equivalent of hydrogen.
It is useless to multiply examples, and it is sufficient to know that with this table of numbers the figures of
analysis are obtained. Supposing a substance contained 27 parts of water, and the oxygen in this had to be
determined, the rule of proportion would give it at once, 9: 27:: 8: 24. 9 parts of water are to 27 parts as 8 of
oxygen (the quantity contained in 9 parts of water) are to the answer required—viz., 24 of oxygen. The names,
symbols, and combining proportions being understood, we may now proceed with the performance of many
interesting

CHEMICAL EXPERIMENTS.

As the permanent gases head the list, they will first engage our attention, beginning with the element oxygen—
Symbol O, combining proportion 8. There is nothing can give a better idea of the enormous quantity of oxygen
present in the animal, vegetable, and mineral kingdoms, than the statement that it represents one-third of the
weight of the whole crust of the globe. Silica, or flint, contains about half its weight of oxygen; lime contains
forty per cent.; alumina about thirty-three per cent. In these substances the element oxygen remains inactive and
powerless, chained by the strong fetters of chemical affinity to the silicium of the flint, the calcium of the lime,
and the aluminum of the alumina. If these substances are heated by themselves they will not yield up the large
quantity of oxygen they contain.
Nature, however, is prodigal in her creation, and hence we have but to pursue our search diligently to find a
substance or mineral containing an abundance of oxygen, and part of which it will relinquish by what used to be
called by the "old alchemists" the torture of heat. Such a mineral is the black oxide of manganese, or more
correctly the binoxide of manganese, which consists of one combining proportion of the metal manganese—viz.,
27.6, and two of oxygen—viz., 8 × 2 = 16. If three proportions of the binoxide of manganese are heated to
redness in an iron retort, they yield one proportion (equal to 8) of oxygen, and all that has just been explained by
so many words is comprehended in the symbols and figures below:—
3 MnO2 = Mn3O4 + O.

Thus the 3 MnO2 represent the three proportions of the binoxide of manganese before heat is applied, whilst the
sign =, the sign of equation (equal to), is intended to show that the elements or compounds placed before it
produce those which follow it; hence the sequel Mn3O4 + O shows that another compound of the metal and
oxygen is produced, whilst the + O indicates the liberated oxygen gas. The iron retort employed to hold the
mineral should be made of cast iron in preference to wrought iron, as the latter is very soon worn out by contact
with oxygen at a red heat. A gun-barrel will answer the purpose for an experiment on the small scale, to which
must be adapted a cock and piece of pewter tubing. Such a make-shift arrangement may do very well when
nothing better offers; but as a question of expense, it is probably cheaper in the end to order of Messrs. Simpson
and Maule, or of Messrs. Griffin, or of Messrs. Bolton, a cast-iron bottle, or cast-iron retort, as it is termed, of a
size sufficient to prepare two gallons of oxygen from the binoxide of manganese, which, with four feet of iron
conducting-pipe, and connected to the bottle with a screw, does not cost more than six shillings—an enormous
dip, perhaps, in the juvenile pocket, and therefore we shall indicate presently a still cheaper apparatus for the
same purpose. (Fig. 93.)

Fig. 93.
a. The iron bottle, containing the black oxide of manganese, with pipe passing to the pneumatic trough, b b, in which is fixed a
shelf, c, perforated with a hole, under which the end of the pipe is adjusted, and the gas passes into the gas-jar, d.

The oxygen is conveyed to a square tin box provided with a shelf at one end, perforated with several holes at
least one inch in diameter, called the pneumatic trough; any wooden trough, butter or wash-tub, foot-pan or bath,
provided with a shelf, may be raised by the same title to the dignity of a piece of chemical apparatus. The gas jar
must be filled with water by withdrawing the stopper and pressing it down into the trough, and when the neck is
below the level of the water, the stopper is again inserted, and the jar with the water therein contained lifted
steadily on to the shelf, the entry of atmospheric air being prevented by keeping the lower part of the gas jar,
called the welt, under the water. Sometimes the pneumatic trough contains so small a quantity of water that on
raising the gas jar to the shelf the liquid does not cover the bottom, and the air rushes up in large bubbles. Under
these circumstances it is better to provide a gallon stone jug full of water, so that when the jar is being raised to
the shelf it may be thrust into the trough (on the same principle as the crow and the pitcher in the fable), and thus
by its bulk (as the stones in the pitcher) raise the water to the proper level. When the gas jar is about half filled
with gas the jug may be withdrawn. This arrangement saves the trouble of constantly adding and baling out
water from the pneumatic trough. (Fig. 94.)

Fig. 94.
a a. Pneumatic trough, with gas jar raised to shelf; bubbles of air are rushing in at b, as the level of the water is below the shelf
—viz., at c c. d d. Same trough and gas jar with water kept over the shelf by the introduction of the stone pitcher e, full of
water.

There are other solid oxygenized bodies in which the affinities are less powerful, and hence a lower degree of
heat suffices to liberate the oxygen gas, and one of the most useful in this respect is the salt termed chlorate of
potash. If the substance is heated by itself, the temperature required to expel the oxygen is almost as high as that
demanded for the black oxide of manganese; but, strange to say, if the two substances are reduced to powder,
and mixed in equal quantities by weight, then a very moderate increase of heat is sufficient to cause the chlorate
of potash to give up its oxygen, whilst the oxide of manganese undergoes no change whatever. It seems to fulfil

only a mechanical office—possibly that of separating each particle of chlorate of potash from the other, so that
the heat attacks the substance in detail, just as a solid square of infantry might repel almost any attack, whilst the
same body dispersed over a large space might be of little use; so with the chlorate of potash, which undergoes
rapid decomposition when mixed with and divided amongst the particles of the oxide of manganese; less so with
the red oxide of iron, and still less with sand or brick-dust. (Fig. 95.)

Fig. 95.
Preparation of oxygen from chlorate of potash and oxide of manganese.

KO.ClO5 = KCl + O6.

This curious fact is explained usually by reference to what is called catalytic action, or decomposition by contact
(κατα, downwards, and λυω, I unloosen), being a power possessed by a body of resolving another into a new
compound without undergoing any change itself. To make this term still clearer, we may notice another example
in linen rags, which may be exposed for any length of time to the action of water without fear of conversion into
sugar; if, however, oil of vitriol is first added to the linen rags, and they are subsequently digested at a proper
temperature with water, then the rags are converted into sugar (the author has seen a specimen made of an "old
shirt"); but, curious to relate, the oil of vitriol is unchanged in the process, and if the process be commenced with
a pound of acid, the same quantity is discoverable at the end of the chemical decomposition of the linen rags,
and their conversion into sugar.
If a mixture of equal parts of oxide of manganese and chlorate of potash is placed in a clean Florence flask, with
a cork, and pewter, or glass tube attached, great quantities of oxygen are quickly liberated, on the application of
the heat of a spirit lamp. Such a retort would cost about fourpence, and if the flask is broken in the operation it
can be easily replaced by another, value one penny, as the same cork and tube will generally suit a number of
these cheap glass vessels. Corks may always be softened by using either a proper cork squeezer, or by placing
them under a piece of board or a flat surface, and rolling and pressing the cork till quite elastic.
Whilst fitting the latter into the neck of a flask, it is perhaps safer to hold the thin and fragile vessel in a cloth, so
that if the flask breaks the chemical experiment may not be arrested for many days by the severe cutting and
wounding of the fingers. After the cork is fitted, it is to be removed from the flask and bored with a cork borer.
This useful tool is sold in complete sets to suit all sizes of glass tubes, and the pewter or glass being inserted, the
flask and tube will be ready for use, provided the tube is bent to the proper curve. This is easy enough to perform
with the pewter, but not quite so easy with the glass tube, which must be held over the flame of a spirit lamp till
soft, and then bent very gradually to the proper curve. If a short length of the glass tube is heated, it bends too
sharply, and the convexity of the glass is flattened, whilst the internal diameter of the tube is lessened, so that at
least three inches in length should be warmed, and the heat must not be continued in one place only, but should
be maintained in the direction of the bend, the whole manipulation being conducted without any hurry. (Fig. 96.)

Fig. 96.
a. The cork squeezer. b. The cork borers. c. The operation of bending the glass tube over the flame of the spirit-lamp. d. The
neck of the flask, with cork and tube bent and fitted complete for use.

Having filled a gas jar with oxygen, it may be removed from the pneumatic trough by sliding it into a plate
under the surface of the water, and to prevent the stopper being thrust out accidentally from the jar by the
upward pressure of the gas, whilst a little compressed, during the act of passing it into the plate, it is advisable to
hold the stopper of the jar firmly but gently, so that it cannot slip out of its place. A number of jars of oxygen
may be prepared and arranged in plates, all of which of course must contain a little water, and enough to cover
the welt of the jar.

EXPERIMENTS WITH OXYGEN GAS.

This gas was originally discovered by Priestley, in August, 1774, and was first obtained by heating red
precipitate—i.e., the red oxide of mercury.
HgO = Hg + O.
We leave these symbols and figures to be deciphered by the youthful philosopher with the aid of the table of
elements, &c., and return to the experiments.
There are certain thin wax tapers like waxed cord, called bougies, which can be bent to any shape, and are very
convenient for experiments with the gases. If one of these tapers is bent as in Fig. 97, then lighted and allowed to
burn for some minutes, a long snuff is gradually formed, which remains in a state of ignition when the flame of
the taper is blown out. On plunging this into a jar of oxygen, it instantly re-lights with a sort of report, and burns
with greatly-increased brilliancy, as described by Dr. Priestley in his first experiment with this gas, and so
elegantly repeated by Professor Brande in his refined dissertation on the progress of chemical science.
"The 1st of August, 1774, is a red-letter day in the annals of chemical philosophy, for it was then that Dr.
Priestley discovered dephlogisticated air. Some, sporting in the sunshine of rhetoric, have called this the birthday
of pneumatic chemistry; but it was even a more marked and memorable period; it was then (to pursue the
metaphor) that this branch of science, having eked out a sickly and infirm infancy in the ill-managed nursery of
the early chemists, began to display symptoms of an improving constitution, and to exhibit the most hopeful and
unexpected marks of future importance. The first experiment, which led to a very satisfactory result, was
concluded as follows:—A glass jar was filled with quicksilver, and inserted in a basin of the same; some red
precipitate of quicksilver was then introduced, and floated upon the quicksilver in the jar; heat was applied to it
in this situation with a burning-lens, and to use Priestley's own words, I presently found that air was expelled
from it very readily. Having got about three or four times as much as the bulk of my materials, I admitted water
into it, and found that it was not imbibed by it. But what surprised me more than I can well express was, that a
candle burned in this air with a remarkably vigorous flame, very much like that enlarged flame with which a
candle burns in nitrous air exposed to iron or lime of sulphur (i.e., laughing gas); but as I had got nothing like
this remarkable appearance from any kind of air besides this peculiar modification of nitrous air, and I knew no

nitrous acid was used in the preparation of mercurius calcinatus, I was utterly at a
loss how to account for it." (Fig. 98.)

Fig. 98.
a. Glass vessel full of mercury, containing the red precipitate at the top, and standing in the dish b,
also containing mercury. c. The burning-glass concentrating the sun's rays on the red precipitate,
Fig. 97. being Priestley's original experiment.

Second Experiment.

The term oxygen is derived from the Greek (οζυς, acid, and γενναω, I give rise to), and was originally given to
this element by Lavoisier, who also claimed its discovery; and if this honour is denied him, surely he has
deserved equal scientific glory in his masterly experiments, through which he discovered that the mixture of
forty-two parts by measure of azote, with eight parts by measure of oxygen, produced a compound precisely
resembling our atmosphere. The name given to oxygen was founded on a series of experiments, one of which
will now be mentioned.
Place some sulphur in a little copper ladle attached to a wire, and called a deflagrating spoon, passed through a
round piece of zinc or brass plate and cork, so that the latter acts as an adjusting arrangement to fix the wire at
any point required. The combustion of the sulphur, previously feeble, now assumes a remarkable intensity, and a
peculiar coloured light is generated, whilst the sulphur unites with the oxygen, and forms sulphurous acid gas. It
produces, in fact, the same gas which is formed by burning an ordinary sulphur match. This compound is
valuable as a disinfectant, and is a very important bleaching agent, being most extensively employed in the
whitening of straw employed in the manufacture of straw bonnets. It is an acid gas, as Lavoisier found, and this
property may be detected by pouring a little tincture of litmus into the bottom of the plate in which the gas jar
stands. The blue colour of the litmus is rapidly changed to red, and it might be thought that no further argument
could possibly be required to prove that oxygen was the acidifying agent, the more particularly as the result is
the same in the next illustration.

Fig. 99.
a. The deflagrating
spoon, b. The cork. c.
The zinc, or brass, or tin
plate. d d. The gas jar.

Third Experiment.

Cut a small piece from an ordinary stick of phosphorus under water, take care to dry it properly with a cloth, and
after placing it in a deflagrating spoon, remove the stopper from the gas-jar, as there is no fear of the oxygen
rushing away, because it is somewhat heavier than atmospheric air; and then, after placing the spoon with the
phosphorus in the neck of the jar, apply a heated wire and pass the spoon at once into the middle of the oxygen;
in a few seconds a most brilliant light is obtained, and the jar is filled with a white smoke; as this subsides, being
phosphoric acid, and perfectly soluble in water, the same litmus test may be applied, when it is in like manner
changed to red. The acid obtained is one of the most important constituents of bone.

Fourth Experiment.

A bit of bark-charcoal bound round with wire is set on fire either by holding it in the flame of a spirit-lamp, or
by attaching a small piece of waxed cotton to the lower part, and igniting this; the charcoal may then be inserted
into a bottle of oxygen, when the most brilliant scintillations occur. After the combustion has ceased and the
whole is cool, a little tincture of litmus may also be poured in and shaken about, when it likewise turns red,
proving for the third time the generation of an acid body, called carbonic acid—an acid, like the others already
mentioned, of great value, and one which Nature employs on a stupendous scale as a means of providing plants,
&c., with solid charcoal. Carbonic acid, a virulent poison to animal life, is, when properly diluted, and as
contained in atmospheric air, one of the chief alimentary bodies required by growing and healthy plants.
In three experiments acid bodies have been obtained; can we speculate on the result of the next?

Fifth Experiment.

Into a deflagrating spoon place a bit of potassium, set this on fire by holding it in the spoon in the flame of a
spirit-lamp, and then rapidly plunge the burning metal into a bottle of oxygen. A brilliant ignition occurs in the
deflagrating spoon for a few seconds, and there is little or no smoke in the jar. The product this time is a solid,
called potash, and if this be dissolved in water and filtered, it is found to be clear and bright, and now on the
addition of a little tincture of litmus to one half of the solution, it is wholly unaffected, and remains blue; but if
with the other half a small quantity of tincture of turmeric is mixed, it immediately changes from a bright yellow
solution to a reddish-brown, because turmeric is one of the tests for an alkali; and thus is ascertained by the help
of this and other tests that the result of the combustion is not an acid, but an alkali. The experiment is made still
more satisfactory by burning another bit of potassium in oxygen and dissolving the product in water, and if any
portion of the reddened liquid derived from the sulphurous, phosphoric, and carbonic acids taken from the
previous experiments, be added to separate portions of the alkaline solution, they are all restored to their original
blue colour, because an acid is neutralized by an alkali; and the experiment is made quite conclusive by the
restoration of the reddened turmeric to a bright yellow on the addition of a solution of either of the three acids
already named. Moreover, an acid need not contain a fraction of oxygen, as there is a numerous class of
hydracids, in which the acidifying principle is hydrogen instead of oxygen, such as the hydrochloric, hydriodic,
hydro-bromic, and hydrofluoric acids.

Sixth Experiment.

A piece of watch-spring is softened at one end, by holding it in the flame of a spirit-lamp, and allowing it to
cool. A bit of waxed cotton is then bound round the softened end, and after being set on fire, is plunged into a
gas jar containing oxygen; the cotton first burns away, and then the heat communicates to the steel, which
gradually takes fire, and being once well ignited, continues to burn with amazing rapidity, forming drops of
liquid dross, which fall to the bottom of the plate—and also a reddish smoke, which condenses on the sides of
the jar; neither the dross which has dropped into the plate, nor the reddish matter condensed on the jar, will
affect either tincture of litmus or turmeric; they are neither acid nor alkaline, but neutral compounds of iron,
called the sesquioxide of iron (Fe2O3), and the magnetic oxide (Fe3O4 = FeO.Fe2O3).

Seventh Experiment.

Some oxygen gas contained in a bladder provided with a proper jet may be squeezed out, and upon, some liquid
phosphorus contained in a cup at the bottom of a finger glass full of boiling water, when a most brilliant
combustion occurs, proving that so long as the principle is complied with—viz., that of furnishing oxygen to a
combustible substance—it will burn under water, provided it is insoluble, and possesses the remarkable affinity
for oxygen which belongs to phosphorus. The experiment should be performed with boiling water, to keep the
phosphorus in the liquid state; and it is quite as well to hold a square foot of wire gauze over the finger glass
whilst the experiment is being performed. (Fig. 100.)

Fig. 100.
a. Bladder containing oxygen, provided with a stop-cock and jet leading to, b, b. Finger glass containing boiling water. c. The
cup of melted phosphorus under the water. The gas escapes from the bladder when pressed.

Eighth Experiment.

Oxygen is available from many substances when they are mixed with combustible substances, and hence the
brilliant effects produced by burning a mixture of nitre, meal powder, sulphur, and iron or steel filings; the metal

burns with great brilliancy, and is projected from the case in most beautiful sparks, which are long and needle-
shaped with steel, and in the form of miniature rosettes with iron filings; it is the oxygen from the nitre that
causes the combustion of the metal, the other ingredients only accelerate the heat and rate of ignition of the
brilliant iron, which is usually termed a gerb.

Ninth Experiment.

A mixture of nitrate of potash, powdered charcoal, sulphur, and nitrate of strontium, driven into a strong paper
case about two inches long, and well closed at the end with varnish, being quite waterproof, may be set on fire,
and will continue to burn under water until the whole is consumed; the only precaution necessary being to burn
the composition from the case with the mouth downward, and if the experiment is tried in a deep glass jar it has
a very pleasing effect. (Fig. 101.)

Fig. 101.
a. Case of red fire burning downwards, and attached by a copper wire to a bit of leaden pipe b, to sink it. c c. Jar containing
water.

The red-fire composition is made by mixing nitrate of strontia 40 parts by weight, flowers of sulphur 13 parts,
chlorate of potash 5 parts, sulphuret of antimony 4 parts. These ingredients must first be well powdered
separately, and then mixed carefully on a sheet of paper with a paper-knife. They are liable to explode if rubbed
together in a mortar, on account of the presence of sulphur and chlorate of potash, and the composition, if kept
for any time, is liable to take fire spontaneously.

Tenth Experiment.

Some zinc is melted in an iron ladle, and made quite red hot; if a little dry nitre is thrown upon the surface, and
gently stirred into the metal, it takes fire with the production of an intense white light, whilst large quantities of
white flakes ascend, and again descend when cold, being the oxide of zinc, and called by the alchemists the
"Philosopher's Wool" (ZnO). In this experiment the oxygen from the nitre effects the oxidation of the metal zinc.

Eleventh Experiment.

A mixture of four pounds of nitre with two of sulphur and one and a half of lamp black produces a most
beautiful and curious fire, continually projected into the air as sparks having the shape of the rowel of a spur, and
one that may be burnt with perfect safety in a room, as the sparks consume away so rapidly, in consequence of

the finely divided condition of the charcoal, that they may be received on a handkerchief or the hand without
burning them. The difficulty consists in effecting the complete mixture of the charcoal. The other two
ingredients must first be thoroughly powdered separately, and again triturated when mixed, and finally the
charcoal must be rubbed in carefully, till the whole is of a uniform tint of grey and very nearly black, and as the
mixture proceeds portions must be rammed into a paper case, and set on fire; if the stars or pinks come out in
clusters, and spread well without other and duller sparks, it is a sign that the whole is well mixed; but if the
sparks are accompanied with dross, and are projected out sluggishly, and take some time to burn, the mixture
and rubbing in the mortar must be continued; and even that must not be carried too far, or the sparks will be too
small. N.B.—If the lamp-black was heated red hot in a close vessel, it would probably answer better when cold
and powdered.

Twelfth Experiment.

Into a tall gas jar with a wide neck project some red-hot lamp-black through a tin funnel, when a most brilliant
flame-like fire is obtained, showing that finely divided charcoal with pure oxygen would be sufficient to afford
light; but as the atmosphere consists of oxygen diluted with nitrogen, compounds of charcoal with hydrogen, are
the proper bodies to burn, to produce artificial light.

Thirteenth Experiment. The Bude Light.

This pretty light is obtained by passing a steady current of oxygen gas (escaping at a very low pressure) through
and up the centre pipe of an argand oil lamp, which must be supplied with a highly carbonized oil and a very
thick wick, as the oxygen has a tendency to burn away the cotton unless the oil is well supplied, and allowed to
overflow the wick, as it does in the lamps of the lighthouses. The best whale oil is usually employed, though it
would be worth while to test the value of Price's "Belmontine Oil" for the same purpose. (Fig. 102.)

Fig. 102.
a. Reservoir of oil. b. The flexible pipe conveying oxygen to centre of the argand lamp.

Fourteenth Experiment. A Red Light.

Clear out the oil thoroughly from the Bude light apparatus; or, what is better, have two lamps, one for oil, and
the other for spirit; fill the apparatus with a solution of nitrate of strontia and chloride of calcium in spirits of
wine, and let it burn from the cotton in the same way as the oil, and supply it with oxygen gas.

Fifteenth Experiment. A Green Light.

Dissolve boracic acid and nitrate of baryta in spirits of wine, and supply the Bude lamp with this solution.

Sixteenth Experiment. A Yellow Light.

Dissolve common salt in spirits of wine, and burn it as already described in the Bude light apparatus.

Seventeenth Experiment. The Oxy-calcium Light.

This very convenient light is obtained in a simple manner, either by using a jet of oxygen as a blowpipe to
project the flame of a spirit lamp on to a ball of lime; or common coal-gas is employed instead of the spirit lamp,
being likewise urged against a ball of lime. By this plan one bag containing oxygen suffices for the production of
a brilliant light, not equal, however, to the oxy-hydrogen light, which will be explained in the article on
hydrogen. (Fig. 103.)

Fig. 103.
No. 1. a. Oxygen jet. b. The ball of lime, suspended by a wire. c. Spirit lamp. No. 2. d. Oxygen jet. e. Gas (jet connected with
the gas-pipe in the rear by flexible pipe) projected on to ball of lime, f.

Eighteenth Experiment.

To show the weight of oxygen gas, and that it is heavier than air, the stoppers from two bottles containing it may
be removed, one bottle may be left open for some time and then tested by a lighted taper, when it will still
indicate the presence of the gas, whilst the other may be suddenly inverted over a little cup in which some ether,
mixed with a few drops of turpentine, may be burning—the flame burns with much greater brilliancy at the
moment when the oxygen comes in contact with it.

Nineteenth Experiment.

The theory of the effect of oxygen upon the system when inhaled would be an increase in the work of the
respiratory organs; and it is stated that after inhaling a gallon or so of this gas, the pulse is raised forty or fifty
beats per minute: the gas is easily inhaled from a large india-rubber bag through an amber mouthpiece; it must of
course be quite pure, and if made from the mixture of chlorate of potash and oxide of manganese, should be
purified by being passed through lime and water, or cream of lime.

Twentieth Experiment.

There are certain colouring matters that are weakened or destroyed by the action of light and other causes, which
deprive them of oxygen gas or deoxidize them. A weak tincture of litmus, if long kept, often becomes colourless,
but if this colourless fluid is shaken in a bottle with oxygen gas it is gradually restored; and if either litmus,
turmeric, indigo, orchil, or madder, paper, or certain ribbons dyed with the same colouring matters, have become

faded, they may be partially restored by damping and placing them in a bottle of oxygen gas. The effect of the
oxygen is to reverse the deoxidizing process, and to impart oxygen to the colouring matters. By a peculiar
process indigo may be obtained quite white, and again restored to its usual blue colour, either by exposure to the
air or by passing a stream of oxygen through it.

Twenty-first Experiment.

Messrs. Matheson, of Torrington-street, Russell-square, prepare in the form of wire some of the rarest metals,
such as magnesium, lithium, &c. A wire of the metal magnesium burns magnificently in oxygen gas, and forms
the alkaline earth magnesia. The metal lithium, to which such a very low combining proportion belongs—viz.,
6.5, can also be procured in the state of wire, and burns in oxygen gas with an intense white light into the
alkaline lithia, which dissolved in alcohol with a little acetic acid, and burnt, affords a red flame, making a
curious contrast between the effects of colour produced by the metallic and oxidized state of lithium.

THE ALLOTROPIC CONDITION OF OXYGEN GAS.

The term allotropy (from αλλοτροπος, of a different nature) was first used by the renowned chemist Berzelius.
Dimorphism, or diversity in crystalline form, is therefore a special case of allotropy, and is most amusingly
illustrated with the iodide of mercury (HgI), which is made either by rubbing together equal combining
proportions of mercury and iodine (both of which are to be found in the Table of Elements, page 86, or by
carefully precipitating a solution of corrosive sublimate (chloride of mercury (HgCl)) with one of iodide of
potassium, just enough and no more of the latter being added to precipitate the metal, or else the iodide of
mercury is redissolved by the excess of the precipitant. It is first of a dirty yellow, and then gradually changes
when stirred to a scarlet; if this be collected on a filter, and washed and drained, it is a beautiful scarlet, and
when some of this substance is rubbed across a sheet of paper, a bright scarlet is apparent, which may be rapidly
changed to a lemon-yellow by heating the paper over the flame of a spirit lamp; and the iodide of mercury is
again brought back to a scarlet colour by rubbing down the yellow crystals with the fingers. This experiment
may be repeated over and over again with the like results. If some of the scarlet iodide of mercury is sublimed
from one bit of glass to another, it forms crystals, derived from the right rhombic prism; when these are
scratched with a pin they change again to the scarlet state, the latter when crystallized being in the form of the
square-based octohedron.
Other cases of dimorphism may be mentioned—viz., with sulphur, carbonate of lime, and lead, and many others,
whilst allotropy is curiously illustrated in the various conditions of charcoal, which, in the more numerous
examples, is black and opaque, and in another instance transparent like water. Lamp-black is soft, but the
diamond is the hardest natural substance. The allotropic state of sulphur has been already alluded to;
phosphorus, again, exists in three modifications: 1st, Common phosphorus, which shines in the dark and emits a
white smoke. 2nd, White phosphorus. 3rd, Red or amorphous phosphorus, which does not shine or emit white
smoke when exposed to the air, and is so altered in its properties that it may be safely carried in the pocket.
Enough evidence has therefore been offered to show that the allotropic property is not confined to one element
or compound, but is discoverable in many bodies, and in no one more so than in the allotropic state of the
element oxygen called

OZONE.

The Greek language has again been selected by the discoverer, Schönbein, of Basle, for the title or name of this
curious modification of oxygen, and it is so termed from οξειν, to smell. The name at once suggests a marked
difference between ozone and oxygen, because the latter is perfectly free from odour, whilst the former has that
peculiar smell which is called electric, and is distinguishable whenever an electrical machine is at work, or if a
Leyden jar is charged by the powerful Rhumkoff, or Hearder coil; it is also apparent when water is decomposed
by a current of electricity and resolved into its elements, oxygen and hydrogen. When highly concentrated it
smells like chlorine; and the author recollects seeing the first experiments by Schönbein, in England, at Mr.
Cooper's laboratory in the Blackfriars-road. Ozone is prepared by taking a clean empty bottle, and pouring

therein a very little distilled water, into which a piece of clean scraped phosphorus is introduced, so as to expose
about one-half of its diameter to the air in the bottle, whilst the other is in contact with the water. (Fig. 104.)
For the sake of precaution, the bottle may stand in a basin or soup plate, so that if the phosphorus should take
fire, it may be instantly extinguished by pouring cold water into the bottle, and should this crack and break, the
phosphorus is received into the plate.

Fig. 104.
a. A quart bottle, with the stopper loosely placed therein. b. The stick of clean phosphorus. c. The water level just to half the
thickness of the phosphorus. d d. A soup-plate.

When the ozone is formed the phosphorus can be withdrawn, and the phosphorous-acid smoke washed out by
shaking the bottle; it is distinguishable by its smell, and also by its action on test paper, prepared by painting
with starch containing iodide of potassium on some Bath post paper; when this is placed in the bottle containing
ozone, it changes the test blue, or rather a purplish blue.
Ozone is a most energetic body, and a powerful bleaching agent; if a point is attached to the prime conductor of
an electrical machine, and the electrified air is received into a bottle, it will be found to smell, and has the power
of bleaching a very dilute solution of indigo. Ozone is not a mere creation of fancy, as it can not only be
produced by certain methods, but may be destroyed by a red heat. If a point is prepared with a loop of platinum
wire, and this latter, after being connected with a voltaic battery, made red hot, and the whole placed on an
insulating stool, and connected with the prime conductor of an electrical machine, it is found that the electrified
air no longer smells, the ozone is destroyed; on the other hand, if the voltaic battery is disconnected, and the
electrified air again allowed to pass from the cold platinum wire, the smell is again apparent, the air will bleach,
and if caused to impinge at once upon the iodide of starch test, changes it in the manner already described. (Fig.
105.)

Fig. 105.
v. A small voltaic battery standing on the stool with glass legs, s s, and capable of heating a thin length of platinum wire about
two inches long, and bent to form a point between the conducting wires, w w.—N.B. The voltaic current can be cut off at
pleasure, so as to cool the wire when necessary. a is the prime conductor of an ordinary cylinder electrical machine. b is the
wire conveying the frictional electricity to the conducting wires of the voltaic battery, where the point p being the sharpest point
in the arrangement, delivers the electrified and ozonized air.

Ozone is insoluble in water, and oxidizes silver and lead leaf, finely powdered arsenic and antimony; it is a
poison when inhaled in a concentrated state, whilst diluted, and generated by natural processes, it is a beneficent
and beautiful provision against those numerous smells originating from the decay of animal and vegetable
matter, which might produce disease or death: ozone is therefore a powerful disinfectant. The test for ozone is
made by boiling together ten parts by weight of starch, one of iodide of potassium, and two hundred of water; it
may either be painted on Bath post paper, and used at once, or blotting paper may be saturated with the test and
dried, and when required for use it must be damped, either before or after testing for ozone, as it remains
colourless when dry, but becomes blue after being moistened with water.
Paper prepared with sulphate of manganese is an excellent test for ozone, and changes brown rapidly by the
oxidation of the proto-salt of manganese, and its conversion into the binoxide of the metal.
Ozone is also prepared by pouring a little sulphuric ether into a quart bottle, and then, after heating a glass rod in
the flame of the spirit lamp, it may be plunged into the bottle, and after remaining there a few minutes ozone
may be detected by the ordinary tests.

NITROGEN, OR AZOTE.

Νιτρον, nitre; γενναω, I form; α, privative; ζωη, life. Symbol, N; combining proportion, 14. Also termed by
Priestley, phlogisticated air.
In the year 1772, Dr. Rutherford, Professor of Botany in the University of Edinburgh, published a thesis in Latin
on fixed air, in which he says:—"By the respiration of animals healthy air is not merely rendered mephitic (i.e.,
charged with carbonic acid gas), but also suffers another change. For after the mephitic portion is absorbed by a
caustic alkaline lixivium, the remaining portion is not rendered salubrious; and although it occasions no
precipitate in lime-water, it nevertheless extinguishes flame and destroys life." Such is the doctor's account of the
discovery of nitrogen, which may be separated from the oxygen in the air in a very simple manner. The
atmosphere is the great storehouse of nitrogen, and four-fifths of its prodigious volume consist of this element.
Composition of Atmospheric Air.

Bulk. Weight.
Oxygen 20 22.3
Nitrogen 80 77.7
--- -----
100 100.

The usual mode of procuring nitrogen gas is to abstract or remove the oxygen
from a given portion of atmospheric air, and the only point to be attended to, is
to select some substance which will continue to burn as long as there is any
oxygen left. Thus, if a lighted taper is placed in a bottle of air, it will only burn
for a certain period, and is gradually and at last extinguished; not that the whole
of the oxygen is removed or changed, because after the taper has gone out, some
burning sulphur may be placed in the vessel, and will continue to burn for a
limited period; and even after these two combustibles have, as it were, taken
their fill of the oxygen, there is yet a little left, which is snapped up by burning
phosphorus, whose voracious appetite for oxygen is only appeased by taking the
whole. It is for this reason that phosphorus is employed for the purpose of
removing the oxygen, and also because the product (phosphoric acid) is
perfectly soluble in water, and thus the oxygen is first combined, and then
washed out of a given volume of air, leaving the nitrogen behind.

First Experiment.

To prepare nitrogen gas, it is only necessary to place a little dry phosphorus in a
Berlin porcelain cup on a wine glass, and to stand them in a soup plate
containing water. The phosphorus is set on fire with a hot wire, and a gas jar or
cylindrical jar is then carefully placed over it, so that the welt of the jar stands in
the water in the soup plate. At first, expansion takes place in consequence of the
heat, but this effect is soon reversed, as the oxygen is converted into a solid by
union with the phosphorus, forming a white smoke, which gradually disappears.
(Fig. 106.)

Fig. 106.
a. Cylindrical glass vessel, open at one end, and inverted over b, the wine-glass, supporting
c, the cup containing the burning phosphorus, and the whole standing in a soup-plate, d d,
containing water.

Supposing two grains of phosphorus had been placed in a platinum tube, and
just enough atmospheric air passed over it to convert the whole into phosphoric
acid, the weight of the phosphorus would be increased to 4½ grains by the
addition of 2½ grains of oxygen; now one cubic inch of oxygen weighs 0.3419,
or about 1/3rd of a grain, hence 7.3 cubic inches of oxygen disappear, which
weigh as nearly as possible 2½ grains, so that as 36.5 cubic inches of air contain
7.3 cubic inches of oxygen, that quantity of air must have passed over the 2
grains of phosphorus to convert it into 4½ grains of phosphoric acid.
For very delicate purposes, nitrogen is best prepared by passing air over finely-
divided metallic copper heated to redness; this metal absorbs the whole of the
oxygen and leaves the nitrogen. The finely-divided copper is procured by
passing hydrogen gas over pure black oxide of copper.

Second Experiment.

Fig. 107.
a. Glass jar, with collar of leather, through which the stamper, c, works. b b. The tube
containing the finely-divided lead, part of which falls out, and is ignited, and retained by
the little tray just below, being part of the iron stand, d d, with crutches supporting the ends
of the glass tube, and the whole stands in the dish of water, e e.

A very instructive experiment is performed by heating a good mass of tartrate of
lead in a glass tube which is hermetically sealed, and being placed on an iron
support, is then covered by a capped air jar with a sliding rod and stamper, the
whole being arranged in a plate containing water. When the stamper is pushed
down upon the glass the latter is broken (Fig. 107), and the air gradually
penetrates to the finely divided lead, when ignition occurs, and the oxygen is
absorbed, as demonstrated by the rise of the water in the jar. On the same
principle, if a bottle is filled about one-third full with a liquid amalgam of lead
and mercury, and then stopped and shaken for two hours or more, the finely
divided lead absorbs the oxygen and leaves pure nitrogen. Or if a mixture of
equal weights of sulphur and iron filings, is made into a paste with water in a
thin iron cup, and then warmed and placed under a gas jar full of air standing on
the shelf of the pneumatic trough, or in a dish full of water, the water gradually
rises in the jar in about forty-eight hours, in consequence of the absorption of the
oxygen gas.

Third Experiment.

Nitrogen is devoid of colour, taste, smell, of alkaline or acid qualities; and, as we
shall have occasion to notice presently, it forms an acid when chemically united
with oxygen, and an alkali in union with hydrogen. A lighted taper plunged into
this gas is immediately extinguished, while its specific gravity, which is lighter
than that of oxygen or air, is demonstrated by the rule of proportion.

Weight of 100 cubic Weight of 100 cubic
inches of air at inches of nitrogen at Specific gravity of
Unity.
60° Fahr., 60° Fahr., nitrogen.
bar. 29.92 in. bar. 29.92 in.
30.829 : 1 :: 29.952 : 971

And its levity may be shown very prettily by a simple experiment. Select two
gas jars of the same size, and after filling one with oxygen gas and the other with
nitrogen gas, slide glass plates over the bottoms of the jars, and proceed to invert
the one containing oxygen, placing the neck in a stand formed of a box open at
the top; then place the jar containing nitrogen over the mouth of the first,
withdrawing the glass plates carefully; and if the table is steady the top gas jar
will stand nicely on the lower one. Then (having previously lighted a taper so as
to have a long snuff) remove the stopper from the nitrogen jar and insert the
lighted taper, which is immediately extinguished, and as quickly relighted by
pushing it down to the lower jar containing the oxygen. This experiment may be
repeated several times, and is a good illustration of the relative specific gravities
of the two gases, and of the importance of the law of universal diffusion already
explained at p. 6, by which these gases mix, not combine together, and the
atmosphere remains in one uniform state of composition in spite of the changes
going on at the surface of the earth. Omitting the aqueous vapour, or steam, ever
present in variable quantities in the atmosphere, ten thousand volumes of dry air
contain, according to Graham:—

Nitrogen 7912
Oxygen 2080
Carbonic acid 4
Carburetted hydrogen (CH2) 4
Ammonia a trace
——————
10,000

Fig. 108.
a. Gas jar containing nitrogen, n, standing on b, another jar full of oxygen, o. The taper, c,
is extinguished at n, and relighted at o. d d. Stand supporting the jars.

Fourth Experiment.

It was the elegant, the accomplished, but ill-fated Lavoisier who discovered, by
experimenting with quicksilver and air, the compound nature of the atmosphere;
and it was the same chemist who gave the name of azote to nitrogen; it should,
however, be borne in mind that it does not necessarily follow because a gas
extinguishes flame that it is a poison. Nitrogen extinguishes flame, but we inhale
enormous quantities of air without any ill effects from the nitrogen or azote that
it contains; on the other hand, many gases that extinguish flame are specific
poisons, such as carbonic acid, carbonic oxide, cyanogen, &c.
Lavoisier's experiment may be repeated by passing into a measured jar,
graduated into five equal volumes, four measures of nitrogen and one measure
of oxygen; a glass plate should then be slid over the mouth of the vessel, and it
may be turned up and down gently for some little time to mix the two gases, and
when the mixture is tested with a lighted taper, it is found neither to increase nor

diminish the illuminating power and the taper burns as it would do in
atmospheric air. (Fig. 109.)

Fig. 109.
a. Gas jar divided into five equal parts. b B. Section of pneumatic trough, to show the
decantation of gas from one vessel to another. The gas is being passed from c to a, through
the water.

HYDROGEN.

Hydrogen (υδωρ, water; γενναω, I give rise to), so termed by Lavoisier—called
by other chemists inflammable air, and phlogiston. Symbol, H; combining
properties, 1. The lightest known form of matter.
Every 100 parts by weight of water contain 11 parts of hydrogen gas; and as the
quantity of water on the surface of the earth represents at least two-thirds of the
whole area, the source of this gas, like that of oxygen or nitrogen, is
inexhaustible. Van Helmont, Mayow, and Hales had shown that certain
inflammable and peculiar gases could be obtained, but it was reserved for the
rigidly philosophic mind of Cavendish to determine the nature of the elements
contained in, and giving a speciality to, the inflammable gases of the older
chemists. By acting with dilute acids upon iron, zinc, and tin, Cavendish
liberated an inflammable elastic gas; and he discovered nearly all the properties
we shall notice in the succeeding experiments, and especially demonstrated the
composition of water in his paper read before the Royal Society in the year
1784.

First Experiment.

Hydrogen is prepared in a very simple manner, by placing some zinc cuttings in
a bottle, to which is attached a cork and pewter or bent glass tube, and pouring
upon the metal some dilute sulphuric or hydrochloric acid. Effervescence and
ebullition take place, and the gas escapes in large quantities, water being
decomposed; the oxygen passes to the zinc, and forms oxide of zinc, and this
uniting with the sulphuric acid forms sulphate of zinc, which may be obtained
after the escape of the hydrogen by evaporation and crystallization. (Fig. 110.)
Zn + HO.SO3 = ZnO.SO3 + H;
or,
Zn + HCl = ZnCl + H.
In nearly all the processes employed for the generation of hydrogen gas, a metal
is usually employed, and this fact has suggested the notion that hydrogen may
possibly be a metal, although it is the lightest known form of matter; and it will
be observed in all the succeeding experiments that a metallic substance will be
employed to take away the oxygen and displace the hydrogen.

Fig. 110.
a. Bottle containing zinc cuttings and water and fitted with a cap and two tubes, the one
marked b, containing a funnel, conveys the sulphuric acid to the zinc and water, whilst the
gas escapes through the pipe c.

Whenever hydrogen is prepared it should be allowed to escape from the
generating vessel for a few minutes before any flame is applied, in order that the

atmospheric air may be expelled. The most serious accidents have occurred from
carelessness in this respect, as a mixture of hydrogen and air is explosive, and
the more dangerous when it takes fire in any closed glass bottle.

Second Experiment.

If a piece of potassium is confined in a little coarse wire gauze cage, attached to
a rod, and thrust under a small jar full of water, placed on the shelf of the
pneumatic trough, hydrogen gas is produced with great rapidity, and is received
into the gas jar. The bit of potassium being surrounded with water, is kept cool,
whilst the hydrogen escaping under the water is not of course burnt away, as it is
whenever the metal is thrown on the surface of water.

Third Experiment.

Across a small iron table-furnace is placed about eighteen inches of 1-inch gas-
pipe containing iron borings, the whole being red-hot; and attached to one end is
a pipe conveying steam from a boiler, or flask, or retort, whilst another pipe is
fitted to the opposite end, and passes to the pneumatic trough. Directly the steam
passes over the red hot iron borings it is deprived of oxygen, which remains with
the iron, forming the rust or oxide of iron, whilst the hydrogen, called in this
case water gas, escapes with great rapidity. When steam is passed over red-hot
charcoal, hydrogen is also produced with carbonic oxide gas, and this in fact is
the ordinary process of making water gas, which being purified is afterwards
saturated with some volatile hydrocarbon and burnt. At first sight, such a mode
of making gas would be thought extremely profitable, and in spite of the
numerous failures the discovery (so called) of water gas is reproduced as a sort
of chronic wonder; but experience and practice have clearly demonstrated that
water gas is a fallacy, and as long as we can get coal it is not worth while going
through the round-about processes of first burning coal to produce steam;
secondly, of burning coal to heat charcoal, over which the steam is passed to be
converted into gas, which has then to be purified and saturated with a cheap
hydrocarbon obtained from coal or mineral naphtha; whilst ordinary coal gas is
obtained at once by heating coal in iron retorts. (Fig. 111.)
Thus, by the metals zinc, tin, potassium, red-hot iron (and we might add several
others), the oxygen of water is removed and hydrogen gas liberated.

Fig. 111.
a. Flask containing water, and producing steam, which passes to the iron tube, b b,
containing the iron borings heated red hot in the charcoal stove c. The hydrogen passes to
the jar d, standing on the shelf of the pneumatic trough.

Fourth Experiment.

If bottles of hydrogen gas are prepared by all the processes described, they will
present the same properties when tested under similar circumstances. A lighted
taper applied to the mouths of the bottles of hydrogen, which should be inverted,
causes the gas to take fire with a slight noise, in consequence of the mixture of
air and hydrogen that invariably takes place when the stopper is removed; on
thrusting the lighted taper into the bulk of the gas it is extinguished, showing
that hydrogen possesses the opposite quality to oxygen—viz., that it takes fire,
but does not support combustion. By keeping the bottles containing the
hydrogen upright, when the stopper is removed the gas escapes with great
rapidity, and atmospheric air takes its place, so much so that by the time a
lighted taper is applied, instead of the gas burning quietly, it frequently
astonishes the operator with a loud pop. This sudden attack on the nerves may be
prevented by always experimenting with inverted bottles. (Fig. 112.)

Fig. 112.
a. Bottle opened upright, and hydrogen exploding. b. Bottle opened inverted, and hydrogen
burning quietly at the mouth.

Fifth Experiment.

Hydrogen is 14.4 lighter than air, and for that reason may be passed into bottles
and jars without the assistance of the pneumatic trough. One of the most
amusing proofs of its levity is that of filling paper bags or balloons with this gas;
and we read, in the accounts of the fêtes at Paris, of the use of balloons
ingeniously constructed to represent animals, so that a regular aerial hunt was
exhibited, with this drawback only, that nearly all the animals preferred
ascending with their legs upwards, a circumstance which provoked intense mirth
amongst the volatile Frenchmen. The lightness of hydrogen may be shown in
two ways—first, by filling a little gold-beater's skin balloon with pure hydrogen
(prepared by passing the gas made from zinc and dilute pure sulphuric acid
through a strong solution of potash, and afterwards through one of nitrate of
silver), and allowing the balloon to ascend; and then afterwards, having of
course secured the balloon by a thin twine or strong thread, it may be pulled
down and the gas inhaled, when a most curious effect is produced on the voice,
which is suddenly changed from a manly bass to a ludicrous nasal squeaking
sound. The only precautions necessary are to make the gas quite pure, and to
avoid flame whilst inhaling the gas. It is related by Chaptal that the intrepid

(quære, foolish) but unfortunate aeronaut, Mons. Pilate de Rosio, having on one
occasion inhaled hydrogen gas, was rash enough to approach a lighted candle,
when an explosion took place in his mouth, which he says "was so violent that
he fancied all his teeth were driven out." Of course, if it were possible to change
by some extraordinary power the condition of the atmosphere in a concert-room
or theatre, all the bass voices would become extremely nasal and highly comic,
whilst the sopranos would emulate railway whistles and screech fearfully; and
supposing the specific gravity of the air was continually and materially
changing, our voices would never be the same, but alter day by day, according to
the state of the air, so that the "familiar voice" would be an impossibility.
A bell rung in a gas jar containing air emits a very different sound from that
which is produced in one full of hydrogen—a simple experiment is easily
performed by passing a jar containing hydrogen over a self-acting bell, such as is
used for telegraphic purposes. (Fig. 113.)

Fig. 113.
a. Stand and bell. b b. Tin cylinder full of hydrogen, which may be raised or depressed at
pleasure, by lifting it with the knob at the top, when the curious changes in the sound of the
bell are audible.

Sixth Experiment.

Some of the small pipes from an organ may be made to emit the most curious
sounds by passing heavy and light gases through them; in these experiments
bags containing the gases should be employed, which may drive air, oxygen,
carbonic acid, or hydrogen, through the organ pipes at precisely the same
pressure.

Seventh Experiment.

One of those toys called "The Squeaking Toy" affords another and ridiculous
example of the effect of hydrogen on sound, when it is used in a jar containing
this gas. (Fig. 114.)

Fig. 114.
The squeaking toy, used in a jar of hydrogen.

Eighth Experiment.

An accordion played in a large receptacle containing hydrogen gas demonstrates
still more clearly what would be the effect of an orchestra shut up in a room
containing a mixture of a considerable portion of hydrogen with air, as the
former, like nitrogen, is not a poison, and only kills in the absence of oxygen
gas.

Ninth Experiment.

Some very amusing experiments with balloons have been devised by Mr. Darby,
the eminent firework manufacturer, by which they are made to carry signals of
three kinds, and thus the motive or ascending power may be utilized to a certain
extent.
Mr. Darby's attention was first directed to the manufacture of a good,
serviceable, and cheap balloon, which he made of paper, cut with mathematical
precision; the gores or divisions being made equal, and when pasted together,
strengthened by the insertion of a string at the juncture; so that the skeleton of
the balloon was made of string, the whole terminating in the neck, which was
further stiffened with calico, and completed when required by a good coating of
boiled oil. These balloons are about nine feet high and five feet in diameter in
the widest part, exactly like a pear, and tapering to the neck in the most graceful
and elegant manner. They retain the hydrogen gas remarkably well for many
hours, and do not leak, in consequence of the paper of which they are made
being well selected and all holes stopped, and also from the circumstance of the
pressure being so well distributed over the interior by the almost mathematical
precision with which they are cut, and the careful preparation of the paper with
proper varnish. One of their greatest recommendations is cheapness; for whilst a
gold-beater's skin balloon of the same size would cost about 5l., these can be
furnished at 5s. each in large quantities.
A balloon required to carry one or more persons must be constructed of the best
materials, and cannot be too carefully made; it is therefore a somewhat costly
affair, and as much as 200l., 500l., and even 1000l. have been expended in the
construction of these aerial chariots.
The chief points requiring attention are:—first, the quality of the silk; secondly,
the precision and scrupulous nicety required in cutting out and joining the gores;
thirdly, the application of a good varnish to fill up the pores of the silk, which
must be insoluble in water, and sufficiently elastic not to crack.
The usual material is Indian silk (termed Corah silk), at from 2s. to 2s. 6d. per
yard.
The gores or parts with which the balloon is constructed require, as before
stated, great attention; it being a common saying amongst aeronauts, "that a
cobweb will hold the gas if properly shaped" the object being to diffuse the
pressure equally over the whole bag or balloon.

The varnish with which the silk is rendered air-tight can be made according to
the private recipe of Mr. Graham, an aeronaut, who states that he uses for this
purpose two gallons of linseed oil (boiled), two ditto (raw), and four ounces of
beeswax; the whole being simmered together for one hour, answers remarkably
well, and the varnish is tough and not liable to crack.
For repairing holes in a balloon, Mr. Graham recommends a cement composed
of two pounds of black resin and one pound of tallow, melted together, and
applied on pieces of varnished silk to the apertures.
The actual cost of a balloon will be understood from information also derived
from Mr. Graham. His celebrated "Victoria Balloon," which has passed through
so many hairbreadth escapes, was sixty-five feet high, and thirty-eight feet in
diameter in the broadest part; and the following articles were used in its
construction:—

£ s. d.
1400 yards of Corah silk, at 2s. 6d. per yard 175 0 0
The netting weighed 70 lbs. 20 0 0
Extra ropes weighed 20 lbs. at 2s. per lb. 2 0 0
The car weighed 25 lbs. 7 0 0
Varnish, wages, &c. 16 0 0
————————————
£220 0 0

Thirty-eight thousand cubic feet of coal gas were required to fill this balloon,
charged by one company 20l., by others from 9l. to 10l.; and eight men were
required to hold the inflated baggy monster.
Such a balloon as described above is a mere soap bubble when compared with
the "New Aerial Ship" now building in the vicinity of New York; the details are
so practical and interesting, that we quote nearly the whole account of this
mammoth or Great Eastern amongst balloons, as given in the New York Times.
"An experiment in scientific ballooning, greater than has yet been undertaken, is
about to be tried in this city. The project of crossing the Atlantic Ocean with an
air-ship, long talked of, but never accomplished, has taken a shape so definite
that the apparatus is already prepared and the aeronaut ready to undertake his
task.

"The work has been conducted quietly, in the immediate vicinity of New York,
since the opening of spring. The new air-ship, which has been christened the
City of New York, is so nearly completed, that but few essentials of detail are
wanting to enable the projectors to bring it visibly before the public.
"The aeronaut in charge is Mr. T. S. C. Lowe, a New Hampshire man, who has
made thirty-six balloon ascensions.
"The dimensions of the City of New York so far exceed those of any balloon
previously constructed, that the bare fact of its existence is notable. Briefly, for
so large a subject, the following are the dimensions:—Greatest diameter, 130
feet; transverse diameter, 104 feet; height, from valve to boat, 350 feet; weight,
with outfit, 3½ tons; lifting power (aggregate), 22½ tons; capacity of gas
envelope, 725,000 cubic feet.
"The City of New York, therefore, is nearly five times larger than the largest
balloon ever before built. Its form is that of the usual perpendicular gas-receiver,
with basket and lifeboat attached.
"Six thousand yards of twilled cloth have been used in the construction of the
envelope. Reduced to feet, the actual measurement of this material is 54,000 feet
—or nearly 11 miles. Seventeen of Wheeler and Wilson's sewing machines have
been employed to connect the pieces, and the upper extremity of the envelope,
intended to receive the gas-valve, is of triple thickness, strengthened with heavy
brown linen, and sewed in triple seams. The pressure being greatest at this point,
extraordinary power of resistance is requisite. It is asserted that 100 women,
sewing constantly for two years, could not have accomplished this work, which
measures by miles. The material is stout and the stitching stouter.
"The varnish applied to this envelope is a composition the secret of which rests
with Mr. Lowe. Three or four coatings are applied, in order to prevent leakage of
the gas.
"The netting which surrounds the envelope is a stout cord, manufactured from
flax expressly for the purpose. Its aggregate strength is equal to a resistance of
160 tons, each cord being capable of sustaining a weight of 400 lbs. or 500 lbs.
"The basket which is to be suspended immediately below the balloon is made of
rattan, is 20 feet in circumference and 4 feet deep. Its form is circular, and it is
surrounded by canvas. This car will carry the aeronauts. It is warmed by a lime-
stove, an invention of Mr. O. A. Gager, by whom it was presented to Mr. Lowe.
A lime-stove is a new feature in air voyages. It is claimed that it will furnish heat

without fire, and is intended for a warming apparatus only. The stove is 1½ feet
high, and 2 feet square. Mr. Lowe states that he is so well convinced of the
utility of this contrivance, that he conceives it to be possible to ascend to a
region where water will freeze, and yet keep himself from freezing. This is to be
tested.
"Dropping below the basket is a metallic lifeboat, in which is placed an Ericsson
engine. Captain Ericsson's invention is therefore to be tried in mid-air. Its
particular purpose is the control of a propeller, rigged upon the principle of the
screw, by which it is proposed to obtain a regulating power. The application of
the mechanical power is ingeniously devised. The propeller is fixed in the bow
of the lifeboat, projecting at an angle of about forty-five degrees. From a wheel
at the extremity twenty fans radiate. Each of these fans is 5 feet in length,
widening gradually from the point of contact with the screw to the extremity,
where the width of each is 1½ feet. Mr. Lowe claims that by the application of
these mechanical contrivances his air-ship can be readily raised or lowered, to
seek different currents of air; that they will give him ample steerage way, and
that they will prevent the rotatory motion of the machine. In applying the
principle of the fan, he does not claim any new discovery, but simply a practical
development of the theory advanced by other aeronauts, and partially reduced to
practice by Charles Green, the celebrated English aeronaut.
"Mr. Lowe contends that the application of machinery to aerial navigation has
been long enough a mere theory. He proposes to reduce the theory to practice,
and see what will come of it. It is estimated that the raising and lowering power
of the machinery will be equal to a weight of 300 lbs., the fans being so adjusted
as to admit of very rapid motion upward or downward. As the loss of three or
four pounds only is sufficient to enable a balloon to rise rapidly, and as the
escape of a very small portion of the gas suffices to reduce its altitude, Mr. Lowe
regards this systematic regulator as quite sufficient to enable him to control his
movements and to keep at any altitude he desires. It is his intention to ascend to
a height of three or four miles at the start, but this altitude will not be
permanently sustained. He prefers, he says, to keep within a respectable distance
of mundane things, where 'he can see folks.' It is to be hoped his machinery will
perform all that he anticipates from it. It is a novel affair throughout, and a
variety of new applications remain to be tested. Mr. Lowe, expressing the utmost
confidence in all the appointments of his apparatus, assured us that he would
certainly go, and, as certainly, would go into the ocean, or deliver a copy of
Monday's Times in London on the following Wednesday. He proposes to effect a
landing in England or France, and will take a course north of east. A due easterly

course would land him in Spain, but to that course he objects. He hopes to make
the trip from this city to London in forty-eight hours, certainly in sixty-four
hours. He scouts the idea of danger, goes about his preparations deliberately, and
promises himself a good time. As the upper currents, setting due east, will not
permit his return by the same route, he proposes to pack up the City of New
York, and take the first steamer for home.
"The air-ship will carry weight. Its cubical contents of 725,000 feet of gas
suffice to lift a weight of 22½ tons. With outfit complete its own weight will be
3½ tons. With this weight 19 tons of lifting power remain, and there is
accordingly room for as many passengers as will care to take the venture. We
understand, however, that the company is limited to eight or ten. Mr. Lowe
provides sand for ballast, regards his chances of salvation as exceedingly
favourable, places implicit faith in the strength of his netting, the power of his
machinery, and the buoyancy of his lifeboat, and altogether considers himself
secure from the hazard of disaster. If he accomplish his voyage in safety, he will
have done more than any air navigator has yet ventured to undertake. If he fail,
the enterprise sinks the snug sum of 20,000 dollars. Wealthy men who are his
backers, sharing his own enthusiasm, declare failure impossible, and invite a
patient public to wait and see."
A night ascent witnessed at any of the public gardens is certainly a stirring
scene, particularly if the wind is rather high. On approaching the balloon,
swayed to and fro by the breeze, it seems almost capable of crushing the bold
individual who would venture beneath it; seen as a large dark mass in the yet
dimly-lighted square, it appears to be incapable of control; when the inflation is
completed, the aeronaut, all importance, seats himself in the car, and blue lights,
with other fireworks, display the victim who is to make a "last ascent," or
perhaps descent. Finally the word is given, the ropes are cast off, and the bulky
chariot rises majestically to the sound of the National Anthem. The crowd see no
more, but the next day's Times reports the end of the aerial journey.
Balloons can never be of any permanent value as means of locomotion until they
can be steered; and this is a problem, the solution of which is something like
perpetual motion. In the first place, a balloon of any size exposes an enormous
surface to the pressure and force of the winds; and when we consider that they
move at the rate of from three to eighty miles per hour, it will be understood that
the fabric of the balloon itself must give way in any attempt to tear, work, or pull
it against such a force. Secondly and lastly, the power has not yet been created
which will do all this without the inconvenience of being so heavy that the

steering engine fixes the balloon steadily to the earth by its obstinate gravity.
When engines of power are constructed without the aeronaut's obstacle of
weight—when balloons are made of thin copper or sheet-iron, then we may
possibly hear of the voyage of the good ship Aerial, bound for any place, and
quite independent of dock, port, and the host of dues (quere), which the sea-
going ships have to disburse. It is, however, gratifying to the zeal and
perseverance of those who dream of aerial navigation, to know that a balloon is
not quite useless; and here we may return to the consideration of Mr. Darby's
signals, which are of various kinds, and intended to appeal to the senses by night
as well as by day; and first, by audible sounds. Such means have long been
recognised, from the ancient float and bell of the "Inchcape Rock," to the painful
minute-gun at sea, or the shrill railway whistle and detonating signals employed
to prevent the horrors of a collision between two trains. The signal sounds are
produced by the explosion of shells capable of yielding a report equal to that of a
six-pounder cannon, and they are constructed in a very simple manner. A ball,
composed of wood or copper, and made up by screwing together the two
hemispheres, is attached to a shaft or tail of cane or lance-wood, properly
feathered like an arrow; at the side opposite to that of the arrow—viz., at its
antipodes, is placed a slight protuberance containing a minute bulb of glass filled
with oil of vitriol, and surrounded with a mixture of chlorate of potash and
sugar, the whole being protected with gutta-percha, and communicating by a
touch-hole with the interior, which is of course filled with gunpowder. These
shells are attached to a circular framework by a strong whipcord, which passes
to a central fuse, and are detached one after the other as the slow fuse (made
hollow on the principle of the argand lamp) burns steadily away. Directly a shell
falls to the ground, the little bulb containing the oil of vitriol breaks, and the acid
coming in contact with the chlorate of potash and sugar, causes the mixture to
take fire, when the gunpowder explodes. During the siege of Sebastopol many
similar mines were prepared by the Russians in the earth, so that when an
unfortunate soldier trod upon the spot, the concealed mine blew up and seriously
injured him; such petty warfare is as bad as shooting sentries, and a cruel
application of science, that unnecessarily increases the miseries of war without
producing those grand results for which the truly great captains, Wellington and
Napoleon, only warred. (Fig. 115.)

Fig. 115.
a. Ring attached to balloon, carrying an hexagonal framework with six shells. b. Hollow
fuse, which burns slowly up to the strings, and detaches each shell in succession. c. Section
of shell. The shaded portion represents the gunpowder.

The bill distributor consists of a long piece of wood, to which are attached a
number of hollow fuses, with packets of bills, protected from being burned or
singed by a thin tin plate; 10,000 or 20,000 bills can thus be delivered, and the
wind assists in scattering them, whilst the balloon travels over a distance of
many miles. It must be recollected that in each case the shells and the bills are
detached by the string burning away as the fire creeps up from the fuse. (Fig.
116.)

Fig. 116.
The bill distributor, consisting of three hollow fuses, with bills attached in packets.

Another most ingenious arrangement, also prepared by Mr. Darby, is termed by
the inventor, the "Land and Water Signal," and may be thus described:—A short
hollow ball of gutta-percha, or other convenient material, five or six inches in
diameter, and filled with printed bills, or the information, whatever it may be,
that is required to be sent, is attached to a cap to which a red flag, having the
words "Open the shell" and four cross sticks, canes, or whalebones with bits of
cork at equal distances, are fitted. The whole is connected by a string to the fuse
as before described. These signals are adapted for land and water: in either case
they fall upright, and in consequence of the sticks projecting out they float well
in the water, and can be seen by a telescope at a distance of three miles. (Fig.
117.) Many of these signals were sent away by Mr. Darby from Vauxhall; one
was picked up at Harwich, another at Brighton, a third at Croydon; in the latter
case it was found by a cottager, who, fearing gunpowder and combustibles, did
not examine the shell, but having mentioned the circumstance to a gentleman
living near him, they agreed to cut it open; and intelligence of their arrival, in
this and the other cases, was politely forwarded to Mr. Darby at Vauxhall
Gardens.

Fig. 117.

The land and water signal, which remains upright on land, or floats on the surface of water.
a. The water-tight gutta-percha shell, containing the message or information. b b b. Sticks
of cane to keep the flag in an upright position; at the ends are attached cork bungs.

Balloons, like a great many other clever inventions, have been despised by
military men as new-fangled expedients, toys, which may do very well to please
the gaping public, but are and must be useless in the field. Over and over again it
has been suggested that a balloon corps for observation should be attached to the
British army, but the scheme has been rejected, although the expense of a few
yards of silk and the generation of hydrogen gas would be a mere bagatelle as
compared with the transport and use of a single 32-pounder cannon. The
antiquated notions of octogenarian generals have, however, received a great
shock in the fact that the Emperor Napoleon III. was enabled, by the assistance
of a captive balloon, to watch the movements and dispositions of the Austrian
troops; and with the aid of the information so obtained, he made his
preparations, and was rewarded by the victory of Solferino; and as soon as the
battle was over Napoleon III. occupied at Cavriana the very room and ate the
dinner prepared for his adversary, the Emperor Francis Joseph.
Over and over again the most excellent histories have been written of
aerostation, but they all tend to one truth, and that is, the great danger and risk of
such excursions; and to enable our readers to form their own judgment, a
chronological list of some of the most celebrated aeronauts, &c., is appended.
1675. Bernair attempted to fly—killed.
1678. Besnier attempted to fly.
1772. L'Abbé Desforges announced an aerial chariot.
1783. Montgolfier constructed the first air balloon.
" Roberts frères, first gas balloon, destroyed by the peasantry of
Geneva, who imagined it to be an evil spirit or the moon.
1784. Madame Thiblé, the first lady who was ever up in the clouds;
she ascended 13,500 feet.
" Duke de Chartres, afterwards Egalité Orleans, travelled 135
miles in five hours in a balloon.
" Testu de Brissy, equestrian ascent.
" D'Achille, Desgranges, and Chalfour—Montgolfier balloon.
" Bacqueville attempted a flight with wings.
" Lunardi—gas balloon.
" Rambaud—Montgolfier balloon, which was burnt.
" Andreani—Montgolfier balloon.
1785. General Money—gas balloon, fell into the water, and not rescued

for six hours.
" Thompson, in crossing the Irish Channel, was run into with the
bowsprit of a ship whilst going at the rate of twenty miles
per hour.
" Brioschi—gas balloon ascended too high and burst the balloon;
the hurt he received ultimately caused his death.
" A Venetian nobleman and his wife—gas balloon—killed.
" Pilatre de Rozier and M. Romain—gas balloon took fire—both
killed.
1806. Mosment—gas balloon—killed.
" Olivari—Montgolfier balloon—killed.
1808. Degher attempted a flight with wings.
1812. Bittorf—Montgolfier balloon—killed.
1819. Blanchard, Madame—gas balloon—killed.
1819. Gay Lussac—gas balloon, ascended 23,040 feet above the level of
the sea. Barometer 12.95 inches; thermometer 14.9 Fah.
" Gay Lussac and Biot—gas balloon for the benefit of science.
Both philosophers returned safely to the earth.
1824. Sadler—gas balloon—killed.
" Sheldon—gas balloon.
" Harris—gas balloon—killed.
1836. Cocking—parachute from gas balloon—killed.
1847. Godard—Montgolfier balloon fell into and extricated from the
Seine.
1850. Poitevin, a successful French aeronaut.
" Gale, Lieut.—gas balloon—killed.
" Bixio and Barral—gas balloon.
" Graham, Mr. and Mrs.—gas balloon.—Serious accident ascending
near the Great Exhibition in Hyde Park.
" Green, the most successful living aeronaut of the present time.
Of the 41 persons enumerated, 14 were killed, and nearly all the aeronauts met
with accidents which might have proved fatal.

Fig. 118.
Flying machine (theoretical).

Tenth Experiment.

Soap bubbles blown with hydrogen gas ascend with great rapidity, and break
against the ceiling; if interrupted in their course with a lighted taper they burn
with a slight yellow colour and dull report.

Eleventh Experiment.

By constructing a pewter mould in two halves, of the shape of a tolerably large
flask, a balloon of collodion may be made by pouring the collodion inside the
pewter vessel, and taking care that every part is properly covered; the pewter
mould may be warmed by the external application of hot water, so as to drive off
the ether of the collodion, and when quite dry the mould is opened and the
balloon taken out. Such balloons may be made and inflated with hydrogen by
attaching to them a strip of paper, dipped in a solution of wax and phosphorus,
and sulphuret of carbon; as the latter evaporates, the phosphorus takes fire and
spreads to the balloon; which burns with a slight report. The pewter mould must
be very perfectly made, and should be bright inside; and if the balloons are filled
with oxygen and hydrogen, allowing a sufficient excess of the latter to give an

ascending power, they explode with a loud noise directly the fire reaches the
mixed gases.

Twelfth Experiment.

In a soup-plate place some strong soap and water; then blow out a number of
bubbles with a mixture of oxygen and hydrogen; a loud report occurs on the
application of flame, and if the room is small the window should be placed open,
as the concussion of the air is likely to break the glass.

Thirteenth Experiment.

Any noise repeated at least thirty-two times in a second produces a musical
sound, and by producing a number of small explosions of hydrogen gas inside
glass tubes of various sizes, the most peculiar sounds are obtained. The
hydrogen flame should be extremely small, and the glass tubes held over it may
be of all lengths and diameters; a trial only will determine whether they are fit
for the purpose or not.

Fourteenth Experiment.

Flowers, figures, or other designs, may be drawn upon silk with a solution of
nitrate of silver, and the whole being moistened with water, is exposed to the
action of hydrogen gas, which removes the oxygen from the silver, and reduces
it to the metallic state.
In like manner designs drawn with a solution of chloride of gold are produced in
the metallic state by exposure to the action of hydrogen gas. Chloride of tin,
usually termed muriate of tin, may also be reduced in a similar manner, care
being taken in these experiments that the fabric upon which the letters, figures,
or designs are painted with the metallic solution be kept quite damp whilst
exposed to the hydrogen gas.

Fifteenth Experiment.

A mixture of two volumes of hydrogen with one volume of oxygen explodes
with great violence, and produces two volumes of steam, which condense
against the sides of the strong glass vessel, in which the experiment may be

made, in the form of water. As the apparatus called the Cavendish bottle, by
which this experiment only may be safely performed, is somewhat expensive,
and requires the use of an air-pump, gas jars with stop-cocks, and an electrical
machine and Leyden jar, other and more simple means may be adopted to show
the combination of oxygen and hydrogen, and formation of water.
If a little alcohol is placed in a cup and set on fire, whilst an empty cold gas jar is
held over the flame, an abundant deposition of moisture takes place from the
combustion of the hydrogen of the spirits of wine. Alcohol contains six
combining properties of hydrogen, with four of charcoal and two of oxygen. If a
lighted candle, or an oil, camphine, Belmontine, or gas flame, is placed under a
proper condenser, large quantities of water are obtained by the combustion of
these substances (Fig. 119).

Fig. 119.
a. A burning candle, or oil or gas lamp. Copper head and long pipe fitting into b c, the
receiver from which the condensed water drops into d. e e. Two corks fitted, between
which is folded some wet rag.

Sixteenth Experiment.

During the combustion of a mixture of two volumes of hydrogen with one of
oxygen, an enormous amount of heat is produced, which is usefully applied in
the arrangement of the oxy-hydrogen blowpipe. The flame of the mixed gases
produces little or no light, but when directed on various metals contained in a
small hole made in a fire brick, a most intense light is obtained from the
combustion of the metals, which is variously coloured, according to the nature
of the substances employed. With cast-iron the most vivid scintillations are
obtained, particularly if after having fused and boiled the cast-iron with the jet of
the two gases, one of them, viz., the hydrogen, is turned off, and the oxygen only
directed upon the fused ball of iron, then the carbon of the iron burns with great
rapidity, the little globule is enveloped in a shower of sparks, and the whole
affords an excellent notion of the principle of Bessemer's patent method of
converting cast-iron at once into pure malleable iron, or by stopping short of the
full combustion of carbon, into cast-steel.
The apparatus for conducting these experiments is of various kinds, and different
jets have been from time to time recommended on account of their alleged
safety. It may be asserted that all arrangements proposed for burning any
quantity of the mixed gases are extremely dangerous: if an explosion takes place
it is almost as destructive as gunpowder, and should no particular damage be
done to the room, there is still the risk of the sudden vibration of the air
producing permanent deafness. If it is desired to burn the mixed gases, perhaps
the safest apparatus is that of Gurney; in this arrangement the mixed gases
bubble up through a little reservoir of water, and thus the gas-holder—viz., a
bladder, is cut off from the jet when the combustion takes place. (Fig. 120.) This
jet is much recommended by Mr. Woodward, the highly respected President of
the Islington Literary and Scientific Institution, and may be fitted up to show the
phenomena of polarized light, the microscope, and other interesting optical
phenomena.

Fig. 120.
Gurney's jet. a. Pipe with stop-cock leading from the gas-holder. b. The little reservoir of
water through which the mixed gases bubble. c. The jet where the gases burn. d. Cork,
which is blown out if the flame recedes in the pipe, c.

Mr. Woodward states, that a series of experiments, continued during many years,
has proved, that while the bladder containing the mixed gases is under pressure,
the flame cannot be made to pass the safety chambers, and consequently an
explosion is impossible; and even if through extreme carelessness or design, as
by the removal of pressure or the contact of a spark with the bladder, an
explosion occurs, it can produce no other than the momentary effect of the alarm
occasioned by the report; whereas, when the gases are used in separate bags
under a pressure of two or three half hundredweights, if the pressure on one of
the bags be accidentally removed or suspended, the gas from the other will be
forced into it, and if not discovered in time, will occasion an explosion of a very
dangerous character; or if through carelessness one of the partially emptied bags
should be filled up with the wrong gas, effects of an equally perilous nature
would ensue.

Fig. 121.
a. The bladder of mixed gases, pressed by the board, b b, attached by wire supports to
another board, c c, which carries the weights, d d. e e. Pipe to which the bladder, a, is
screwed, and when a is emptied, it is re-filled from the other bladder, r. f f f. Pipe
conveying mixed gases to the lantern, g g, where they are burnt from a Gurney's jet, h.

In the oxy-hydrogen blowpipe usually employed, the gases are kept quite
separate, either in gasometers or gas bags, and are conveyed by distinct pipes to
a jet of very simple construction, devised by the late Professor Daniell, where
they mix in very small volumes, and are burnt at once at the mouth of the jet.
(Fig. 122.)

Fig. 122.

Daniell's jet. o o. The stop-cock and pipe conveying oxygen, and fitting inside the larger
tube h h, to which is attached a stop-cock, h, connected with the hydrogen receiver. a. The
orifice near which the gases mix, and where they are burnt.

The gases are stored either in copper gasometers or in air-tight bags of
Macintosh cloth, capable of containing from four to six cubic feet of gas, and
provided with pressure boards. The boards are loaded with two or three fifty-six
pound weights to force out the gas with sufficient pressure, and of course must
be equally weighted; if any change of weight is made, the stop-cocks should be
turned off and the light put out, as the most disastrous results have occurred
from carelessness in this respect. (Fig. 123.)

Fig. 123.
Fig. 123. Gas bag and pressure boards.

The oxy-hydrogen jet is further varied in construction by receiving the gases
from separate reservoirs, and allowing them to mix in the upper part of the jet,
which is provided with a safety tube filled with circular pieces of wire gauze.
(Fig. 124.) With this arrangement a most intense light is produced, called the
Drummond or lime light, and coal gas is now usually substituted for hydrogen.

Fig. 124.
a a. Board to which b b is fixed. o. Oxygen pipe. h. Hydrogen pipe. c c. Space filled with
wire gauze. d. Lime cylinder.

Seventeenth Experiment.

There are many circumstances that will cause the union of oxygen and
hydrogen, which, if confined by themselves in a glass vessel, may be preserved
for any length of time without change; but if some powdered glass, or any other
finely-divided substance with sharp points, is introduced into the mixed gases at
a temperature not exceeding 660° Fahrenheit, then the gases silently unite and
form water.
This curious mode of effecting their combination is shown in a still more
interesting manner by perfectly clear platinum foil, which if introduced into the
mixed gases gradually begins to glow, and becoming red-hot causes the gases to
explode. Or still better, by the method first devised by Dobereiner, in 1824, by
which finely prepared spongy platinum—i.e., platinum in a porous state, and
exposing a large metallic surface—is almost instantaneously heated red-hot by
contact with the mixed gases. When this fact became known, it was further
applied to the construction of an instantaneous light, in which hydrogen was
made to play upon a little ball of spongy platinum, and immediately kindled.

These Dobereiner lamps were possessed by a few of the curious, and would no
doubt be extensively used if the discovery of phosphorus had not supplied a
cheaper and more convenient fire-giving agent. When the spongy platinum is
mixed with some fine pipeclay, and made into little pills, they may (after being
slightly warmed) be introduced into a mixture of the two gases, and will silently
effect their union. The theory of the combination is somewhat obscure, and
perhaps the simplest one is that which supposes the platinum sponge to act as a
conductor of electric influences between the two sets of gaseous particles;
although, again, it is difficult to reconcile this theory with the fact that powdered
glass at 660°, a bad conductor of electricity, should effect the same object. The
result appears to be due to some effects of surface by which the gases seem to be
condensed and brought into a condition that enables them to abandon their
gaseous state and assume that of water.
When Sir H. Davy invented the safety-lamp, he was aware that, in certain
explosive conditions of the air in coal mines, the flame of the lamp was
extinguished, and in order that the miner should not be left in the dreary
darkness and intricacies of the galleries without some means of seeing the way
out, he devised an ingenious arrangement with thin platinum wire, which was
coiled round the flame of the lamp, and fixed properly, so that it could not be
moved from its proper place by any accidental shaking. When the flame of the
safety-lamp, having the platinum wire attached, was accidentally extinguished
by the explosive atmosphere in which it was burning, the platinum commenced
glowing with an intense heat, and continued to emit light as long as it remained
in the dangerous part of the mine. Sir H. Davy warned those who might use the
platinum to take care that no portion of the thin wire passed outside the wire
gauze, for the obvious reason that, if ignited outside the wire gauze protector, it
would inflame the fire-damp.

Eighteenth Experiment.

Water is decomposed by passing a current of voltaic electricity through it by
means of two platinum plates, which may be connected with a ten-cell Grove's
battery. The gases are collected in separate tubes, and the experiment offers one
of the most instructive illustrations of the composition of water. (Fig. 125.)

Fig. 125.
p p. Two platinum plates connected with wires to the cups. The wires are passed through
holes in the finger-glass, b b, and are fixed perfectly steady by pouring in cement composed
of resin and tallow to the line l l. Two glass tubes filled with water acidulated with
sulphuric acid, and placed over the platinum plates in finger-glass, which also contains
dilute sulphuric acid to improve the conducting power of the water. The wires of the battery
are placed in the cups, and the arrows show the direction of the current of electricity.

There is a current of electricity passing from and between two platinum plates
decomposing water, offering the converse of the Dobereiner experiment, and
highly suggestive of the probability of the theory already advanced in
explanation of the singular combination of oxygen and hydrogen in the presence
of clean platinum foil, and more especially when we consider the operation of
Grove's gas battery, in which a current of electricity is produced by pieces of
platinum foil covered with finely-divided platinum, called platinum black; each
piece is contained in a separate glass tube filled alternately with oxygen and
hydrogen, and by connecting a great number of these tubes a current of
electricity is obtained, whilst the oxygen and hydrogen are slowly absorbed and
disappear, having combined and formed water, although placed in separate glass
tubes. (Fig. 126.)

Fig. 126.
Grove's gas battery consists of tubes containing oxygen and hydrogen alternately, and
having a thin piece of platinum foil, p, inserted by the blowpipe in each glass tube. The foil
hangs down the full length of the interior of the glass. Each pair of tubes is contained in a
little glass tumbler containing some dilute sulphuric acid, and the hydrogen tube, h, of one
pair, is connected with the oxygen tube, o, of the next. w w. The terminal wires of the
series.

The analysis of water is shown very perfectly on the screen by fitting up some
very small tubes and platinum wires in the same manner as shown in fig. 125.
The vessel in which the tubes and wires are contained with the dilute sulphuric
acid must be small, and arranged so as to pass nicely into the space usually filled
by the picture in an ordinary magic lantern, or, still better, in one lighted by the
oxy-hydrogen or lime light. If the dilute acid is coloured with a little solution of
indigo, the gradual displacement of the fluid by the production of the two gases
is very perfectly developed on the screen when the small voltaic battery is
attached to the apparatus; and of course a large number of persons may watch
the experiment at the same time.
With respect to the application of the light produced from a jet of the mixed
gases thrown upon a ball of lime, it may be stated that for many years the
dissolving view lanterns and other optical effects have been produced with the
assistance of this light; and more lately Major Fitzmaurice has condensed the
mixed gases in the old-fashioned oil gas receivers, and projected them on a ball
of lime; and it was this light thrown from many similar arrangements that
illuminated the British men-of-war when Napoleon III. left her Majesty's yacht
at night in the docks at Cherbourg.

Fig. 127.
Cherbourg.

Mr. Sykes Ward, of Leeds, has also proposed a most simple and excellent
application of the oxy-hydrogen light for illumination under the surface of
water, and for the convenience of divers, who are frequently obliged to cease
their operations in consequence of the want of light. Mr. Ward's submarine lamp
consists of a series of very strong copper tubes, which are filled with the mixed
gases by means of a force-pump; and in order to prevent the lamp being
extinguished, it burns under double glass shades, which are desirable in order to
prevent the glass immediately next to the light cracking by contact with the cold
water.

Fig. 128.
a a. Tube reservoir to hold the mixed gases. b. The jet and lime ball. d. The first glass
shade, held down by a cap and screw. c. The second glass shade. e e. The handle by which
it is lowered into the water.

The author tried this lamp at Ryde, and although the coast-guards objected to the
production of a brilliant light at night, which they stated might be mistaken for a
signal and would cause some confusion amongst the war vessels in the
immediate neighbourhood, enough experiments were made, to show that the
Ward lamp would burn for a considerable time under water, and could be kept
charged with the gas by means of a process that was easily workable in the boat.
The gases were taken out mixed in gas bags, and pumped into the reservoir
when required. With a much larger reservoir greater results could be obtained;
and if nautilus diving bells are to be used in modern warfare, they will require a
powerful light to show them their prey, so that they may attach the explosives
which are to blow great holes in the men-of-war.

Fig. 129.
Submarine lamp.

CHAPTER XI.
CHLORINE, IODINE, BROMINE, FLUORINE.

The four Halogens, or Producers of Substances like Sea Salt.
Chlorine (χλωρος, green). Symbol, Cl. Combining proportion, 35.5. Specific
gravity, 2.44. Scheele termed it dephlogisticated muriatic acid; Lavoisier,
oxymuriatic acid; Davy, chlorine.
The consideration of the nature of this important element introduces to our
notice one of the most original chemists of the eighteenth century—viz., the
illustrious Scheele, who was born at Stralsund, in 1742, and in spite of every
obstacle, fighting his "battle of life" with sickness and sorrow, he succeeded in
making some of the most valuable discoveries in science, and amongst them that
of chlorine gas. It was in the examination of a mineral solid—viz., of manganese
—that Scheele made the acquaintance of a new gaseous element; and in a highly
original dissertation on manganese, in 1774, he describes the mode of procuring
what he termed dephlogisticated muriatic acid—a name which is certainly to be
regretted, from its absurd length, but a title which was strictly in accordance
with the then established theory of phlogiston; and if the latter is considered
synonymous with hydrogen, quite in accordance with our present views of the
nature of this element. Scheele discovered the leading characteristics of chlorine,
and especially its power of bleaching, which is alone sufficient to place this gas
in a high commercial position, when it is considered that all our linen used
formerly to be sent to Holland, where they had acquired great dexterity in the
ancient mode of bleaching—viz., by exposure of the fabric to atmospheric air or
the action of the damps or dews, assisted greatly by the agency of light. Some
idea may be formed of the present value of chlorine, when it is stated that the
linen goods were retained by the Dutch bleachers for nine months; and if the
spring and summer happened to be favourable, the operation was well
conducted; on the other hand, if cold and wet, the goods might be more or less
injured by continual exposure to unfavourable atmospheric changes. At the
present time, as much bleaching can be done in nine weeks as might formerly
have been conducted in the same number of months; and the whole of the
process of chlorine bleaching is carried on independent of external atmospheric

caprices, whilst the money paid for the process no longer passes to Holland, but
remains in the hands of our own diligent bleachers and manufacturers.

First Experiment.

As Scheele first indicated, chlorine is obtained by the action of the black oxide
of manganese, on "the Spirit of Salt," or hydrochloric acid; and the most
elementary and instructive experiment showing its preparation can be made in
the following manner:—

Fig. 130.
a. Flask containing the fuming hydrochloric acid, which is gently boiled by the heat of the
spirit lamp. b. Tube passing to the Wolfe's bottle, containing pumice-stone or asbestos
moistened with sulphuric acid. c. Second tube passing into a dry empty bottle, which
receives the hydrochloric acid gas.

Place in a clear Florence oil-flask, to which a cork and bent tube have been first
fitted, some strong fuming hydrochloric acid. Arrange the flask on a ring-stand,
and then pass the bent tube either to a Wolfe's bottle containing some pumice-
stone moistened with oil of vitriol, or to a glass tube containing either pumice or
asbestos wetted with the same acid. Another glass tube, bent at right angles,
passes away from the Wolfe's bottle into a receiving bottle. (Fig. 130). On the
application of heat, the hydrochloric gas is driven off from its solution in water,
and any aqueous vapour carried up is retained by the asbestos or pumice stone
wetted with oil of vitriol; the application of the latter is called drying the gas—
i.e., depriving it of all moisture; sometimes the salt called chloride of calcium is

used for the same purpose, and it must be understood by the juvenile chemist
that gases are not dried like towels, by exposure to heat, or by putting them in
bladders before the fire, as we once heard was actually recommended, but by
causing the gas charged with invisible steam to pass over some substance having
a great affinity for water. The dry hydrochloric gas falls into the bottle, and
displaces the air, being about one-fourth heavier than the latter, and gradually
overflowing from the mouth of the vessel, produces a white smoke, which is
found to be acid by litmus paper, but has no power to bleach, and is not green; it
is, in fact, a combination of one combining proportion of chlorine with one of
hydrogen, and to detach the latter, and set the chlorine free, it is necessary to
convey the hydrochloric gas to some body which has an affinity for hydrogen.
Such a substance is provided in the use of the black oxide of manganese, which
is placed either in a small flask or in a tube provided with two bulbs, and when
heated with the lamp it separates the hydrogen from the hydrochloric gas, and
forms water, which partly condenses in the second bulb. And now the gas that
escapes is no longer acid and fuming with a white smoke on contact with the air;
but is green, has a strong odour, bleaches, and is so powerful in its action on all
living tissues, that it must be carefully avoided and not inhaled; if a small
quantity is accidentally inhaled, it produces a violent fit of coughing, which lasts
a considerable time, and is only abated by inhaling the diluted vapour of
ammonia, or ether, or alcohol, and swallowing milk and other softening drinks.
(Fig. 131).

Fig. 131.
a. The flask containing the fuming hydrochloric acid, heated by spirit lamp. b. Tube
passing to Wolfe's bottle, containing the pumice-stone or asbestos wetted with oil of vitriol.
c. Second tube, which passes into a wide-mouthed small flask containing black oxide of
manganese, partly in powder and partly in lump; and the third tube conveys the chlorine to
any convenient vessel. The double bulb tube, e e, may be substituted for the flask, the oxide
of manganese being contained in the bulb m.—N.B. Any tube may be joined on to another
by a bit of india-rubber tubing, which is tied by string.

Tube a is joined to tube b by the caoutchouc pipe c, tied with packthread.

Second Experiment.

The mode of preparing chlorine, as already given, though very instructive, is
troublesome to perform; a more simple process may therefore be described:—
Pour some strong hydrochloric acid upon powdered black oxide of manganese
contained in a Florence oil-flask, taking care that the whole of the black powder
is wetted with the acid so that none of it clings to the bottom of the flask in the
dry state to cause the glass to crack on the application of heat. A cork and bent
glass tube is now attached, and conveyed to the pneumatic trough; on the
application of heat to the mixture in the flask the chlorine is evolved, and may be
collected in stoppered bottles, the first portion that escapes, although it contains
atmospheric air, should be carefully collected in order to prevent any accident
from inhaling the gas, and it will do very well to illustrate the bleaching power
of the gas, and therefore need not be wasted. The above process may be
described in symbols, all of which are easily deciphered by reference to the table
of elements, page 86.
MnO2 + 2 HCl = MnCl + 2 HO + Cl.

Third Experiment.

Another and still more expeditious mode of preparing a little chlorine, is by
placing a small beaker glass, containing half an ounce of chlorinated lime,
usually termed chloride of lime or bleaching powder, carefully at the bottom of a

deep and large beaker glass, and then, by means of a tube and funnel, conveying
to the chloride of lime some dilute oil of vitriol, composed of half acid and half
water; effervescence immediately occurs from the escape of chlorine gas, and as
it is produced it falls over the sides of the small beaker glass into the large one,
when it may be distinguished by its green colour. If a little gas be dipped out
with a very small beaker glass arranged as a bucket, and poured into a
cylindrical glass containing some dilute solution of indigo, and shaken
therewith, the colour disappears almost instantaneously; and if a piece of Dutch
metal is thrown into the beaker glass it will take fire if enough chlorine has been
generated, or some very finely-powdered antimony will demonstrate the same
result. Thus, with a few beaker glasses, some chloride of lime, sulphuric acid, a
solution of indigo, and a little Dutch metal, the chief properties of chlorine may
be displayed. (Fig. 132.)

Fig. 132.
a a. The large beaker glass. b. The small one, containing the chloride of lime. c. The tube
and funnel down which the dilute sulphuric acid is poured. d d. Sheet of paper over top of
large glass, with hole in centre to admit the tube. e. The little beaker used as a bucket.

Fourth Experiment.

Into a little platinum spoon place a small pellet of the metal sodium, and after
heating it in the flame of a spirit lamp, introduce the metal into a bottle of
chlorine, when a most intense and brilliant combustion occurs, throwing out a
vivid yellow light, and the heat is frequently so great that the bottle is cracked.
After the combustion, and when the bottle is cool, it is usually lined with a white

powder, which will be found to taste exactly the same as salt, and, in fact, is that
substance, produced by the combination of chlorine, a virulent poison, with the
metal sodium, which takes fire on contact with a small quantity of water; and
hence the use of salt for the preparation of chlorine gas when it is required on the
large scale.

Parts.
Common salt 4
Black oxide of manganese 1
Sulphuric acid 2
Water 2

Fifth Experiment.

Some Dutch metal, or powdered antimony, or a bit of phosphorus, immediately
takes fire when introduced into a bottle containing chlorine gas, forming a series
of compounds termed chlorides, and demonstrating by the evolution of heat and
light, the energetic character of chlorine, and that oxygen is not the only
supporter of combustion; chlorine gas has even, in some cases, greater chemical
power, because some time elapses before phosphorus will ignite in oxygen gas,
whilst it takes fire directly when placed in a bottle of chlorine.

Sixth Experiment.

The weight and bleaching power of chlorine are well shown by placing a
solution of indigo in a tall cylindrical glass, leaving a space at the top of about
five inches in depth. By inverting a bottle of chlorine over the mouth of the
cylindrical glass, it pours out like water, being about two and a half times
heavier than atmospheric air, and then, after placing a ground glass plate over
the top of the glass, the chlorine is recognised by its colour, whilst the bleaching
power is demonstrated immediately the gas is shaken with the indigo solution.

Seventh Experiment.

As a good contrast to the last experiment, another cylindrical jar of the same size
may be provided, containing a solution of iodide of potassium with some starch,
obtained by boiling a teaspoonful of arrowroot with some water; any chlorine
left in the bottle (sixth experiment) may be inverted into the top of this glass and

shaken, when it turns a beautiful purple blue in consequence of the liberation of
iodine by the chlorine, whose greater affinity for the base produces this result.
The colour is caused by the union of the iodine and the starch, which form
together a beautiful purple compound, and thus the apparent anomaly of
destroying and producing colour with the same agent is explained.

Eighth Experiment.

Dry chlorine does not bleach, and this fact is easily proved by taking a perfectly
dry bottle, and putting into it two or three ounces of fused chloride of calcium
broken in small lumps, then if a bottle full of chlorine is inverted over the one
containing the chloride of calcium, taking the precaution to arrange a few folds
of blotting paper with a hole in the centre on the top of the latter to catch any
water that may run out of the chlorine bottle at the moment it is inverted, the gas
will be dried by contact with the chloride of calcium, and if a piece of paper,
with the word chlorine written on it with indigo, and previously made hot and
dry, is placed in the chlorine, no change occurs, but directly the paper is
removed, dipped in water, and placed in a bottle of damp chlorine, the colour
immediately disappears. (Fig. 133.)

Fig. 133.
a a. Dry bottle, containing chloride of calcium. b. Bottle of chlorine. The arrow indicates
the gas. c c. The blotting-paper, to catch any water from the bottle, b. d. The bottle closed,

and containing the paper.

This experiment shows that chlorine is only the means to the end, and that it
decomposes water, setting free oxygen, which is supposed to exert a high
bleaching power in its nascent state, a condition which many gases are imagined
to assume just before they take the gaseous state, a sort of intermediate link
between the solid or fluid and the gaseous condition of matter. The nascent state
may possibly be that of ozone, to which we have already alluded as a powerful
bleaching agent.

Ninth Experiment.

A piece of paper dipped in oil of turpentine emits a dense black smoke, and
frequently a flash of fire is perceptible, directly it is plunged into a bottle
containing chlorine gas; here the gas combines only with the hydrogen of the
turpentine, and the carbon is deposited as soot.

Tenth Experiment.

If a lighted taper is plunged into a bottle of chlorine it continues to burn,
emitting an enormous quantity of smoke, for the reason already explained, and
demonstrating the perfection of the atmosphere in which we live and breathe,
and showing that had oxygen gas possessed the same properties as chlorine, the
combustion of compounds of hydrogen and carbon would have been impossible,
in consequence of the enormous quantity of soot which would have been
produced, so that some other element that would freely enter into combination
with it must have been provided to produce both artificial light and heat.
Chlorine is a gas which cannot be inhaled, and ozone presents the same features,
as a mouse confined for a short time with an excess of ozone soon died; but
ozone is the extraordinary condition of oxygen; the element in the ordinary state
is harmless, and is the one which enters so largely into the composition of the air
we breathe.

Eleventh Experiment.

When one volume of olefiant gas (prepared by boiling one measure of alcohol
and three of sulphuric acid) is mixed with two volumes of chlorine, and the two
gases agitated together in a long glass vessel for a few seconds, with a glass
plate over the top, which should have a welt ground perfectly flat, they unite on

the application of flame, with the production of a great cloud of black smoke,
arising from the deposited carbon, whilst a sort of roaring noise is heard during
the time that the flame passes from the top to the foot of the glass. (Fig. 134.)

Fig. 134.
Remarkable deposition of carbon during the combustion of one volume of olefiant gas with two of chlorine.

Twelfth Experiment.

Formerly Bandannah handkerchiefs were in the highest estimation, and no
gentleman's toilet was thought complete without one. The pattern was of the
simplest kind, consisting only of white spots on a red or other coloured ground.
These spots were produced in a very ingenious manner by Messrs. Monteith, of
Glasgow, by pressing together many layers of silk with leaden plates perforated
with holes; a solution of chlorine was then poured upon the upper plate, and
pressure being applied it penetrated the whole mass in the direction of the holes,
bleaching out the colour in its passage. This important commercial result may be
imitated on the small scale by placing a piece of calico dyed with Turkey red
between two thick pieces of board, each of which is perforated with a hole two
inches in diameter, and corresponding accurately when one is placed upon the
other. The pieces of board may be squeezed together in any convenient way,
either by weights, strong vulcanized india-rubber bands or screws, and when a
strong solution of chlorine gas or of chloride of lime is poured into the hole and
percolates through the cloth, the colour is removed, and the part is bleached
almost instantaneously by first wetting the calico with a little weak acid, and
then pouring on the solution of chloride of lime. On removing and washing the

folded red calico it is found to be bleached in all the places exposed to the
solution, and is now covered with white spots. (Fig. 135.)

Fig. 135.
a. Circular hole in the upper piece of wood, a similar one being perforated in the lower one.
b b. The strong india-rubber bands. The bleaching solution is poured into a.

IODINE.

Iodine (Ιωδης, violet coloured). Symbol, I; combining proportion, 127.1;
specific gravity, 4.948. Specific gravity of iodine vapour, 8.716.
In the previous chapter, devoted to the element chlorine, little or nothing has
been said of that inexhaustible storehouse of chlorine, iodine, and bromine—
viz., the boundless ocean. Some one has remarked that, as it is possible the air
may contain a little of everything capable of assuming the gaseous form, so the
ocean may hold in a state of solution a modicum of every soluble substance, in
proof of which we have lately read of some very important experiments resulting
in the separation of the metal silver from sea water, not certainly in any
profitable quantity, but quite enough to prove its presence in the ocean.
No elaborate research is necessary to ascertain the presence of chlorine, when it
is remembered that Schafhäutl has calculated, that all the oceans on the globe
contain three millions fifty-one thousand three hundred and forty-two cubic
geographical miles of salt, or about five times more than the mass of the Alps.
Now, salt contains about 60 per cent. of chlorine gas, and therefore the bleachers
can never stand still for want of it; but iodine is not so plentiful, and was
discovered by M. Courtois, of Paris, in kelp, a substance from which he prepared

carbonate of soda, or washing soda; but as this is now more cheaply prepared
from common salt, the kelp is at present required only for the iodine salts it
contains, as also for the chloride of potassium. Kelp is obtained by burning dried
sea-weeds in a shallow pit; the ashes accumulate and melt together, and this
fused mass broken into lumps forms kelp. The ocean bed no doubt has its fertile
and barren plains and mountains, and amongst the so-called "oceanic meadows"
are to be mentioned the two immense groups and bands of sea-weed called the
Sargasso Sea, which occupy altogether a space exceeding six or seven times the
area of Germany.
The iodine is contained in the largest proportion in the deep sea plants, such as
the long elastic stems of the fucus palmatus, &c. The kelp is lixiviated with
water, and after separating all the crystallizable salts, there remains behind a
dense oily-looking fluid, called "iodine ley," to which sulphuric acid is added,
and after standing a day or two the acid "ley" is placed in a large leaden retort,
and heated gently with black oxide of manganese. The chlorine being produced
very slowly, liberates the iodine, as already demonstrated in experiment seven,
p. 133, and it is collected in glass receivers.
Iodine, when quite pure and well crystallized, has a most beautiful metallic
lustre, and presents a bluish-black colour, affording an odour which reminds one
at once of the "sea smell."

First Experiment.

A few grains of iodine placed in a flask may be sublimed at a very gentle heat,
and afford a magnificent violet vapour, which can be poured out of the flask into
a warm bottle. If the bottle is cold the iodine condenses in minute and brilliant
crystals. (Fig. 136.)

Fig. 136.
a. Flask containing iodine heated by spirit lamp. b. Cold flask above to receive the vapour.
c C. Sheet of cardboard to cut off the heat from the spirit lamp.

Second Experiment.

Upon a thin slice of phosphorus place a few small particles of iodine; the heat
produced by the combination of the two elements soon causes the phosphorus to
take fire.

Third Experiment.

Heat a brick, and then throw upon it a few grains of iodine; by holding a sheet of
white paper behind, the splendid violet colour of the vapour is seen to great
advantage. It was by the discovery of iodine in the ashes of sponge—which had
long been used as a remedy for goitre, a remarkable glandular swelling—that
this element began to be used for medical purposes, and the important salt called
iodide of potassium is now used in large quantities, not only in medicine, but
likewise for that most fascinating art, which has made its way steadily, and is
now practised so extensively, under the name of photography.

THE ART OF PHOTOGRAPHY.

It was the great George Stephenson who asked the late Dean Buckland the
posing question, "Can you tell me what is the power that is driving that train?"
alluding to a train which happened to be passing at the moment. The learned
dean answered, "I suppose it is one of your big engines." "But what drives the
engine?" "Oh, very likely a canny Newcastle driver." "What do you say to the
light of the sun?" "How can that be?" asked Buckland. "It is nothing else," said
Stephenson. "It is light bottled up in the earth for tens of thousands of years;
light, absorbed by plants and vegetables, being necessary for the condensation of
carbon during the process of their growth, if it be not carbon in another form;
and now, after being buried in the earth for long ages in fields of coal, that latent
light is again brought forth and liberated, made to work—as in that locomotive
—for great human purposes."
Such was the opinion of the most original and practical man that ever reasoned
on philosophy; and could he have lived to realize the thorough adaptation and
business use of light in the art of photography, he would have said, man is only
imitating nature, and in producing photographs he must employ the same agent
which in ages past assisted to produce the coal.
In another part of this elementary work we shall have to consider the nature of
light; here, however, the chemical part only of the process of photography will
be discussed.
Many years ago (in the year 1777) Jenny Lind's most learned countryman,
Scheele, discovered that a substance termed chloride of silver, obtained by
precipitating a solution of chloride of silver with one of salt, blackened much
sooner in the violet rays than in any other part of the spectrum. He says, "Fix a
glass prism at the window, and let the refracted sunbeams fall on the floor; in
this coloured light put a paper strewed with luna cornua (horn silver or chloride
of silver), and you will observe that this horn silver grows sooner black in the
violet ray than in any of the other rays."
In 1779, Priestley directed especial attention to the action of light on plants; and
the famous Saussure, following up these and other experiments, determined that
the carbonic acid of plants was more generally decomposed into carbon and
oxygen in the blue rays of the spectrum; these facts probably suggested the bold
theory of Stephenson already alluded to. Passing by the intermediate steps of
photography, we come to the second year of the present century, and find in the
Journal of the Royal Institution a paper by Wedgwood, entitled "An Account of a
Method of Copying Paintings upon Glass, and of making Profiles, by the
Agency of Light upon Nitrate of Silver; with observations, by H. Davy." Such a

paper would lead the reader to suppose that very little remained to be effected,
and that mere details would quickly establish the art; but in this case the
experimentalists were doomed to disappointment, as, after producing their
photographs, they could not make them permanent; they had not yet discovered
the means of fixing the pictures. Nearly fourteen years elapsed, when the subject
was again taken up by Niépcè, of Chalons, with little success, so far as the fixing
was concerned; and twenty-seven years had passed away since the experiments
of Wedgwood and Davy, when, in 1829, Niépcè and Daguerre executed a deed
of co-partnership for mutually investigating the matter. These names would
suggest a rapid progress; but, strange to relate, ten years again rolled away, the
father Niépcè had in the meantime died, and a new contract was made between
the son and M. Daguerre, when, in January, 1839, the famous discovery was
made known to the world, and in July of the same year the French Government
granted a pension for life of six thousand francs to Daguerre, and four thousand
to the son of Niépcè, who had so worthily continued the experiments
commenced by his father. The triumph of the industrious French
experimentalists was not, however, to be unique; across the Channel another
patient and laborious philosopher had completed on paper precisely the same
kind of results as those obtained by Daguerre on silver plates. Mr. Fox Talbot, in
England, had immortalized himself by a discovery which was at once called the
Talbotype, and for which a patent was secured in 1841. Having thus hastily
sketched a brief history of the art, we may now proceed to the details of the
process.

First Experiment.

A photogenic drawing, so called, but now termed a positive copy, is prepared by
placing some carefully selected paper, which is free from spots or inequalities
(good paper is now made by several English manufacturers, although some
kinds of French paper, such as Cansan's, are in high repute), in a square white
hard porcelain dish containing a solution of common salt in distilled water, 109
grains of salt to the pint. The paper is steeped in this solution for ten minutes,
and then taken out and pressed in a clean wooden press, or it should be dabbed
dry on a clean flat surface with a clean piece of white calico, which may be kept
specially for this duty and not used for anything else, and it is well that all
would-be photographers should understand that neatness and cleanliness are
perfectly indispensable in conducting these processes. If a design were required
for the armorial bearings of the art of photography, it might certainly be most
fanciful, but the motto must be cleanliness and neatness, and in preparing paper

it should not be unnecessarily handled, but lifted by the corners only. The object
of dabbing the paper is to prevent the salt accumulating in large quantities in one
part of the paper and the reverse in another, and to distribute the salt equally
through the whole. The paper being now dried, is called salted paper, and is
rendered sensitive when required by laying it down on a solution of ammonio-
nitrate of silver, prepared by adding ammonia to a solution containing sixty
grains of nitrate of silver to the ounce of distilled water, until the whole of the
oxide of silver is re-dissolved, except a very small portion. A few drops of nitric
acid are also recommended to be added, and after allowing the solution to stand,
it may be poured off quite clear, and is ready for use either in the bath, or if
economy must be rigidly adhered to, the salted paper may be laid flat on a board,
and held in its place with four pins at the corners, and then just enough to wet
the surface of the paper may be run along the side of a glass spreader, and the
liquid gently drawn over the surface of the salted paper, which is allowed to dry
on a flat surface for a few minutes, and afterwards hung up by one corner to a
piece of tape stretched across the room, until quite dry, and then placed in a
blotting-book fitting into a case which completely excludes the light. Copying-
paper should be made at night, as the day is then free for all photographic
operations requiring an abundance of light. It will not keep long, and should be
used the next day.

Fig. 137.
a. The glass spreader with cork handle. b. The silver solution clinging to rod and paper by
capillary attraction. c c c C. Four pins holding down the paper on a board.—N.B. The
spreader is made of glass rod three-eighths thick.

A piece of lace, a skeleton leaf, a sharp engraving on thin paper, and above all
things, a negative photograph on glass or paper, is easily copied by placing the
prepared paper with the prepared side (carefully protected from the light)
upwards on any flat surface, such as plate glass; upon this is arranged the bit of
lace or the negative photograph with the face or picture downwards, another bit
of plate glass is then placed over it, and weights arranged at the corners; after
exposure to the sun's rays for thirty minutes, more or less (according to the
dullness or bright aspect of the day), the picture is brought into a dark room and
examined by the light of a candle or by the light from a window covered with
yellow calico, and after placing a paper weight on one corner of the lace, or
negative picture, or copying paper, it may be carefully lifted in one part, and if
the copy is sufficiently dark, is ready for fixing, but if it is faint the lifted corner
is carefully replaced, the upper glass is laid on, and the picture again exposed to
the light. Should the position of the lace or negative be changed during the
examination, re-exposure is useless, and would only produce a double and
confused picture, as it would be impossible to lay the lace or the negative
exactly in the same place again on the copying paper.
The manipulations just described are much facilitated by using a copying-frame
or press, which consists of a square wooden frame with a thick plate-glass
window; upon this are placed the negative picture and the copying paper, and the
two are brought in close contact by means of a board at the back pressed by a
hand-screw. (Fig. 138.) After the photogenic drawing or positive copy is taken, it
is fixed by being placed in a solution of hyposulphite of soda, consisting of one
fluid ounce of saturated solution to eight of water. The saturated solution of
hyposulphite of soda is conveniently kept in a large bottle for use, and in order
to improve the colour a very little chloride of gold is added to the fixing
solution, the picture must now be thoroughly washed, dried, and pressed.

Fig. 138.

The back of the copying-frame, showing the hand-screw and pressure-board. The plate
glass inside is set in the base of the frame, and is of course the part exposed to the light.

Second Experiment.

Another mode of preparing the copying paper, called albumen paper, is to take
the whites of four eggs, and four ounces of distilled water containing one
hundred and sixty grains of chloride of ammonium; these are beaten up with a
fork or a bundle of feathers, and as the froth is produced it is skimmed off by a
silver spoon into another basin, or a beaker glass, and being allowed to settle for
twelve hours it is strained through fine muslin, and is ready for use. The best
paper is floated on the surface of this liquid for three minutes, taken out, and
dried at once on a hot plate.
In floating paper one corner is first laid down, and care taken not to enclose any
air bubbles, which would prevent the fluid wetting the paper, whilst the
remainder of the paper is slowly laid upon the surface of the fluid.
The albumen paper is excited by laying it for five minutes on a solution of
nitrate of silver, seventy-two grains to the ounce of water, and when dry it will
keep for three days. This copying paper is used in the same manner as the last,
and fresh eggs only must be used in its preparation, because stale ones soon
cause the copy to change and blacken all over from the liberation of sulphur,
which unites with the silver. The colour of the copy is sometimes improved by a
solution of hot potash, and by dipping the well-washed picture, after the use of
the hyposulphite of soda, in a very dilute solution of hydrosulphuret of
ammonia.

Third Experiment.

In the Daguerreotype process, a silver plate, after being thoroughly cleaned and
polished, is exposed to the vapour of iodine, and is thus rendered so sensitive
that it may be at once exposed in the camera. In the Talbotype process, the same
principle is apparent, and paper is prepared by first covering its surface with
iodide of silver, which is afterwards rendered sensitive to the action of light by
means of an excess of nitrate of silver, as follows:—
One side of a sheet of selected Cansan's paper is first covered (by means of a
spreader) with a solution of nitrate of silver (thirty grains to the ounce of water),
hung up in a dark room and dried; it is then immersed in a solution of iodide of

potassium of five hundred grains to a pint of distilled water, for five or ten
minutes, and immediately changes to a yellow colour in consequence of the
precipitation of the yellow iodide of silver; it is then well washed with plenty of
water, and being dried, may be kept for any length of time, and is called "iodized
paper." Light has no action whatever upon it. To render the paper sensitive, three
solutions are prepared in separate bottles, and marked 1, 2, 3.
No. 1, contains a solution of nitrate of silver, fifty grains to the ounce of water.
No. 2, glacial acetic acid.
No. 3, a saturated solution of gallic acid.
With respect to No. 3, Mr. William Crookes has shown, that when a saturated
solution of gallic acid is required in large quantities, that it is better to dissolve at
once two ounces of gallic acid in six ounces of alcohol (60° over proof); to
hasten solution, the flask may be conveniently heated by immersion in hot
water; when cold it should be filtered, mixed with half a drachm of glacial acetic
acid, and preserved in a stoppered bottle for use; so prepared it will keep
unaltered for a considerable length of time. The gallic acid is not precipitated
from this solution by the addition of water; consequently, if in any case
desirable, the development of a picture may be effected with a much stronger
bath than the one usually employed. To obtain a solution of about the same
strength as a saturated aqueous solution, such as No. 3, half a drachm of the
alcoholic solution is mixed with two ounces of water; but for my particular
purpose, says Mr. Crookes, referring to the wax-paper process, "I prefer a
weaker bath, which is prepared by mixing half a drachm with ten ounces of
water." In either case it will be found necessary to add solution of nitrate of
silver in small quantities, as the developing picture seems to require it.
Returning again to the solutions marked 1, 2, 3, the numbers will assist the
memory in mixing the proportions of each. If the paper is required to be used at
once, a drachm of each may be mixed together and spread over the iodized paper
(of course, in a dark room), which is then transferred to a clean blotting-book of
white bibulous paper, and being placed in the paper-holder may be taken to the
camera and exposed at once. If the paper is not required to be used immediately,
the solutions are mixed in the proportions of the numbers—viz., one of No. 1,
two of No. 2, three of No. 3; and in making the mixture, it is advisable to keep a
measure specially for No. 3, the gallic acid, or else the measure, if used for the
three solutions, will have to be washed out every time, which is very
troublesome, particularly where water is not plentiful.

If the excited paper is required to be kept some hours before use, No. 3 must be
added in still larger proportion, as much as ten or even twenty measures of No. 3
to two of No. 2, and one of No. 1, being used, and even this large dilution is
frequently insufficient to prevent the paper spoiling in hot weather; therefore if
the temperature is high, too much reliance must not be placed on this paper, as it
is peculiarly disappointing, after walking some miles to romantic and beautiful
scenery, to find, when developing the pictures in the evening, that the paper used
was all spoilt before exposure; and it will be seen presently that when the excited
paper is to be carried about for use, it is better to adopt the wax-paper process.
After the excited iodized paper is exposed in the camera—and the time of
exposure cannot be taught, as that speciality is only acquired by experience, and
may vary from five to thirty minutes, or even more—the invisible picture is
developed and rendered visible, not by exposure to the vapour of mercury, as in
Daguerre's process with silver plates, but by a mixture of one of No. 1 with four
of No. 3. The development is carefully watched by looking through the negative
placed before a lighted candle, and the time of development may vary from ten
to thirty minutes, and all the time the picture must be kept wet with the solution,
so that it is better perhaps to make a bath of the solution and lay the picture on
its surface than to pour the liquid over the picture. After the development is
matured, the picture is now washed in clean water, and fixed temporarily, if
required, by immersion in a bath containing 200 grains of bromide of potassium
in one pint of water, or permanently by the hyposulphite of soda, made by
mixing one part of a saturated solution with five or ten of water, or one ounce of
the salt to six or twelve of water; but, as before mentioned, it is better to keep a
Winchester quart full of a saturated solution of hyposulphite of soda, and then it
is always ready for use instead of employing the weights and scales, and
continually weighing out portions of the salt. The picture after fixing is
thoroughly washed with water, and being dried is now placed between the folds
of a wax book—i.e., some leaves of blotting-paper are kept saturated with white
wax, and when a picture is placed between them, and a hot iron passed over the
outside sheet, the wax enters the pores of the paper, and after removing any
excess of wax by passing the picture through a book of bibulous paper, over
which the hot flat iron is passed, the negative picture at last is ready for use, and
any number of positive copies may be taken from it, as already described in the
first experiment, page 139.
This mode of manipulation is called the Talbotype, and before dismissing the
subject another process of iodizing the paper may be explained.

To a solution of nitrate of silver of twenty, thirty, or fifty grains to the ounce of
water, a sufficient number of the crystals of iodide of potassium is added, first to
produce the yellow iodide of silver, and then to dissolve it, so that the yellow
precipitate appears with a small quantity, and disappears with an excess of the
iodide. If this solution is spread over sheets of paper, and these latter then placed
in a bath of water, the iodide of silver is precipitated on the surface, and after
plenty of washing to remove the excess of iodide of potassium, the paper may be
dried, and will keep for any length of time without change. This paper may be
excited, exposed, developed, fixed, and waxed, as already explained.

Fourth Experiment. The Wax-paper Process.

This mode of taking negative photographs begins where the talbotype ends—
viz., by first waxing the paper perfectly and evenly, as already explained,
Cansan's negative paper being preferred. The wax paper is now well soaked in a
bath, made by dissolving one hundred grains of iodide of potassium, six grains
of cyanide of potassium, four grains of fluoride of potassium, ten grains of
bromide of potassium, ten grains of chloride of sodium, in one pint of fresh
whey, with the addition of a little alcohol and a few grains of iodine. When
soaked in this solution for about one hour, the paper is taken out and hung up to
dry.
N.B. With respect to iodizing the wax paper, it is almost better to obtain it ready
prepared, and then every sheet may be relied on. Mr. Melhuish, of Blackheath
and Holborn, supplies it in any quantity, and his paper never fails; the operator
has then only to perform the sensitizing and developing processes. To render the
iodized paper sensitive it is immersed for about six minutes in a bath containing
a solution of nitrate of silver (thirty-five grains to the ounce of water, with forty
drops of glacial acetic acid); the paper is now removed, and washed in two trays
of common clear rain-water or distilled water, and is then dried on between folds
of blotting-paper.
This process may be performed on the previous evening by the light of a candle,
or by day in a room lit by one window covered with four thicknesses of yellow
calico, and after the paper is dry it will keep for three weeks or a month, and
may be exposed in a camera with a three-inch lens of eighteen-inch focus, with
the inch diaphragm, on a bright day from five to fifteen minutes; in bad weather
the exposure must be longer. The picture may be carried home and rendered
visible or developed by immersion in a bath containing a saturated solution of
gallic acid, and as the developing continues, a few drops of the sensitizing

solution of nitrate of silver and glacial acetic acid may be added. Finally, the
picture is fixed by immersion for a quarter of an hour in a solution of
hyposulphite of soda (four ounces of the crystal to one pint of water, or one part
of the saturated solution to eight of water), and being well washed, is then dried,
hung before the fire to melt the wax, and is now ready to print from.

Fifth Experiment. Albumen on Glass Process.

Albumen is the scientific name for the white of egg, of which four ounces by
measure are mixed with one ounce and a half of distilled water, and after being
whisked to a froth, are removed by a spoon into another basin or a beaker glass,
and allowed to stand for several hours and then filtered. Mr. Crookes has
recommended a very ingenious, simple, and useful filter. (Fig. 139.) He says:
"This simple and inexpensive piece of apparatus, which any instrument maker or
glass-blower can supply at a few hours' notice, will be found invaluable in
almost every photographic process on glass. The sponge has this great advantage
over all other kinds of filters, that thick gelatinous liquids—e.g., honey,
albumen, gelatine, meta-gelatine, or the various preservative syrups—flow
through it with the utmost readiness; whilst at the same time dust, air bubbles, or
froth, and dried particles floating in the liquid, are effectually kept back, and if
fitted with stoppers, collodion might be filtered in it; or if the ends were fitted
together with a bit of flexible pipe, the stoppers might be dispensed with
altogether.

Fig. 139.
a b. Glass tube, bent as in picture. c. Piece of damp sponge squeezed into the head of the
tube. Any liquid poured in at b will flow through the sponge until it has attained the same
level in a.

Having poured the albumen on a perfectly clean glass plate, taking care to have
sufficient to run freely over the surface of the glass, the excess is then gently
drained off and the plate turned so as to have the coated side downwards; it is
then fixed in a sling made by taking a stout bit of string about three feet long,
which is doubled and knotted at the fold, leaving the two ends free; two small
triangles or stirrups of silver wire looped at one corner are now tied on to the
ends of the string, and these form a support for the opposite edges of the glass
plate to rest on; the two strings are knotted together at a convenient distance
from the stirrups to prevent the glass slipping out, and the plate is now rotated
rapidly over a heated metallic surface, such as an iron box containing some
burning charcoal or the warming pan, care being taken to avoid dust as much as
possible, and to use only the whites of new-laid eggs. (Fig. 140.) The glass plate,
covered with dry albumen, is now iodized to a straw colour by exposure over a
box containing iodine, as in the Daguerreotype process, and is sensitized by
immersion for three or four minutes in a bath containing a solution of nitrate of
silver (twenty-five grains to an ounce of water); the plate is afterwards washed
in distilled water and left to dry spontaneously, of course in a darkened room.
The plates may then be placed ready for use in a very ingenious tin box devised
by Mr. Crookes, which keeps them perfectly light-tight even in the sun, and at
the same time is less bulky than the ordinary wooden ones. It is made of tin
plate, the cover sliding tight over the top, and more than half way down the
sides; light is further excluded by means of an outer jacket of tin, which is
soldered to the box a little below the centre. The cover thus slides between the
case and the jacket, and renders injury to the plates by the entrance of light an
impossibility. (Fig. 141.)

Fig. 140.
a. Loop for finger. b. The knot which prevents the stirrups of silver wire, c c, slipping off
the corners of the glass plate. d d. The opposite corners of the glass plate on which the
stirrups are placed.

a a. Tin box, with partitions to hold glass plates, b b. The outer jacket, between which and
the box, a, the lid or cover, c, slides.

The sensitive albumenized glass plate is exposed in the camera from fifteen to
thirty minutes, and developed (much in the same way as the paper pictures) with
one ounce of a saturated solution of gallic acid containing ten or fifteen drops of
the sensitizing solution. The plate is usually placed on a levelling stand, and the
solution poured on the glass plate; the development is slow, and may be
quickened sometimes by the application of heat.

The picture is fixed by immersion for a short time in a bath containing one part
of a saturated solution of hyposulphite of soda in eight of water. The pictures
produced by this process are exquisitely defined, provided always the camera is
well focussed, and to assist this operation a magnifying glass may be employed.
After removal from the hyposulphite of soda the plate is well washed with water,
and being allowed to dry spontaneously, is now ready to print from.

Sixth Experiment. The Collodion on Glass Process.

The glass plates for this, as well as the albumen on glass process, should be
cleaned by rubbing them over first with a mixture of Tripoli powder and
ammonia, which is washed off under a tap, and the glass being drained is rubbed
dry and polished with a clean calico duster kept exclusively for this purpose.
The iodized collodion is now poured on, and the excess returned to the bottle.
Collodion can be made very easily, but if prepared without due precautions, it
cannot be used afterwards, and reminds one of the old story of the enthusiastic
son, who, when asking his father's permission to espouse the beloved,
enumerated amongst her other accomplishments, the fact that she could make a
pudding, and was answered by the bluff question, "But can you eat it
afterwards?" So it is with collodion: a great deal of messing and loss of time is
saved by purchasing it of the various makers, amongst whom may be specially
noticed Mr. Richard Thomas, of 10, Pall Mall, who has devoted the whole of his
attention to the preparation of this important photographic chemical, and with a
success which his numerous patrons can well testify. The collodion is sold either
mixed with the iodizing solution, or the two can be obtained separately, with
directions on the bottles as to the quantities to be mixed together.
The plate covered with the iodized collodion is quickly transferred to a bath
containing a solution prepared in the following manner:—Dissolve four ounces
of nitrate of silver in eight ounces of water, and to this add twenty grains of
iodide of potassium in one ounce of water; shake them together, and then pour
the whole into fifty-six ounces of distilled water, and in half an hour add one
ounce of alcohol and half an ounce of ether; agitate the whole and filter the next
morning. The collodion plate is kept in this solution for a certain period, only
learnt by experience, and should be occasionally lifted out to see if a uniform
transparency is obtained; say that the immersion may be continued for five
minutes, it is now ready for the camera, and may be exposed from about one to
two minutes, or more if the light is deficient; the time of exposure is also a
matter of practice, mere directions can be of no use in this stage of the process.

The picture is developed on a levelled stand, with a solution of three grains of
pyrogallic acid in three ounces of water, to which sixty drops of glacial acetic
acid have been added. When fully developed the plate is washed with water and
fixed with a solution of hyposulphite of soda, consisting of one part of the
saturated solution to eight of water, again thoroughly but gently washed, so as
not to endanger the separation of the film from the glass; it is allowed to dry
spontaneously, and being coated with amber varnish (a solution of amber in
chloroform) is now ready to print from. It is, perhaps, hardly necessary to add,
that the sensitizing and developing processes must be performed in a dark room.

Fig. 142.
a. Glass or gutta-percha bath to hold the sensitizing solution. b. Glass, with piece cemented
on the end to hold the prepared glass plate, c, whilst dipped in the bath, a. The plate c has a
cross in one corner to show prepared side.

Fig. 143.
First effect of peripatetic photography on the rural population.

BROMINE.

Bromine (βρωμος, a bad odour). Symbol, Br. Combining proportion, 80.
Specific gravity, 2.966.
In a previous portion of this work, the connexion between chlorine, iodine, and
bromine has been pointed out; and as we have to notice the colour of the element
bromine, the chromatic union of the triad may be alluded to. These elements
present very nearly all the colours of the spectrum:

Bromine red to orange.
Chlorine yellow to green.
Iodine blue, indigo, violet.

These three elements also furnish examples of the three conditions of matter;
iodine being a solid, bromine a fluid, chlorine a gas; the relation of their
combining proportions is also curious: as might be expected, the fluid bromine
takes an intermediate position, and (according to the axiom that half the sum of
the extremes is equal to the mean) by dividing the combining proportions of

iodine and chlorine, and adding them together, we have, as nearly as possible,
the combining proportion of bromine:

Chlorine 35÷ 2= 17.75
Iodine 126÷ 2= 63
————
80.75

The combining proportion of bromine is 80, but 80.75 is so near, that it may
reasonably be conjectured future experiments will reduce the number of the
three elements, and may prove that they are only modifications of a single one.
This is the only kind of alchemy which is tolerated in the nineteenth century, and
any philosopher who will reduce the number of elements, and prove that some
of them are only modifications of others, will achieve a renown that must
transcend the éclat of all previous discoverers.
Bromine was discovered by Balard, in 1826, and, like chlorine and iodine, is a
constituent of sea water. The chief source of bromine is a mineral spring at
Kreutznach, in Germany. The process by which it is obtained offers a good
example of chemical affinity; the water of the mineral spring is evaporated, all
crystallizable salts removed, and a current of chlorine gas passed through the
remaining solution, which changes to a yellow colour, in consequence of the
liberation of the bromine by the combinations of chlorine with the bases
previously united with the former; the liquid is then shaken with ether, which
dissolves out the bromine. In the next place, the etherial solution is agitated with
strong solution of potassa, and is thus obliged to part with the bromine which is
converted into bromate of potassa; this is ultimately changed by fusion to
bromide of potassium; and by distillation with black oxide of manganese and
sulphuric acid, the bromine is finally obtained. Six processes are therefore
necessary before the small quantity of bromine contained in the mineral spring-
water, is separated.

First Experiment.

Bromine is a very heavy fluid, which should be preserved by keeping it in a
bottle covered with water; when required, a few drops may be removed by
means of a small tube, and dropped into a warm bottle, which is quickly filled
with the orange-red vapour. If some phosphorus is placed in a deflagrating
spoon, and exposed to the action of bromine vapour, it takes fire spontaneously.

Second Experiment.

Powdered antimony sprinkled into the vapour of bromine immediately takes fire.

Third Experiment.

A burning taper immersed in a bottle containing the vapour of bromine is
gradually extinguished.

Fourth Experiment.

Liquid bromine exposed to a freezing mixture of ice and salt, or reduced to a
temperature of about eight degrees below zero, solidifies into a yellowish-
brown, brittle, crystalline mass.

Fifth Experiment.

A solution of indigo shaken with a small quantity of the vapour of bromine is
quickly bleached. Many substances, when brought in contact with liquid
bromine, combine with explosive violence, and therefore experiments with
liquid bromine are not recommended, as all the most instructive and conclusive
results can be obtained by the use of the vapour of bromine, which is easily
procured by allowing a few drops to fall into a warm, dry bottle.
Bromine, as already mentioned, is used in the art of photography.

FLUORINE.

Symbol, F. Combining proportion, 19.
This singular element seems almost to embody the ancient idea of the
alchemists, being a sort of alkahest, or universal solvent; or in plainer language,
its affinities for other bodies are so powerful, that it attacks every substance (not
even excepting gold), at the moment of its liberation, and combines therewith, so
that its isolation has not yet been effected. Chemists who assert that they have
been able to obtain fluorine in the elementary condition, pronounce it to be a gas
which possesses the colour of chlorine; but the experiments, as hitherto
conducted, render that statement extremely doubtful.

The only interesting fact connected with fluorine, is the remarkable property of
attacking glass and other silicious bodies, belonging to its combination with
hydrogen gas, called hydrofluoric acid. This acid is easily obtained and used by
placing some powdered fluorspar in a leaden tray six inches square and two
inches deep. If sulphuric acid is now mixed with the powdered spar, so as to
form a thin paste, and heat applied, the vapour of the hydrofluoric acid quickly
rises, and can be employed to etch a glass plate upon which a drawing may have
been previously traced by scratching away the wax, with which it is first coated.
By heating the glass plate before a fire, a sufficient quantity of wax is soon
melted on to it by merely rubbing the wax against the glass plate; any excess
should be avoided, if a well-executed drawing is required to be etched on its
surface. (Fig. 144.)

Fig. 144.
a a a. The glass plate, with the waxed side downwards, placed on the leaden tray containing
the fluorspar and sulphuric acid. b. Spirit lamp.

The wax plate must not remain too long over the leaden tray, as the heat is apt to
melt the wax, when the acid not only attacks those parts from which the wax has
been removed by the etching needle, but also the surface of the glass generally, and
thus the clearness of the design is spoilt. After exposure—and it is as well to
prepare two or three glass plates for the experiment—the wax is quickly removed
by rubbing and washing with oil of turpentine, and the design (beautifully etched
into the glass) is then apparent.

CHAPTER XII.
CARBON, BORON, SILICON, SELENIUM, SULPHUR,
PHOSPHORUS.

This group of non-metallic elements has been frequently styled "Metalloids,"
meaning substances allied to, but not possessing, all the properties belonging to a
metallic substance; and therefore perhaps the expression, non-metallic solids, is the
best that can be adopted. They may be subdivided into two classes of three each,
which have properties more or less allied to each other—viz.,
Carbon, Boron, Silicon; and
Selenium, Sulphur, Phosphorus.

CARBON.

Symbol, C; Combining Proportion, 6.
This element has almost the property of ubiquity, and is to be found not only in all
animal and vegetable substances, in common air, sea, and fresh water, but also in
various stones and minerals, and especially in chalk and limestone.
There is, perhaps, no element which offers a greater variety of amusing
experiments and elementary facts than carbon, whether it be considered either in
its simple or combined state.
A piece of carbon, in the shape of the Koh-i-Noor, was one of the chief attractions
at the first Exhibition in Hyde Park. The diamond is the hardest and most beautiful
form of charcoal; how it was made in the great laboratory of nature, or how its
particles came together, seems to be a mystery which up to the present time has not
yet been solved, at all events no artificial process has yet produced the diamond.
Sir D. Brewster, speaking of the Koh-i-Noor, remarks that on placing it under a
microscope, he observed several minute cavities surrounded with sectors of
polarized light, which could only have been produced by the expansive action of a
compressed gas or fluid, that had existed in the cavities when the diamond was in
the soft state.

Now it is known that bamboo, which is of a highly silicious nature, has the
property of depositing in its joints a peculiar form of silica, called tabasheer.
Silicon is one of the triad with carbon—i.e., it is allied to carbon on account of
certain analogies; may it not then be supposed that, in times gone by, ages past,
when the atmosphere was known to be highly charged with carbonic acid gas,
there might possibly have existed some peculiar tree which had not only the power
of decomposing carbonic acid (possessed by all plants at the present period), but
was enabled, like the bamboo, to deposit, not silica, which is the oxide of silicium,
but carbon, the purest form of charcoal—viz., the diamond? Speculation in these
matters is ever more rife than stern proof, and it may be stated, that all attempts to
manufacture this precious gem (like those of the alchemists with gold and silver)
have most signally failed.

First Experiment.

Box and various woods, dried bones, and different organic matters, placed in a
nearly close iron or other vessel, and heated red hot, so that all volatile matter may
escape, leave behind a solid black substance called charcoal. If that kind obtained
from bones, and termed bone black or ivory black, is roughly powdered, and
placed in a flask with some solution of indigo or some vinegar, or syrup obtained
by dissolving common moist sugar in water, and boiled for a short period, the
colour is removed, and on filtering the liquid it is found to be as clear and
colourless as water, provided sufficient ivory black has been employed.

Second Experiment.

Charcoal is a disinfectant, and is used for respirators; it has even been
recommended medically, and charcoal lozenges can be bought at various chemists'
shops. If a few drops of a strong solution of hydrosulphuret of ammonia (which
has the agreeable odour belonging to putrid eggs) is mixed with half a pint of
water, it will of course smell strongly, and likewise precipitate Goulard water, or a
solution of acetate of lead black; but on shaking the water with a few ounces of
charcoal, it no longer smells of sulphuretted hydrogen, and if filtered and poured
into a solution of lead does not turn it black. This chemical action of charcoal,
independent of its seeming mechanical attraction for colouring matter, would
appear to show that the pores of charcoal contain oxygen, which in that peculiar
condensed state destroys colouring matter, and oxidizes other bodies.

Third Experiment.

A very satisfactory experiment, proving that the diamond and plumbago or black
lead are identical with charcoal, although differing in outward form and purity, can
be made at a little cost, by purchasing a fragment of refuse diamond, called
"boart," of Mr. Tennant of the Strand. A small piece costs about five shillings. The
fragment should be carefully supported by winding some thin platinum wire round
it, as, if the wire is too thick, it cools down the heat of the bit of diamond and
prevents it kindling in the oxygen gas. A difficulty may arise in preparing the
fragment, in consequence of the wire continually slipping off. The "boart" should
therefore be grasped by the thumb and first finger, and the wire wound round; then
it must be carefully turned and again wound across with the platinum wire, as in
the sketch below. (Fig. 145.)

Fig.
145.
a. The platinum wire. b. The fragment of "boart" or refuse diamond.

A piece of black lead (so called) may now be taken from a lead pencil and also
supported by platinum wire; likewise a bit of common bark charcoal or hard coke.
Three bottles of oxygen should now be prepared from chlorate of potash and oxide
of manganese, an extra bottle being provided for the diamond in case there should
be any failure in its ignition. The bark charcoal can be first ignited by holding a
corner in the spirit lamp for a few seconds; when plunged into oxygen it
immediately kindles and burns with rapidity, and if the cork is well fitted, the

product of combustion—viz., carbonic acid gas—is retained for future
examination. The small piece of black lead is next heated red hot in the flame of
the spirit lamp, and being attached by its platinum support to a stiff copper wire
thrust through a cork, which fits the bottle of oxygen, is placed whilst red hot in
the gas, and continues to glow until consumed. The fragment of diamond is by no
means, however, so easily ignited, the flame of the spirit lamp must be urged upon
it with the blowpipe; when quite red hot, an assistant may remove the stopper from
the bottle of oxygen, and the person heating the diamond should plunge it instantly
into the gas; if this is dexterously managed, the fragment of boart glows like a
little star, and the combustion frequently continues till the piece diminishes so
much that it falls out of its platinum support.
Sometimes the diamond cools down without igniting, the same process must
therefore be repeated, and a few extra bottles of oxygen will prevent
disappointment, as every failure destroys the purity of the gas by admixture with
atmospheric air when the stopper is removed. (Fig. 146.)

Fig. 146.
a. Bottle containing bark charcoal. b. Ditto the plumbago or black lead. c. Ditto the diamond.

The combustion having ceased in the three bottles, the corks are removed, and the
glass stoppers again fitted for the purpose of testing the products, which offer no
apparent indication of any change, as oxygen and carbonic acid gas are both
invisible. In each bottle a new combination has been produced; the charcoal, the
black lead, the diamond have united with the oxygen, in the proportion of six parts
of carbon to sixteen parts of oxygen, to form twenty-two parts of carbonic acid
gas, which may be easily detected by pouring into each bottle a small quantity of a
solution of slacked lime in water, called lime water. This test is easily made by
shaking up common slacked lime with rain or distilled water for about an hour, and
then passing it through a calico or paper filter. The test, though perfectly clear

when poured in, becomes immediately clouded with a white precipitate, usually
termed a milkiness, no doubt in allusion to the London milk, which is supposed to
contain a notable proportion of chalk and water, for in this case the precipitate is
chalk, the carbonic acid from the diamond and the charcoal having united with the
lime held in solution by the water and formed carbonate of lime, or chalk, a
substance similar in composition to marble, limestone, Iceland or double refracting
spar, these three being nearly similar in composition, and differing only, like
carbon and the diamond, in external appearance.
The milkiness, however, must not be held as conclusive of the presence of
carbonic acid gas until a little vinegar or other acid, such as hydrochloric or nitric,
has been finally added; if it now disappears with effervescence (like the admixture
of tartaric acid, water, and carbonate of soda), the little bubbles of carbonic acid
gas again escaping slowly upwards, leaving the liquid in the three bottles quite
clear, then the experimentalist may sum up his labours with these effects, which
prove in the most decisive manner that common charcoal, black lead, and the
diamond, are formed of one and the same element—viz., carbon.

Fourth Experiment.

Having effected the synthesis (or combining together) of the diamond and oxygen,
it is no longer possible to recover it in its brilliant and beautiful form. If the
product of combustion is retained in a flask made of thin, hard glass, and two or
three pellets of the metal potassium are placed in directly after the diamond has
ceased to burn, and the flame of a spirit lamp applied till the potassium ignites,
then the metal, by its great affinity for oxygen, takes away and separates it again
from that which was formerly the diamond; but instead of the jewel being
deposited, there is nothing but black, shapeless, and minute particles of carbon
obtained, if the potash produced is dissolved in water, and the charcoal separated
by a filter.

Fifth Experiment.

Chalk is made by uniting carbonic acid gas with lime; it may therefore be
employed as a source of the gas, by placing a few lumps of chalk, or marble, or
limestone, in a bottle such as was used in the generation of hydrogen gas; on the
addition of some water and hydrochloric acid, effervescence takes place from the
escape of carbonic acid gas, and the cork and pewter pipe being adapted, it may be
conveyed by its own gravity into glasses, jugs, or any other vessels, and a

pneumatic trough will not be required. Carbonic acid gas has a specific gravity of
1.529, and is therefore rather more than half as heavy again as atmospheric air.

Sixth Experiment.

In order to satisfy the mind of the operator that the gas obtained from chalk is
similar to the product of combustion from the diamond, some lime-water may be
placed in a glass, and the gas from the bottle allowed to bubble through it; instantly
the same milkiness is apparent, which again vanishes on the addition of acid. And
this experiment is rendered still more striking if a lighted taper be placed in the
glass just after the addition of the acid, when it will be immediately extinguished.

Seventh Experiment.

If a lady's muff-box, supported by threads or chains, is hung on one end of a scale-
beam, and counterbalanced by a scale pan and a few shot, it is immediately
depressed on pouring into the muff-box a quantity of carbonic acid gas, which may
have been previously collected in a large tin vessel. After showing the weight of
the gas, the box is detached from the scale-beam, and the contents poured upon a
series of lighted candles, which are all extinguished in succession. (Fig. 147.)

Fig. 147.
a. Carbonic acid gas poured out of the tin box into b, the muff-box. b b. Detached muff-box,
and candles extinguished by the carbonic acid gas poured from it.

Eighth Experiment.

The property of carbonic acid gas of extinguishing flame, as compared with the
contrary property of oxygen, is nicely shown by first passing into a large and tall
gas jar one half of its volume of oxygen gas; a large cork perforated with holes
may be introduced, so as to float upon the surface of the water in the gas jar, and is
usefully employed to break the violence with which the carbonic acid enters the
gas jar, as it is passed in to fill up the remaining half volume of the gas jar, which
now contains oxygen at the top, and carbonic acid gas at the bottom. On testing the
contents of the jar with a lighted taper, it burns fiercely in the oxygen, but is
immediately extinguished in the carbonic acid gas, being alternately lighted and
put out as it is raised or depressed in the gas jar.

Ninth Experiment.

A little treacle, water, and a minute portion of size, may be placed with some yeast
in a quart bottle, to which a cork and pewter or glass pipe is attached; directly the
fermentation begins, quantities of carbonic acid gas may be collected, and tested
either with lime-water or the lighted taper.

Tenth Experiment.

Some clear lime-water placed in a convenient glass is quickly rendered milky on
passing through it the air from the lungs by means of a glass tube; thus proving
that respiration and (as shown by the ninth experiment) fermentation, as well as the
combustion of charcoal, produce carbonic acid gas.

Eleventh Experiment.

Carbonic acid gas is not only generated by the above processes, but is liberated
naturally in enormous quantities from volcanoes, and from certain soils: hence the
peculiar nature of the air in the Grotto del Cane. Dogs thrust into this cave drop
down immediately, and are immediately revived by the tender mercies of the
guides, who throw them into the adjoining lake. This natural phenomenon is well
imitated by taking a box, open at the top, and nailing on to it a frame of cardboard,
which may be painted to represent rocks, taking care that a portion (about three
inches deep) at the lower part is well pasted to the box at the edges, so that the gas
may be retained; a hole is perforated at the top side to admit a lighted taper, and
another at the side for the pipe from the carbonic acid bottle; when the bottom is

filled with gas, a taper is applied, which is found to burn in the upper part, but is
immediately extinguished when it reaches the lower division, where the three
inches of pasteboard prevent it falling out: thus showing in a simple manner why a
guide may enter the cave with impunity, whilst the dog is rendered insensible
because immersed in the gas. (Fig. 148.)

Fig. 148.
a a. The box model of the Grotto del Cane. b b. Cardboard fixed in front of box, and painted
to imitate rocks. c. Carbonic acid gas bottle, with bent tube passing through hole in the side of
the box. A taper introduced at d burns in the upper, and is extinguished in the lower, part of
the model.

Twelfth Experiment.

Many fatal accidents have occurred in consequence of the air in deep pits, graves,
&c., becoming unfit for respiration by the accumulation of carbonic acid gas,
which may arise either from cavities in the soil, where animal matter has
undergone decomposition, or it may happen from the depth and narrowness of the
hole or well preventing a proper draught or current of air, so that it becomes foul
by the breathing of the man who is digging the pit. Air which contains one or two
per cent. of carbonic acid will support the respiration of man, or maintain the flame
of a candle; but it produces the most serious results if inhaled for any length of
time; a lighted candle let down into a well (suspected to contain foul air) before the
descent of the person who is to work in it, may burn, but does not indicate the
presence of the small percentage of the poison, carbonic acid. Frequently no
trouble is taken to test the air with a lighted candle; a man is lowered by his
companions, who see him suddenly become insensible, another is then lowered
quickly to rescue him, and he shares the same fate; and indeed cases have occurred
where even a third and a fourth have blindly and ignorantly rushed to their death in
the humane attempt to rescue their fellow creatures. What is to be done in these
cases? Are the living to remain idle whilst the unfortunate man is suffocating

rapidly at the bottom of the pit? No; provided they do not venture themselves into
the pit, they may try every known expedient to alter the condition of the foul air, so
as to enable them to descend to the rescue. One should be despatched to any
neighbouring house or cottage for a pan of burning coals; if any slacked lime is to
be had, it may be rapidly mixed with water, and poured down the side of the pit; a
bundle of shavings set on fire and let down, keeping it to one side, so as to
establish a current; or even the empty buckets constantly let down empty and
pulled up full of the noxious air, may appear a somewhat absurd step to take, but
under the circumstances any plan that will change the air sufficiently to enable
another person to descend must be adopted; in proof of which the following
experiments may be adduced:
Fill a deep glass jar with carbonic acid, and ascertain its presence with a lighted
taper; if a beaker glass to which a string is attached is let down into the vessel and
drawn up, and then inverted over a lighted taper, the utility of this simple plan is at
once rendered apparent; the beaker glass represents the empty bucket, and can be
let down and pulled up full of carbonic acid until a sensible change in the
condition of the atmosphere is produced. The best plan, however, is to set the air in
motion by heat obtained from burning matter, or even a kettle of boiling water,
lowered by a cord, and this fact is well shown by putting a small flask full of
boiling water, and corked, at the bottom of the deep glass jar containing the
carbonic acid gas, which rises like other gases when sufficiently heated, and
passing away, mixes with the surrounding air. (Fig. 149.)

Fig. 149.
a. Deep jar containing carbonic acid gas, which is being removed by the little glass bucket. b.
Jar containing corked flask of boiling water on a pad; the heated gas rises and the cold air
descends to take its place.

Thirteenth Experiment.

Carbonic acid gas dissolved in water under considerable pressure, forms that most
agreeable drink called soda-water; the gas is not only useful in this respect, but has
been applied most successfully by Mr. Gurney to extinguish a fire on a gigantic
scale, which had been burning for years in the waste of a coal mine in Scotland.
The same gas, generated suddenly by the combustion of a mixture of nitre, coke
dust, and clay, or plaster of Paris, in vessels of a peculiar construction, has formed
the subject of a patent by Phillips, since merged into the Fire Annihilator
Company. The instrument is peculiarly adapted for shipping, and might, if properly
used, be the means of saving many ships and valuable lives. (Fig. 150.)
Its practical value is established by the test of actual use: in the streets, by the
Leeds Fire Brigade, and by firemen of the Fire Annihilator Company, temporarily
stationed at Liverpool and Manchester.
The Fire Annihilator has been formally recognised by the Government Emigration
Commissioners, who introduced into the Passengers' Act, 1852, in §24, the
alternative, "Or other apparatus for extinguishing fire," with distinct reference to
this invention, and subsequently by formal order authorized their officers to pass
ships carrying Fire Annihilators.

Fig. 150.
a. A carriage with six fire annihilators, No. 5 size, fitted with moveable pipes. The body of the
carriage forms a tank for forty gallons of water; the tank is filled at a bunghole in the
platform; a patent tap is fitted to the rear of the carriage; a spigot is placed near the end
upright of the rail; a hand-pump is placed in the box at rear of carriage; a leather bucket with
foot-holds and three canvas buckets are hung on the carriage; a hammer for removing and
driving on the cover of the fire annihilator, and a nut wrench for the No. 10 truck, are placed
in the box. b. A fire annihilator, No. 10 size, with moveable pipe, on a spring truck, is attached
to the carriage.

The battery is fitted with shafts for one horse. A pole is also provided to fix across the shafts,
so that the battery may be drawn by hand.

Monsieur Adolphe Girard has proposed that all houses should be provided with an
apparatus for the generation of carbonic acid gas, placed outside the building,
which is to be conveyed along the ceiling by means of pipes perforated with
numerous holes, and to be put in operation directly a fire breaks out. This plan,
however ingenious, could hardly supply the carbonic acid gas with sufficient
rapidity, and it is to be feared would utterly fail in practice. (Fig. 151.)

Fig. 151.
a. Tank containing acid, communicating by a pipe with b, half filled with chalk and water. c c
C C. Pipes conveying carbonic acid from the generator b, to the ceiling, where it is discharged
from numerous holes on the fire beneath.

BORON.

Symbol, B; combining proportion, 10.9.
Discovered by Homberg, in 1702, in borax, which is a biborate of soda
(NaO,2BO3), and is used very extensively in the manufacture of glass; also for
glazing stoneware and soldering metals; it is also a valuable flux in various
crucible operations, whilst in testing minerals with the blowpipe it is invaluable.
Borax is made either from tincal, a substance that occurs naturally in some parts of
India, China, and Persia, or by the addition of carbonate of soda to boracic acid, a

substance obtained from the volcanic districts of Tuscany, whence it is imported to
this country, and used in the manufacture of borax.
The element boron may be obtained by placing some pure boracic acid and some
small bits of potassium in a tube together, and applying the flame of a spirit-lamp,
a glow of heat takes place, and when the tube is cold the potash may be washed
away, and the boron remains as a dark brownish powder somewhat resembling
carbon. M. St. Claire Deville and Wöhler have lately made some important
discoveries with respect to this element, and disproved the statement that it is
uncrystallizable. Their researches prove it to be producible under three forms and
of various colours, such as honey-yellow and garnet-red, the crystals in some cases
being like diamonds of the purest water—i.e., limpid and transparent. A new
combination of aluminium and boron is stated to possess the most remarkable
properties. It is harder than the diamond, and in the state of powder will cut and
drill rubies, and even the diamond itself, with more facility than diamond powder.
Deville and Wöhler incline to the belief that the diamond is dimorphous, and
capable (in conditions yet to be described) of assuming the same forms as boron.
At a high temperature, boron, like titanium, absorbs nitrogen only from the
atmosphere, and rejects the oxygen. (Query, may not some of those remarkably
hard black diamonds prove to be boron?)

SILICON.

Symbol, Si; combining proportion, 21.3.
The great Berzelius was the first to obtain this element in 1823. Silicon in the pure
state is a dark brown powder; if ignited at a very high temperature it assumes a
chocolate colour, which is supposed to be the allotropic condition, because it no
longer burns when heated moderately in oxygen or air, and is not attacked by
hydrofluoric acid. The most interesting combination of silicon is the teroxide
called silicic acid, silica (SiO3). Silicon is next to oxygen so far as regards its
plentifulness, and is found in the state of silica in nearly every mineral, but
especially in rock crystal, quartz, flint, sand, jasper, agate, and tripoli. It is largely
used in the manufacture of glass, and a most useful "soluble glass" is obtained by
melting together in a crucible fifteen parts of sand, ten parts of carbonate of potash,
and one part of charcoal.
Cold water merely washes away the excess of alkali, and after this is done the
powdered soluble glass may be boiled with water in the proportion of one of the
former with five of the latter, when it gradually dissolves; the solution may be
evaporated to a thick pasty fluid, which looks like jelly when cool, and on

exposure to the air in thin films changes to a transparent, colourless, brittle, but not
hard glass. Wood, cotton, and linen fabrics are rendered less combustible when
coated with this glass, which excludes the oxygen of the air, and it has lately been
employed to fill up the porous and capillary openings in stone exposed to the
atmosphere, and is stated to be very efficacious as a preservative of the stone in
some cases.

SULPHUR.

Symbol, S; combining proportion, 16.
Sulphur, like charcoal, is of common occurrence in nature, and is chiefly supplied
from the volcanic districts of Tuscany and Sicily: there is an abundance of this
element in the United Kingdom, but then it is locked up in combination with iron,
copper, and lead, under the name of iron pyrites, copper pyrites, galena; and whilst
Sicily and Tuscany supply thousands of tons weight in the uncombined state, it is
not, of course, worth while to go through expensive operations at home for the
separation of sulphur from the ores. During the dispute between Sicily and
England, several patents were secured for new and economical processes by which
sulphur was obtained from various minerals; and had this country been excluded
from a supply of native sulphur, no doubt some of these patents would now be in
active operation.
It is almost possible to estimate the commercial prosperity of a country by the
sulphur it consumes, not, happily, by their warlike operations, but in the
manufacture of oil of vitriol or sulphuric acid, which is the starting point of a great
number of useful arts and manufactures.

First Experiment.

Some very curious results may be obtained by heating sulphur at certain
temperatures; in the ordinary state it is a pale yellow solid, and when subjected to a
temperature of 226° Fahr. it melts to a brownish-yellow, transparent, thin fluid;
according to all preconceived notions of the properties of substances which liquify
by an increase of heat, it might be imagined that every additional degree of heat
would only render the melted sulphur still more liquid, but strange to say, when it
reaches a temperature of about 320° Fahr. it changes red, and thick like treacle; and
as the heat rises it becomes so tenacious, that the ladle in which it is contained may
be inverted, and the sulphur will hardly flow out: at about 482° Fahr. it again
becomes liquid, but not so fluid as at the lower temperature. If allowed to cool
from 482° Fahr., the above results are simply inverted; the sulphur becomes thick,

again liquid, and finally crystallizes in long, thin, rhombic prisms, which are seen
most perfectly by first allowing a crust of sulphur to form on the liquid portion,
and then having made two holes in this crust, the sulphur is poured out, when the
remainder is found in the interior of the crucible crystallized in the form already
mentioned. Sulphur takes fire in the air when exposed to a heat of about 560°
Fahr., and burns with a pale blue flame; and, as already stated, it may be poured
from a considerable height on a still dark night, and produces a continuous column
of blue fire, just like an unbroken current of electricity. If the melted and burning
sulphur is received into a vessel containing boiling water, it is no longer yellow,
but assumes a curious allotropic state, in which it is a reddish-brown, transparent,
shapeless mass, that may be easily kneaded and used for the purpose of taking
casts of seals, which become yellow in a few days, and are found then to be hard
and crystallized.

Second Experiment.

Sulphur vapour, in one sense, may be regarded as a supporter of combustion: if a
clean Florence oil-flask is filled with copper turnings, and a little roughly-
powdered sulphur sprinkled in, and heat applied, the copper glows with an intense
heat, and burning in the vapour of the sulphur, produces a sulphuret of copper;
from this compound the sulphur may be again obtained by boiling the powdered
sulphuret with weak nitric acid, which oxidizes and dissolves the copper, leaving
the greater part of the sulphur behind, which may be collected, melted, and burnt,
and will be found to display all the properties belonging to that element. This
experiment is a very good example of simple analysis; and if the copper is weighed
and likewise the combined sulphur, a good notion may be formed of the principles
of combining proportions.

Third Experiment.

A little sulphur burnt under a gas jar, or in any convenient box (a hat-box, for
instance), produces sulphurous acid (SO2), which will bleach a wetted red rose or
dahlia, and many other flowers. This gas is employed most extensively in
bleaching straw, and sundry woollen goods, such as blankets and flannel, and
likewise silk, and is perhaps one of the best disinfectants that can be employed;
when fever has been raging in the dwellings of the poor, as in cottages, &c., all
metallic substances should be removed, the doors and windows closed, the
bedding, &c., well exposed, and then a quantity of sulphur should be burnt in an
old frying-pan placed on a brick, taking care to avoid the chance of setting the

place on fire; after a few hours the doors and windows may be opened, and the
disinfectant will be found to have done its work cheaply and surely.

Fourth Experiment.

The presence of sulphur in various organic substances, such as hair, the white of
egg, and fibrine, is easily detected by heating them in a solution of potash, and
adding acetate of lead as long as the precipitate formed is redissolved; finally the
solution must be heated to the boiling point, when it instantly becomes black by
the separation of sulphuret of lead.

Fifth Experiment.

Sulphuric acid, HO,SO3, or oil of vitriol, is made in such enormous quantities that
it is never worth while to attempt its preparation on a small scale. In consequence
of its great affinity for water, many energetic changes are produced by its action.
Oil of vitriol poured on some loaf sugar placed in a breakfast-cup with the addition
of a dessert-spoonful of boiling water, rapidly boils and deposits an enormous
quantity of black charcoal. If a word be written on a piece of white calico with
dilute sulphuric acid, and then rapidly and thoroughly washed out, no visible
change occurs; but if the calico is exposed to heat, so that the excess of water is
driven off, the remaining and now concentrated oil of vitriol attacks the calico, and
the word is indelibly printed in black by the decomposition of the fabric of cotton.
A very remarkable process has lately been introduced by Mr. Warren de la Rue, by
which paper is converted into a sort of tough parchment-like material, called
ametastine, by the action of oil of vitriol and water of a certain fixed strength; and
any departure from the exact proportions destroys the toughness of the paper. After
the paper has been acted upon by the acid, it becomes extremely tenacious, and
will support a considerable weight without breaking. Mr. Smee has used this
ametastine in the construction of an hygrometer, and states that it may save many a
traveller from catching a severe rheumatism in a damp bed.

Sixth Experiment.

When the vapour of sulphur is passed over red-hot charcoal and the product
carefully condensed, a peculiar liquid is obtained, called bisulphide of carbon
(CS2), which possesses a peculiar odour, is extremely transparent and brilliant-
looking, and enjoys a high refractive power. This liquid is used as a solvent for
phosphorus and other substances, and is extremely volatile and combustible, and

burns silently with a pale blue flame. The combustion of its vapour, mixed with
certain gases, offers a good example of the fact that slow burning may be a
peaceful experiment, whilst very rapid combustion often resolves itself into an
explosion. Thus, if a few drops of bisulphide of carbon are dropped into a narrow-
mouthed dry quart bottle containing common air, and flame applied, the
combustion takes place with rapidity, a rushing or roaring sound being audible, in
consequence of the diffused vapour being supplied with more oxygen, and burning
more rapidly than it would do if simply consumed from a stick or glass rod wetted
with the fluid. A still greater rapidity of combustion is ensured by dropping some
bisulphide of carbon into a long stout cylindrical jar, fifteen inches long and three
inches in diameter, containing nitric oxide gas (NO2); when flame is applied the
mixture burns with a bright flash and some noise, and if burnt in a narrow mouthed
bottle would most likely blow it to atoms.
The greatest rapidity of combustion, and of course the loudest noise, is obtained by
shaking some bisulphide of carbon in a similar stout and strong cylindrical jar
filled with oxygen gas, but in this case the jar must be protected with a double
cylinder of stout wire gauze; it does not always break, but if it is blown to
fragments each particle becomes a lancet-shaped piece of glass, which is capable
of producing the most dangerous wounds. (Fig. 152.)

Fig. 152.
a. Air and bisulphide of carbon. b. Nitric oxide and ditto. c. Oxygen and ditto. d d. Stout
cylinder of double wire gauze, open top and bottom.

SELENIUM.

Selenium (σεληνη, the Moon[B]); symbol, Se; combining proportion, 39.5.

This new metallic element is allied to sulphur, and is a species of chemical
curiosity, being found in minute quantities in various minerals; it may be melted
and cast into any form. Medallions of the discoverer (Berzelius) of selenium, in
little cases, are imported from Germany, for the cabinets of the curious.
[B] Called selenium on account of its strong analogy to the metal tellurium (tellus, the
earth).

PHOSPHORUS.

Phosphorus (φως, light; φερειν, to bear; symbol, P; combining proportion, 32.)
Monsieur Salverte, in his work on the Occult Sciences of the Ancients, quotes a
remarkable story respecting the probable discovery of the nature of phosphorus in
1761:—"A Prince San Severo, at Naples, cultivated chemistry with some success;
he had, for example, the secret of penetrating marble with colour, so that each slab
sawed from the block presented a repetition of the figure imprinted on its external
surface. In 1761, he exposed some human skulls to the action of different reagents,
and then to the heat of a glass furnace, but paying so little attention to his manner
of proceeding, that he acknowledged he did not expect to arrive a second time at
the same result. From the product he obtained a vapour, or rather a gas was
evolved, which kindling at the approach of a light, burned for several months
without the matter appearing to die or diminish in weight. San Severo thought he
had found, the impossible secret of the inextinguishable lamp, but he would not
divulge his process, for fear that the vault in which were interred the princes of his
family should lose the unique privilege with which he expected to enrich it, of
being illuminated with a perpetual lamp." Had he acted like a philosopher of the
present day, San Severo would have attached his name to the important discovery
of the existence of phosphorus in the bones, and made public the process by which
it might be obtained.
This element, formerly sold at four or five shillings the ounce, has now fallen so
much in price, from the greater demand and larger production, that it may be
bought for a few shillings the pound, and is imported in tin cases in large quantities
from Germany. It was discovered about two hundred years ago by Brandt, a
merchant of Hamburg, and may be prepared on a small scale by distilling at a red
heat phosphoric acid previously fused with one-fourth of its weight of powdered
charcoal.

First Experiment.

Phosphorus, when pure, is without taste or colour, but generally of a very pale
buff-colour, and semi-transparent; it is extremely combustible, and is usually
preserved under the surface of water; when perfectly dry, a thin slice will take fire
at 60° Fah., and burns with great brilliancy. Considering the heat produced during
the combustion of phosphorus, it might be thought that it would infallibly set fire
to any ordinary combustible, such as paper or wood, but this is not the case when
phosphorus is employed by itself, as may be proved by the following experiment.
Cut five very small pieces of phosphorus, and place them like the five of diamonds
on a sheet of cartridge-paper laid upon the table, set the bits of phosphorus on fire,
when they will be rapidly burnt away leaving only five black spots, but not firing
the paper, as would be the case if some red-hot coals or charcoal were placed in the
same position. The cause is very simple. Phosphorus in burning produces
phosphoric acid, which is an anti-combustible, and coats the surface of the paper
round the spot where the combustion occurs, and acting as a kind of glaze or glass,
excludes the oxygen of the air, and prevents the fire spreading.
If some powdered sulphur is sprinkled round the spot where the bit of phosphorus
is to be burnt, the case is very different; the heat melts and sets fire to the sulphur,
which being uncoated with the phosphoric acid, communicates to the paper; and it
is on this principle that lucifer-matches can be used as instantaneous lights. The tip
of the wood of which they are composed is first dipped in sulphur, and then the
phosphorus composition made of gum, chlorate of potash, vermilion, and
phosphorus, is placed over it; and if the latter were used alone without the sulphur,
not one match in a hundred would take fire properly.

Second Experiment.

Common phosphorus is perfectly and rapidly dissolved by bisulphide of carbon.
The solution must be carefully preserved, as it is a liquid combustible, which takes
fire spontaneously after the bisulphide of carbon evaporates; so that wherever it is
dropped, a flame, arising from the spontaneous combustion of the finely-divided
phosphorus, is sure to be produced. This liquid was recommended many years ago
to the Government for the purpose of setting sails of ships or other combustible
matter on fire. The solution of phosphorus alone did not answer the purpose, as
already explained in the first experiment; but when wax was dissolved with the
phosphorus, it then became a most dangerous fluid, which it was recommended
should be used in shells, and discharged from a mortar or howitzer in the ordinary
manner. Dr. Lyon Playfair was the first to make this proposed application of the
solution, and it has since, we believe, been recommended by Captain Norton in his
liquid-fire shells.

Third Experiment.

One of the most curious facts in connexion with phosphorus, is its assumption of
the allotropic state in what is termed amorphous (shapeless) or red phosphorus.
This substance, when handled for the first time, might be mistaken for a lump of
badly-made Venetian red. There is no risk of its taking fire like the common
phosphorus, and it does not (according to Schrötter, of Berlin, who discovered this
peculiar condition) exhale those fumes which are so prejudicial to the lucifer-
match makers. When the vapour of common phosphorus is continually inhaled, it
is said to cause a peculiar and disgusting disease, which terminates in the
destruction of the jaw-bone; whilst the bones in other parts of the body become
brittle, and arm-bones thus affected are fractured with the slightest blow.
The difference between common and red phosphorus is well shown first, by
placing a few small pieces of both kinds in separate bottles or vials containing
bisulphide of carbon; the common phosphorus, as already explained, quickly
dissolves in the liquid, and if poured on a sheet of paper, and hung up, is soon on
fire; whilst the red variety is wholly unaffected, and if the bisulphide of carbon is
poured off on to paper, it merely evaporates, and no combustion occurs.
The similarity in composition, though not in outward form, is further shown by
filling two jars with oxygen gas, and having provided two deflagrating spoons,
some common phosphorus is placed in one, and red phosphorus in the other; a
wire, gently heated by dipping it into some boiling water, is now applied to the
former, which immediately takes fire, and may be plunged into the jar of oxygen
gas, when it burns with the usual brilliancy. The red phosphorus, however, must be
brought to a much higher temperature (500° Fah.) before it will even shine in the
dark, and then with a still further increase of heat it takes fire, and on being placed
in the other jar of oxygen burns up much more slowly than the yellow phosphorus,
but at last exhibits that brilliant flash of light which is so characteristic of the
combustion of phosphorus in oxygen.
The amorphous or red phosphorus is employed in the manufacture of safety
chemical matches, and M. A. Meunons has secured a patent in England for an
improvement in lucifer matches, with a view to obviate the risks of accidental
ignition. To attain this end the matches are first cut by a machine from cubes of
wood, the cut being stopped at a short distance from the end of each cube, so as to
leave the lower extremities adherent. The upper or free extremity of each packet of
splints thus formed being coated with wax or sulphur, is dipped in one of the
following preparations:—Chlorate of potash, two parts; pulverized charcoal, one
part; umber, one part; or, chlorate of potash, sulphur, and umber, in equal parts,

thoroughly mixed with glue. The opposite extremity or "cut" of each packet is then
painted over with amorphous phosphorus blended with size, so that on separating
the matches the phosphorus is only found on the top of each. The matches thus
prepared are ignited by breaking off a small piece of the phosphorised end and
rubbing it on the opposite extremity covered with the inflammable preparation.
Loud exploding and dangerous lucifers were formerly made by dipping bundles of
matches, previously coated with sulphur at the tips, into a thick solution of gum, at
a temperature of 104° Fahr., coloured with smalt or red lead, in which was
dissolved a certain proportion of chlorate of potash, and also containing finely
divided particles of phosphorus obtained by the constant stirring and rubbing of the
materials in a mortar. When dry the matches exploded if rubbed against a gritty
surface, and there was always a risk of a fragment flying off and entering the eye.
To obviate this danger, silent or noiseless lucifer matches were invented, and the
composition used (according to Böttger) is as follows:—Gum arabic, 16 parts by
weight; phosphorus, 9 parts; nitre, 14 parts; powdered black oxide of manganese,
16 parts. The above ingredients are worked up in a mortar with water, at 104°
Fahr., and the matches previously tipped with sulphur are dipped therein and
afterwards dried.

Fourth Experiment.

The combustion of phosphorus under water is easily demonstrated by placing
some ordinary stick phosphorus in a metallic cup, and then plunging it rapidly
under the surface of boiling water. If a jet of oxygen gas is now directed upon the
liquid phosphorus, it burns with great brilliancy. When the oxygen escapes too
rapidly from the jet, it causes some small particles to be thrown out of the water, so
that it is advisable to defend the face with a sheet of wire gauze held a few inches
above the glass whilst the experiment is being conducted. (Fig. 153.)

Fig. 153.
a a. Finger-glass of boiling water containing a metallic cup with melted phosphorus. c. Jet of
oxygen gas. d d. Sheet of wire gauze.

Fifth Experiment.

Phosphorus burns and emits beautiful flashes of light in the presence of the gas
called peroxide of chlorine (ClO4), which must be very carefully generated under
the surface of water by first placing some cut phosphorus and chlorate of potash at
the bottom of a long and stout cylindrical glass nearly full of water; sulphuric acid
is then conveyed to the chlorate of potash by means of a syphon, the end of which
must be drawn out to a small opening, or else the oil of vitriol will descend too
rapidly, and the glass will be cracked by the heat. Immediately the peroxide of
chlorine comes in contact with the phosphorus it explodes, and passes again to its
original elements, oxygen and chlorine. These bubbles envelope minute particles
of phosphorus, which rapidly ascend, like water-spiders, to the surface, and burn as
they pass upwards, producing a continual series of sparks of fire, which have an
extremely pretty effect. (Fig. 154.) The syphon is of course first filled with water,
and as that is displaced, the oil of vitriol takes its place.

Fig. 154.
a a. Tall glass nearly full of water; at the bottom are the chlorate of potash and phosphorus. b.
Wolfe's bottle and syphon, conveying the oil of vitriol to bottom of a a.

Sixth Experiment.

If a little phosphorus is placed in a small copper boiler, and the steam allowed to
escape from a jet, it is observed to be luminous, in consequence of a minute
portion of phosphorus being carried up mechanically with the steam. The same fact
is shown very prettily by boiling water in a flask containing some phosphorus.

Seventh Experiment.

Phosphorus explodes violently when rubbed with a little chlorate of potash, and in
order to perform this experiment safely, it should be made in a strong iron mortar,
the pestle of which must be surrounded with a large circle of cardboard and wire
gauze; so that when it is brought down upon the phosphorus and chlorate of
potash, any particles that may fly out are detained by the shield. Without this
precaution the experiment is one of the most dangerous that can be made. (Fig.
155.)

Fig. 155.
a. The iron mortar containing the phosphorus and chlorate of potash. b. The pestle, with the
shield, c C, composed of a circle of wire gauze, covered with one of cardboard.

Eighth Experiment.

Phosphuretted hydrogen owes its property of spontaneous combustion to the
presence of the vapour of a liquid, phosphide of hydrogen (PH2), which may be
prepared by placing some phosphide of calcium into a flask with water heated to a
temperature of 140° Fah., and conveying the gas into a U-shaped tube surrounded
with a mixture of ice and salt. The liquid obtained is colourless, and must be
preserved from contact with air, as it takes fire spontaneously directly it is exposed
to the atmosphere. (Fig. 156.)

Fig. 156.
a. The flask containing the phosphide of calcium and water, and placed in a water-bath heated
to 140° Fah. b. Bent tube conveying the gas to c c, the U-shaped tube, to which it is attached
by india-rubber tubing, c c. The U-shaped tube, surrounded with a freezing mixture. d d. Bent
tube, passing into a cup of water to prevent contact with air.

Ninth Experiment.

Phosphide of calcium is quickly prepared by placing some small pieces of lime in
a crucible and making them red-hot; if lumps of dry phosphorus are thrown into
the crucible, and the cover placed on quickly, and immediately after the
phosphorus, the latter unites with the calcium, and forms a brown substance which
produces gaseous phosphide of hydrogen (PH3) when placed in water, and the gas
takes fire spontaneously when it comes in contact with the air.

Tenth Experiment.

Phosphorus placed in a retort with a tolerably strong solution of potash, and a
small quantity of ether, affords a large quantity of phosphide of hydrogen
(commonly called phosphuretted hydrogen) when boiled. The neck of the retort
must dip into a basin of water, and the object of the ether is to prevent the
combustion of the first bubbles of gas inside the retort, which by their explosion
would probably break the glass. If the neck of the retort is kept under water in
which potash is dissolved, the gas may be generated for many days at pleasure,
although it is not a desirable experiment to renew too often, on account of the
disagreeable odour produced. (Fig. 157.)

Fig. 157.
A retort containing the phosphorus, water, potash, and ether. b. Neck dipping into a basin of
water. c. The gas burning, and producing beautiful rings of smoke.

Eleventh Experiment.

When a jar of oxygen is held over the neck of the retort generating the
phosphuretted hydrogen, a bright flash of light and explosion are observed; and if
the experiment is performed in a darkened room, it is just like a sudden flash of
lightning. A bottle of chlorine held over the neck of the retort, and dipping of
course in the water of the basin, produces a green flame every time the bubble of
gas passes into it. That curious appearance of light, sometimes seen in marshy
districts, called will-o'-the-wisp, is supposed to be due to the escape, from
decomposing matter, of bubbles of hydrogen, nitrogen, &c., through which the
spontaneously inflammable phosphide of hydrogen is diffused.

At a place called Dead Man's Island, near Sheerness, magnificent effects of this
kind are sometimes apparent when the mud banks are accidentally stirred at night
by a boat-hook. A credible observer says, he once saw there a flash of yellowish-
green light, accompanied with noise, about thirty feet in height. The apparent
height might be due to the duration of the impression of the flash on the eye, as the
light from the burning phosphuretted hydrogen ascended rapidly upwards. The
source of this gas appears to be due to the fact, that during the time some Russian
ships were watched by the Brest fleet, a number of the sailors died of cholera, and
were buried in the banks; the decomposition of the bone containing phosphorus
would account for the appearance of light already described.
With the discussion of some of the most interesting properties of the thirteen non-
metallic elements we take leave of the subject of chemistry, reserving the
consideration of the metals for another popular juvenile work, of which they will
form the subject.
In answer to the oft-repeated question, "Where can I get the things for the
experiments?" it may be stated that every kind of glass vessel and the chemicals
mentioned in this chapter, can be procured either of Messrs. Simpson, Maule, and
Co., Kennington, or of Griffin and Co., Bunhill-row, or Bolton and Co., High
Holborn.

Fig. 158.
Will-o'-the-wisp.

CHAPTER XIII.
FRICTIONAL ELECTRICITY.

Fig. 159.
Franklin and his kite.
Of all the agents with which man is acquainted, not one can afford a greater source
of wonderment to the ignorant, of meditation to the learned, than the effects of that
marvellous force pervading all matter called electricity. We look at matter endowed
with life, and matter wanting this divine gift, with some degree of interest,
depending on our various tastes and occupations; we know at a glance a bird, a
beast, or a fish; we observe with pleasure and admiration the wonderful changes of
nature, and know that a few seeds thrown into the broken clods and well-tilled
earth may become either the waving, golden corn-field or in time may grow from
the tender little shrub to the stately forest-tree; we know all these things because
they belong to the visible world, and are continually passing before our eyes: but
in looking at the visible, we must not forget and ignore the invisible. It may with
truth be stated that the greatest powers of nature are all concealed, and if any truth
would lead us from Nature to Nature's God, it is the fact that no visible, solid,

tangible agent can work with so much force and power as invisible electricity.
Many centuries passed away since the commencement of the Christian era, before
the human mind was prepared to appreciate this great power of nature; other forces
had claimed attention, and the difference in the presence or absence of two of the
imponderable agents, heat and light, as derived from the sun, in the effects of the
change of the seasons, and other common facts, had led philosophers to speculate
early upon their nature; but electricity, from its peculiar properties, long escaped
observation, and it was not until the beginning of the eighteenth century (about
1730) that any material facts had been discovered in this science, when Mr.
Stephen Grey, a pensioner of the Charterhouse, discovered what he termed
electrics and non-electrics, and also the use of insulating materials, such as silk,
resin, glass, hair, &c.; and it is obvious that, until the latter fact was discovered, the
science would remain in abeyance, because there would be no mode of preserving
the electrical excitement in the absence of non-conductors of this force.
The year 1750 was remarkable for Volta's discoveries and Dr. Franklin's
identification of the electricity of the machine with the stupendous effects of the
thunderstorm. Sir Humphry Davy, in 1800, with his commanding genius, threw
fresh light upon the already numerous electrical effects discovered. In 1821,
Faraday commenced his studies in this branch of philosophy; which he has since
so diligently followed up, that he has been for some years, and is still the first
electrician of the age. From the commencement of the present century, discoveries
have succeeded each other in regular order and with the most amazing results; and
now electricity is regularly employed as a money-getting agent in the process of
the electrotype and electro-silvering and gilding; also in the electric telegraph; and
in a few years we may possibly see it commonly employed as a source of artificial
light.
The nature of electricity, says Turner, like that of heat, is at present involved in
obscurity. Both these principles, if really material, are so light, subtle, and diffuse,
that it has hitherto been found impossible to recognise in them the ordinary
characteristics of matter; and therefore electric phenomena may be referred, not to
the agency of a specific substance, but to some property or state of common
matter, just as sound and light are produced by a vibrating medium. But the effects
of electricity are so similar to those of a mechanical agent, it appears so distinctly
to emanate from substances which contain it in excess, and rends asunder all
obstacles in its course so exactly like a body in rapid motion, that the impression of
its existence as a distinct material substance sui generis forces itself irresistibly on
the mind. All nations, accordingly, have spontaneously concurred in regarding
electricity as a material principle; and scientific men give a preference to the same

view, because it offers an easy explanation of phenomena, and suggests a natural
language intelligible to all.
There are five well-ascertained sources of electricity, and three which are
considered to be uncertain. The five sources are friction, chemical action, heat,
magnetism, peculiar animal organisms. The three uncertain sources are contact,
evaporation, and the solar rays.

First Experiment.

A stick of sealing-wax or a bit of glass tube, perfectly dry, rubbed against a warm
piece of flannel, has elicited upon its surface a new power, which will attract bits
of paper, straw, or other light materials; and after these substances are endowed
with the same force, a repellent action takes place, and they fly off. One of the
most convenient arrangements for making experiments with the attractive and
repellent powers of electricity is to fix with shell-lac varnish round discs of gilt
paper, of the size of a half-crown, at each end of a long straw that is supported
about the centre with a silk thread, which may hang from the ceiling or any other
convenient support. (Fig. 160.)
The varnish is easily prepared by placing four or eight ounces of shell-lac in a
bottle, and pouring enough pyroxylic spirit (commonly termed wood naphtha)
upon the lac to cover it. After a short time, and by agitation, solution takes place.
In a variety of ways friction is proved to be a source of electricity, and forms a
distinct branch of the science, under the name of frictional electricity.

Fig. 160.
a. The glass pillar support. b. Straw with discs, hanging by a silk thread.

Second Experiment.

The nature of chemical action has been already explained, and is alluded to here as
a source of electricity of which the proof is very simple. A piece of copper and a
similar-sized plate of zinc have attached to them copper wires; these plates are
placed opposite to, but do not touch each other, in a vessel containing water
acidulated with a small quantity of sulphuric acid. When the wires are brought in
contact, a current of electricity circulates through the arrangement, but has no
power to attract bits of paper, straw, &c. In order to ascertain whether the current
of electricity passes or not, a piece of covered copper wire is bent several times
round a magnetic needle, so that it has freedom of motion inside the core or hollow
formed by twisting the copper wire. This arrangement, properly constructed, is
called the galvanometer needle, and is invaluable as a means of ascertaining the
passage of electricity derived from chemical action. (Fig. 161.)
When the wires leading from the metal plates are connected with the extremities of
the coil in the galvanometer, the needle is deflected or pushed aside to the right
hand or to the left, according to the direction of the current.

Fig. 161.
a. The galvanometer needle. b. Vessel containing weak acid and the zinc and copper plates.
The arrows show the path of the electric current.

Third Experiment.

The third source of electricity is heat, and the effect of this agent is well shown by
twisting together a piece of platinum and silver wire, so as to form one length. If
the silver end is attached to any screw of the galvanometer, and the platinum end

to the second screw, no movement of the magnetic needle takes place until the heat
of a spirit-lamp is applied for a moment to the point of juncture between the silver
and platinum wires, when the magnetic needle is immediately deflected.

Fig. 162.
a. The galvanometer needle, with wires attached. s, s. Silver wire joined to p, p, the platinum
wire. The heat of the spirit-lamp is applied at the point of juncture, +.

Fourth Experiment.

The fourth source of electricity—viz., magnetism—requires a somewhat more
complicated arrangement; and a most delicate galvanometer needle must be
provided, to which is attached the extremities of a long spiral coil of copper wire
covered with cotton or silk. Every time a bar magnet is introduced inside the coil,
so that the conducting wire cuts the magnetic curves, a deflection of the
galvanometer needle takes place, and the same effect is produced on the
withdrawal of the magnet, the needle being deflected in the opposite direction.
The magnetic spark can be obtained by employing a magnet of sufficient power;
and the arrangement for this purpose is very simple. A cylinder of soft iron is
provided, and round its centre are wound a few feet of covered thin copper wire,
one end of which is terminated with a copper disc well amalgamated, and the other
end, after being properly cleaned and coated with mercury, is brought into contact
with the disc. Directly this cylinder is laid across the poles of the magnet, and as
quickly removed, the point and disc, from the elasticity of the former, separate for
the moment, the contact is broken between the point and disc, and a brilliant but
tiny spark is apparent.

Fig. 163.
a b. Horse-shoe magnet. c. Cylinder of soft iron. d. Coil of copper wire and contact breaker.

Fifth Experiment.

The fifth mode of procuring electricity would require the assistance of an electrical
eel, a fine specimen of which (forty inches in length) was exhibited at the Adelaide
Gallery some years ago. Various experiments were made with this animal, and the
author had the pleasure of witnessing all the ordinary phenomena of frictional
electricity, illustrated by Dr. Faraday, with the assistance of the animal electricity
derived from this curious creature. Recent experiments have, however, proved that
the electric current is induced through the agency of the nervous system. This
important fact has been communicated by M. Dubois-Raymond, whose experiment
is thus recorded:—A cylinder of wood is firmly fixed against the edge of a table;
two vessels filled with salt and water are placed on the table, in such a position that
a person grasping the cylinder may, at the same time, insert the fore-finger of each
hand in the water. Each vessel contains a metallic plate, and communicates, by two
wires, with an extremely sensitive galvanometer. In the instrument employed by
M. Dubois-Raymond, the wire is about 3¼ miles in length. The apparatus being
thus arranged, the experimenter grasps the cylinder of wood firmly with both
hands, at the same time dipping the fore-finger of each hand in the saline water.
The needle of the galvanometer remains undisturbed; the electric currents passing
by the nerves of each arm, and being of the same force, neutralize each other. Now,
if the experimenter grasp with energy the cylinder of wood with the right hand, the
left hand remaining relaxed and free, immediately the needle will move from west
to south, and describe an angle of 30°, 40°, and even 50°; on relaxing the grasp,
the needle will return to its original position. The experiment may be reversed by
employing the left arm, and leaving the right arm free: the needle will, in this case,

be deflected from west to north. The reversing of the action of the needle proves
the influence of the nervous force. The conditions, it may be added, essential to the
success of the experiment are: 1st, Great muscular and nervous energy; 2nd, The
contraction of only one arm at a time; 3rd, Dryness and cleanliness of skin; and
4th, Freedom from any kind of wound on the immersed part.

Sixth Experiment.

In making electrical experiments of the simplest kind, it soon becomes apparent
that certain substances, such as glass, sealing-wax, &c., retain the condition of
electrical excitement; whilst other bodies, and especially the metals, seem wholly
incapable of electrical excitation: hence the classification of bodies into conductors
and non-conductors of electricity. This arrangement is not strictly correct, because
no substance can be regarded as absolutely a conductor, or vice versâ. It is better to
consider these terms as meaning the two extremes of a long chain of intermediate
links, which pass by insensible gradations the one into the other. In the
manufacture of electrical apparatus, glass is of course largely employed, and this
substance, with brass and wood, constitute the usual materials. One of the most
instructive pieces of apparatus is the electroscope, which can be made with a gas
jar, a cork, a piece of glass tube, brass wire and ball, or a flat disc of brass, with
some Dutch metal, or still better, gold leaf. The latter is first cut into strips by
retaining the leaf between a sheet of well-glazed paper and cutting through the
paper and the copper or gold leaf, otherwise it would be impossible to cut the
metal, on account of its excessive thinness, except with a gilder's knife and
cushion. The cork is next fitted to the gas jar, and perforated with a hole to admit
the glass tube, which must be thoroughly dry, and is best coated both inside and
out with the shell-lac varnish described at page 175. Some dry silk is wound round
the brass wire, so that it remains fixed and upright in the glass tube, the end outside
the jar having a ball, or still better, a flat disc of brass attached, and the other
extremity being split so as to act like a pair of forceps, to retain a piece of card to
which the gold leaves are attached. By removing the cork, tube, and brass wire
bodily from the neck of the gas jar, and then in a perfectly still atmosphere
carefully bringing the card, slightly wetted with gum at the extremity, on two of
the cut gold leaves, they may be stuck on, and the whole is again arranged inside
the dry gas jar, and forms the important instrument called the electroscope. (Fig.
164.) With the help of this arrangement, a number of highly instructive
experiments are performed.

Fig. 164.
a. The brass wire, with flat disc outside, and forceps holding gold leaf b inside the jar. c c.
The glass tube.

Seventh Experiment.

First, the difference between conductors and non-conductors is admirably shown
by rubbing a bit of sealing-wax against a piece of woollen cloth or flannel; on
bringing the wax to the brass disc of the electroscope the gold leaves no longer
hang quietly side by side, but stand out and repel each other, in obedience to the
law "that bodies similarly electrified repel each other." If the brass cap is touched
whilst the leaves are in this electrical state, they fall again to their original position,
showing that sealing-wax, after being excited, retains its electrical condition, as
also the gold leaves, because they are supported on glass, or what is termed
insulated—i.e., cut off from conducting communication with surrounding objects.
When, however, the sealing-wax is passed through a damp hand, or the brass disc
of the electroscope touched, the electricity is conveyed away to the earth, because
the human body is a conductor of electricity.

Eighth Experiment.

When a brass wire is rubbed and brought to the electroscope, the leaves do not
move, in consequence of the electricity passing away to the earth through the body
as fast as it is generated: it is just like pouring water into a leaky cistern; but if the

brass wire is tied to a long stick of sealing-wax, and this latter held in the hand
whilst the wire is rubbed with a bit of flannel, then the gold leaves of the
electroscope are affected, on account of the insulation of the metal, as every
substance which can be rubbed (even fluids, as water) produces electricity.

Ninth Experiment.

An insulating stool is merely a piece of strong square board, supported on glass
legs, which should be well varnished. If the assistant stands on this stool and
touches the disc of the electroscope, no movement of the leaves takes place until
his coat is briskly struck with a piece of dry silk or skin, when the usual repulsion
occurs.

Fig. 165.
Assistant standing on the insulating stool and touching the disc of the electroscope whilst
being struck with a dry handkerchief.

Tenth Experiment.

If a little powdered chalk is placed inside a pair of bellows, and then forcibly
ejected on to the disc of the electroscope, the friction of the particles of chalk
against the inside of the nozzle of the bellows and against the disc of the
instrument soon liberates sufficient electricity to cause the gold leaves to stand out
and repel each other.

Eleventh Experiment.

Whilst the leaves of the electroscope are repelled from each other by the
application of a bit of rubbed sealing-wax, they may be again caused to approach
each other on bringing a dry glass tube previously rubbed with a silk-handkerchief;
because the electricity obtained from sealing-wax is different from that procured
from glass: the former is called resinous or negative electricity, the latter positive
or vitreous electricity. Either, separately, is repulsive of its own particles, but
attractive of the other. No electrical excitation can occur without the separation of
these two curious states of electricity, and electrical quiescence takes place when
the two electricities are brought together; hence the fall of the gold leaves repelled
by rubbed wax when the excited glass is brought towards the disc of the
electroscope. This experiment may be reversed by repelling the leaves first with
the excited glass, and then bringing the rubbed wax, when the same effect takes
place.

Twelfth Experiment.

To show the important elementary truth, that in all cases of electrical excitation the
two kinds of electricity are generated, take a dry roll of flannel, and holding it as
lightly as possible, rub it against a bit of wax. If the flannel is brought to the
electroscope, the leaves repel each other, and they immediately fall when the wax
is now approached, because the flannel is in the positive or vitreous state of
electricity, whilst the sealing-wax is in the negative or resinous condition.

Thirteenth Experiment.

Any kind of friction generates electricity. A little roll brimstone placed in a dry
mortar and powdered, and then thrown on to the electroscope, quickly causes the
repulsion of the leaves.

Fourteenth Experiment.

A sheet of dry brown paper laid on a flat surface, and vigorously rubbed with a
piece of india-rubber, produces so much electricity that sparks and flashes of light
are apparent in a dark room when it is lifted from the table; and it affects the leaves
of the electroscope very powerfully, so much so that care must be taken to apply it
very carefully to the disc, or the violence of the repulsion may cause the fracture of

the gold leaves, and then a great deal of time is wasted before they can be put on
again.

Fifteenth Experiment.

A dry wig or bunch of horse-hair when combed becomes electrical, and likewise
affects the leaves of the electroscope.

Sixteenth Experiment.

Two dry silk ribbons, the one white and the other black, passed rapidly together
through the fingers, exhibit sparks and flashes of light when drawn asunder, and
also cause the gold leaves to repel each other.

Seventeenth Experiment.

Much instructive amusement is afforded by testing the gold leaves when separated
from each other during either of the former experiments, with an excited piece of
sealing-wax. If the electricity produced is negative, they repel each other further
when the excited wax is approached; if positive, they fall when the excited wax is
brought near them.

Eighteenth Experiment.

When fresh, dry, ground coffee is received on to the disc of the electroscope, as it
falls from the mill, powerful electrical excitation is displayed, and this is
sometimes so apparent, that the particles cling around the lower part of the mill or
to the sides of the cup or basin held to catch it.

Nineteenth Experiment.

After playing a tune on a violin, hold the bow (well rosined) to the electroscope,
when the usual divergence of the leaves will be apparent.

Twentieth Experiment.

Cut some chips from a piece of wood with a knife attached to a glass handle, and
as they fall on to the electroscope the leaves are repelled.

Twenty-first Experiment.

Warm a piece of bombazine by the fire and then draw out some of the threads
(which are of two kinds—viz., silk and wool), and place them on the electroscope,
when divergence of the leaves immediately takes place.

Twenty-second Experiment.

Put upon the same leg a worsted stocking and over that a silk one, if the latter is
now quickly rubbed all over with a dry hand and near the fire, and then suddenly
slipped off, the sides repel each other, and the silk stocking retains very much the
same shape as if the leg still remained in it, and of course collapses as the
electricity passes away.

Twenty-third Experiment.

Electrical machines consist only in the better arrangement of larger pieces of glass
and a more convenient mechanical contrivance for rubbing them, and are of two
kinds—viz., the cylinder and plate machines; it is usual to give directions for the
manufacture of an electrical machine from a common bottle, and doubtless such
rude instruments have been made, but as Messrs. Elliott Brothers, of 30, Strand,
now supply excellent small machines at a very low cost, it is hardly worth while to
incur even a small expense for an instrument that must at the best be a very
imperfect one and frequently out of order. (Fig. 166.)

Fig. 166.
A cylinder electrical machine.

Plate machines are somewhat more expensive than cylinder ones, but at the same
time are more quickly prepared for experiments, and Mr. Hearder, of Plymouth,
states, that the secret in obtaining the greatest amount of electricity from a cylinder
machine, is to keep the inside of the glass absolutely clean, dry, and free from dust.
Sometimes the glass of which electrical machines are made is wholly unfit for
electrical purposes, in consequence of the decomposition of the surface from
imperfect manufacture and the liberation of the alkali. (Figs. 167, 168.)

Fig. 167. Fig. 168.
Woodward's double plate electrical machine, giving a
The ordinary plate electrical machine.
much larger quantity of electricity than Fig. 167.

Twenty-fourth Experiment.

Cylinder and plate machines are furnished with proper rubbers, and before using
the instrument it is usual to remove them, and after carefully cleaning the glass
with a dry silk handkerchief before a fire, the rubbers are scraped with a paper-
knife to remove the old amalgam, and fresh applied by first melting the end of a
tallow candle slightly, and after passing this over the rubber, the finely powdered
amalgam is now dusted on to it. Electrical amalgam is prepared by fusing one part
of zinc with one of tin, and then agitating the liquid mass with two parts of hot
mercury placed in a wooden box; when cold it should be carefully powdered and
kept in a well-stoppered bottle for use. When the amalgam has been applied, the
rubbers are again screwed in their places, and the machine when turned (if the
atmosphere is tolerably dry) will emit an abundance of bright sparks.

Twenty-fifth Experiment.

Attraction and repulsion are shown on a larger scale, with the assistance of
electrical machines, by placing a fishing rod (the last joint of which is made of
glass) in an erect position, and attaching to the extremity a long tassel of paper
from which a thin wire passes to the prime conductor of the electrical machine; on
turning the instrument, the strips of paper all stand out and repel each other. (Fig.
169.)

Fig. 169.
a a. The glass joint of the fishing-rod, from which the last joint, carrying the paper tassel, b,
projects. c. The electrical machine.

Twenty-sixth Experiment.

Suspend from the prime conductor by a chain a circular brass plate and under this
place another supported by a brass adjusting stand. If pith figures of men and
women are placed on the lower plate, they rise directly the machine is turned,
although sometimes, in consequence of irregularity in the adjustment of the centre
of gravity, they perversely dance on their heads instead of the usual position; out of
half a dozen figures, one only perhaps will be found to dance well, by alternately
jumping to the upper plate and falling to the lower one to discharge the excess of
electricity; and indeed the experiment will be found to succeed better with one or
two only on the plate instead of a number, as they cling together and impede each
other's movements. (Fig. 170.)

Fig. 170.
a. Prime conductor. b. Upper brass-plate. c. Lower ditto. The figures are seen between b and
c.

Twenty-seventh Experiment.

An assistant provided with a wig of well-combed hair presents a most ridiculous
appearance when standing on the insulating stool and connected by a wire with the
prime conductor of the electrical machine, every hair, when not matted together,
standing out in the most absurd manner, when the machine is put in motion.

Twenty-eighth Experiment.

Whilst standing on the stool, sparks may be obtained from his body, and if some
tow is tied over a brass ball, and moistened with a little ether, and presented to the
tip of his finger, a spark flies off which quickly sets fire to the inflammable liquid.

Twenty-ninth Experiment.

If small discs of tinfoil, cut out with a proper stamp, are pasted in continuous lines
over plate glass, or spirally round glass tubes, a very pretty effect is produced
when they receive the sparks from the electrical machine, and the passage of the
electricity from one disc to the other produces a vivid spiral or other line of light.
When the tube is mounted in a proper apparatus, so as to revolve whilst the sparks

pass down the spiral tube, the effect of the continuous electric sparks is much
heightened. (Fig. 171.)

Fig. 171.
a a a. A ring of brass wire supported on a glass pillar inside which the spiral tube, b, revolves,
and produces beautiful and ever-changing circles of light, when connected with the conductor,
c, of the electrical machine.

Thirtieth Experiment.

A great variety of experiments, depending on the proper arrangement of discs of
tinfoil on various tubes of coloured glass are manufactured, and some in the form
of windmills, the sails being made luminous by the passage of the electricity. The
names of illustrious electricians, beautiful crescents, stars, and even profile
portraits, have been produced in continuous streams of electric sparks.

Thirty-first Experiment.

When an electrified body is brought towards another which is not electrical, the
latter is thrown into the opposite state of electricity as long as the excited body
remains in its neighbourhood; and this condition of electrical disturbance, set up
without any contact or supply of electricity, is called induction, and involves a vast
number of interesting facts, which are thoroughly discussed in Dr. Noad's excellent
work on electricity, but can only be briefly alluded to here.

If a number of lengths of brass wire, supplied with balls at the extremities, are
supported on glass legs and arranged in a line, with a little pith ball attached to a
thread hanging from each end of the length of brass wire, the effect of induction is
shown very nicely; and when an excited glass rod is brought towards one end of
the series, the rising of the pith balls to each other betrays the change which has
occurred in the electrical state of the brass wires by the mere neighbourhood of the
excited glass tube. The glass tube is electrified positively, and attracts the negative
electricity from the brass wire towards the end nearest to it; the other extremity of
the brass wire is found to be in the positive state, and this re-acting on the next,
and so on throughout the lengths, completes the electrical disturbance in the whole
series. (Fig. 172.)

Fig. 172.
The lengths of brass wire supported on glass rod pillars indented by blowpipe, so as to retain
the brass wires with the pith balls hanging from each series, the letters p and n mean Positive
and Negative, and the signs for these terms are placed above. The letters p and n are painted
on the blocks which support the glass rods.

Thirty-second Experiment.

If an insulated brass rod (such as has been described in the last experiment) is
touched by the finger whilst under induction, it remains permanently electrified on
the removal of the disturbing electrified body; and it is on this principle that the
useful electrical machine called the Electrophorus is constructed. This constant
electrical machine—for it will remain in action during weeks and months if kept
sufficiently dry—was invented by Volta in the year 1774, and has been brought to
great perfection by Mr. Lewis M. Stuart, of the City of London School; so that
with a little additional apparatus the whole of the fundamental principles of
electricity can be demonstrated. It consists of a flat brass or tin circular dish about
two feet in diameter and half an inch deep, which is filled with a composition of
equal parts of black rosin, shell-lac, and Venice turpentine; the rosin and the Venice
turpentine being first melted together, and the shell-lac added afterwards, care of
course being taken that the materials do not boil over and catch fire, in which case

the pot must be removed from the heat, and a piece of wet baize or other woollen
material thrown over it. Another tin or brass circular plate of twelve inches
diameter, and supported in the centre with a varnished glass handle nine inches
long, is also provided, and the resinous plate being first excited by several smart
blows with a warm roll of flannel, the plate held by the glass handle is now laid
upon the centre of the resinous one, and if removed directly afterwards, does not
afford the electric spark; but if, whilst standing upon the excited resinous plate, it
is touched, and then removed by the glass handle, a powerful electric spark is
obtained; and this may be repeated over and over again with the like results,
provided the plate with the glass handle is touched with the finger just before
lifting it from the resinous plate. (Fig. 173.) The electricity excited on the resinous
plate is not lost, and by induction sets up the opposite condition in the plate with
the glass handle. The resinous plate, being excited with negative electricity,
disturbs the electrical quiescence of the upper plate, and positive electricity is
found on the surface touching the resinous plate, and negative electricity on the
upper one, so that when it is removed without being touched, the two electricities
come together again, and no spark is obtained; but if, as already described, the
upper plate is touched whilst under induction, then positive electricity appears to
pass from the finger to the negative electricity on the upper side of the plate, when
the two temporarily neutralize each other, and then, when the plate is removed, the
excess of electricity derived from the earth through the finger becomes apparent.
Induction requires no sensible thickness in the conductors, and can be just as well
produced on a leaf of gold as on the thickest plate of metal; and it should be
remembered that non-conductors do not retain their state of electrical excitation
when the disturbing cause is removed, whereas conductors possess this power, and
this fact brings us to the consideration of the Leyden jar.

Fig. 173.

a a. Large circular tin or brass disc with turned-up edge half an inch deep, and containing the
resinous mixture b, which is rubbed with the warm flannel. c c. The upper plate supported by
the glass handle d, a pith ball attached to a wire shows the electrical excitation, and the spark
is supposed to be passing to the hand e.

Thirty-third Experiment.

If one side of a dry glass plate is held before and touches a brass ball proceeding
from the prime conductor of an electrical machine whilst in action, the other side is
soon found to be electrical; this does not arise from the conduction of the
electricity through the particles of the glass, but is produced by induction, the side
nearest the ball being in the positive state, and the other side negative: as glass is a
non-conductor of electricity, the effect is much increased by coating each side with
tinfoil, leaving a margin of about two inches of uncovered glass round the covered
portion, then, if one side of such a plate is held to the prime conductor of the
electrical machine, and the other connected with the ground, a powerful charge is
accumulated; and if the opposite sides are brought in contact with a bent brass
wire, a loud snapping noise is heard, and the two electricities resident on either
side of the glass come together with the production of a brilliant spark, or if the
hands are substituted for the bent brass wire, that most disagreeable result is
obtained—viz., an electric shock; hence these glass plates are sometimes fitted up
as pictures, and when charged and handed to the unsuspecting recipient, he or she
receives the electric discharge to the great discomfort of their nervous system.
Mica is sometimes substituted for glass, and the late Mr. Crosse, the celebrated
electrician, constructed a powerful combination of coated plates of this mineral. It
consisted of seventeen plates of thin mica, each five inches by four, coated on both
sides with tinfoil within half an inch of the edge. They were arranged in a box with
a glass plate between each mica plate, all the upper sides were connected by strips
of tinfoil to one side of the box, and all the under surfaces in the same manner with
the opposite extremity of the box. They were charged like an ordinary Leyden
battery.

Thirty-fourth Experiment.

If the glass plate coated with tinfoil is charged, and then placed upright on a stand,
it may be slowly discharged by placing a bent wire on the edge with the
extremities covered with pith balls. The wire balances itself, and continues to
oscillate with noise until the electricities of the two surfaces neutralize each other.
(Fig. 174.)

Fig. 174.
a a. Glass plate or stand coated with tinfoil on each side, b. c. Wire with pith balls oscillating
during the discharge of the glass plate.

Thirty-fifth Experiment.

It is easy to imagine the glass plate of the last experiment rolled up into the more
convenient form of the Leyden jar, which consists of a glass vessel lined both
inside and out with tinfoil, leaving some two or three inches of the glass round the
mouth uncovered and varnished with shell-lac; a piece of dry wood is fitted into
the mouth of the jar, through which a brass wire and chain are passed, and the end
outside is fitted with a ball. The Leyden jar is charged by holding the ball to the
prime conductor of the electrical machine until a sort of whizzing noise is heard,
caused by the excess of electricity passing round the uncovered part of the jar and
not through it, as the smallest crack in the glass of the Leyden jar would render it
useless. Electricity is sometimes called a fluid, and the fact of collecting it like
water in a jar, helps us to understand this analogy. The noise, the bright spark, or
the shock are obtained by grasping the outside with one hand and touching the ball
with a brass wire held in the other. (Fig. 175.)

Fig. 175.
The Leyden jar and brass wire discharger.

Thirty-sixth Experiment.

The jar is silently discharged if the balls are removed from the discharger and
points used instead; so, also, the whole of the electricity produced by an electrical
machine in full action may be readily drawn off by a pointed conductor, such as a
needle, placed at the end of a brass wire. Electricity passes much more rapidly
through points than rounded surfaces, hence the reason why all parts of electrical
apparatus are free from sharp points and rough asperities.

Thirty-seventh Experiment.

Extremely thin wires may be burnt by passing the charge of a large Leyden jar
through them. The show jars, called specie jars, usually decorated and placed in
the windows of chemists' shops, make excellent Leyden jars, when not too thick;
and with two of the largest, all the interesting effects produced by accumulated
electricity may be displayed. To pass the discharge through wires, nothing more is
required than to strain them across a dry mahogany board, between two brass wires
and balls, and if a sheet of white paper is placed under them, most curious
markings are produced by the fine particles of the deflagrated metal blown into the
surface of the paper. An arrangement of two or more Leyden jars is usually called a
Leyden Battery, just as a single cannon is spoken of as a gun, whilst two or more
constitute a battery. (Fig. 176.)

Fig. 176.
a. Mahogany board with a sheet of white paper and three pairs of brass wires and balls fixed
in the wire, three on each side. The thin wires are stretched between the balls, and the lower
one is in course of deflagration. b b. Charged large Leyden battery of two jars; the arrows
indicate the path of the electricity.

Thirty-eighth Experiment.

Little models of houses, masts of ships, trees, and towers are sold by the
instrument makers, and by placing a long balanced wire on the top of the pointed
wire of a large Leyden jar, having one end furnished with wool to represent a
cloud, a most excellent imitation of the effects of a charged thunder-cloud is
produced. The mechanical effect of a flash of lightning has been analysed, and it
has been stated, in one instance, that the power developed through fifty feet was
equal to a 12,220 horse-power engine, or about the power of the engines of the
Great Eastern, and that the explosive power was equal to a pressure of three
hundred millions of tons. (Fig. 177.)

Fig. 177.
A. Charged Leyden jar with balanced wire and wool at B, representing a thunder-cloud. C.
The obelisk overturned with the discharge. D. Another model of the gable end of a house; the
square pieces of wood fly out when the continuity of the conductor is broken.

It was the learned but humble minded Dr. Franklin who established the identity
between the mimic effects of the electrical machines (such as have been
described), and the awe-inspiring thunder and lightning of nature. A copper rod,
half an inch thick, pointed and gilt at the extremity, and carried to the highest point
of a building, will protect a circle with a radius of twice its length. The bottom of
the rod must be passed into the earth till it touches a damp stratum.

Fig. 178.

A storm.

CHAPTER XIV.
VOLTAIC ELECTRICITY.

In describing the various means by which electricity may be obtained, it was stated
that "Chemical Action" was a most important source of this remarkable agent; at
the same time it must be understood that it is not every kind of chemical action
which is adapted for the purpose; there are certain principles to be rigidly adhered
to—first, in the generation of the force; and secondly, in carrying it by wires so as
to be applicable either for telegraphic purposes, or for the highly valuable
processes of electrotyping and electro-silvering, plating, and gilding.
A lighted candle, or an intense combustion of coal, coke, or charcoal, no doubt
involves the production of electricity, but there are no means at present known by
which it may be collected and conducted; when that problem is solved, the
cheapest voltaic battery will have been constructed, in which the element
decomposed is charcoal, and not a metal, such as iron or zinc. The first and most
simple experiment that can be adduced in proof of electrical excitation by chemical
means, is to take a bit of clean zinc and a clean half-crown, and placing one on the
tongue and the other below it, as long as they remain separate no effect is
observed, but directly they are made to touch each other, whilst in that position, a
peculiar thrill is rendered evident by the nerves of the tongue, which in this case
answers the same purpose as the electroscope already described, and in a short
time a peculiar metallic taste is perceptible.
It has been stated over and over again that it was to a somewhat similar
circumstance we owe the discovery of voltaic electricity, and the story of the
skinned frogs agitated and convulsed by an accidental communication with two
different metals, or, as some say, with the electricity from an ordinary machine, has
been repeated in nearly every work on the science. Professor Silliman, however,
asserts that the galvanic story is doubtful, and is a fabrication of Alibert, an Italian
writer of no repute, and that greater merit is due to Galvani than that of being
merely the accidental discoverer of this kind of electricity, because he had been
engaged for eleven years in electro-physiological experiments, using frogs' legs as
electroscopes. It was whilst experimenting on animal irritability, Galvani noticed
the important fact that when the nerve of a dead frog, recently killed, was touched
with a steel needle, and the muscle with a silver one, no convulsions of the limb
were produced until the two different metals were brought in contact, and he

explained the cause of these singular after-death contortions by supposing that the
nerves and muscles of all animals were in opposite states of electricity, and that
these nervous contractions were caused by the annihilation, for the time, of this
condition, by the interposition of a good conductor between them.
This theory of Galvani had several opponents, one of whom, the celebrated Volta,
succeeded in pointing out its fallacy; he maintained that the electrical excitement
was due entirely to the metals, and that the muscular contractions were caused by
the electricity thus developed passing along the nerves and muscles of the dead
animal.
To Volta we are indebted for the first voltaic battery, and the distinguished
philosopher may truly be said to have laid the foundation of this now commercially
valuable branch of science.

First Experiment.

If a plate of clean bright zinc is placed in a vessel containing some dilute sulphuric
acid, energetic action occurs from the oxidation of the metal, and its union as an
oxide with the acid, and the escape of a multitude of bubbles of hydrogen gas.
After the action has proceeded some time, the zinc may be removed, and if a little
quicksilver is now rubbed over the surface with a woollen rag tied on the end of a
stick, it unites with the metal, and the surface of the zinc assumes a brilliant silvery
appearance, and is said to be amalgamated. In that condition it is no longer acted
upon by dilute sulphuric acid, and for the sake of economy this is the only form in
which zinc should be employed in the construction of voltaic batteries or single
circles. If a clean plate of copper, with a wire attached, is now placed in the dilute
acid opposite to and not touching the amalgamated zinc plate, which may also be
furnished with a conducting wire, no bubbles of hydrogen escape until the wires
from the two metals are brought in contact, and then, singular to relate, the
hydrogen escapes from the copper plate, whilst the oxygen is rapidly absorbed by
the zinc, and a current of electricity will now be found to pass from the zinc
through the fluid to the copper, and back again through the wire to the starting
point, and if the wires are disconnected, the chemical action ceases, and no more
electricity is produced. (Fig. 179.)

Fig. 179.
A single voltaic circle, consisting of a zinc and copper plate (marked z and c) in dilute acid.
The arrows show the direction of the current.

The passage of the current of electricity is not discoverable by the electroscope,
because it is adapted only to indicate electricity of high tension or intensity, such
as that produced from the electrical machine, which will pass rapidly through a
certain thickness of air, and cause pith balls to stand out and repel each other; such
effects are not producible by a single voltaic circle, or even an ordinary voltaic
battery, although one comprising some hundreds of alternations would produce an
effect on a delicate electrometer; hence voltaic electricity is said to be of low
intensity, and this property makes it much more useful to mankind, because it has
no desire to leave a metallic path prepared for it, and does not seize the first
opportunity, like the electricity from the electrical machine, to run away to the
earth through the best and shortest conductor offered for it. If electricity had only
been producible by friction, we should never have heard of electrotyping, and the
other useful applications of electrical force of low intensity.

Second Experiment.

To ascertain the passage of a current of voltaic electricity, the instrument called the
galvanometer needle is provided, which consists of a coil of copper wire
surrounding a magnetic needle, so as to leave the latter freedom of motion from
right to left, or vice versá. When this coil is made part of the voltaic circle it
becomes magnetic, and reacting on the magnetized needle, deflects it to one side
or the other, according to the direction of the current. (Fig. 180.)

Fig. 180.
A galvanometer needle, consisting of a coil of covered copper wire, the ends of which
terminate at the binding screws. The magnetic needle is suspended on a point in the centre,
and the coil is surrounded with a graduated circle.

Third Experiment.

If a number of simple voltaic circles, such as the one described in the first
experiment, are connected together, they form a voltaic battery, in which of course
the quantity of electricity is greatly increased. Batteries of all kinds, from the
original Volta's pile, consisting of round zinc and copper plates soldered together
with interposed cloth moistened with dilute sulphuric acid, or his couronne des
tasses, consisting of zinc and silver wires soldered together in pairs, and placed in
glass cups containing dilute acid, to the improved batteries of Cruikshank,
Wilkinson, Babington, Wollaston, and the still more perfect arrangements of
Daniell, Mullins, Shillibeer, and Grove, have been from time to time recommended
for their own peculiar features.
Amongst these several inventions, none will be found more useful than the
constant battery of Daniell for electrotyping, silvering, gilding, and other purposes,
and Grove's battery for all the more brilliant results, such as the deflagration of the
metals or the production of the electric light. The construction of the Daniell and
Grove batteries will therefore be described. The former consists of a cylindrical
vessel made of copper, in which is suspended or placed (as it is open at the top) a
membranous, brown-paper, canvas, or porous earthenware tube, containing an
amalgamated rod of zinc. To charge this arrangement, a strong solution of sulphate
of copper, with some sulphuric acid, is poured into the copper vessel, which is
provided usually with a sort of colander at the top to hold crystals of sulphate of
copper, and in the porous tube containing the zinc rod is poured dilute sulphuric
acid. A number of these cylinders of copper, twenty inches high and three inches
and a half in diameter, arranged in wooden frames to the number of twenty, afford
a quantity of electricity sufficient to demonstrate all the usual phenomena. (Fig.
181.)

Fig. 181.
a a. Copper cylindrical vessel with colander to hold the crystals of sulphate of copper. b. The
amalgamated zinc rod inside the porous cell c c. d. A series of single cells forming a Daniell's
battery.

Professor Grove's battery consists of a flat glazed earthenware vessel containing a
flat porous cell. An amalgamated zinc plate is placed outside the porous cell, and a
platinum plate inside the latter. The arrangement is put in action by pouring dilute
sulphuric acid round the zinc and strong nitric acid inside the porous cell. A set of
Grove's nitric acid battery, as manufactured by Messrs. Elliott, Brothers, of 30,
Strand, with fifty pairs of sheet platinum, five inches by two inches and a quarter,
and double amalgamated zinc plates, flat porous cells, and separate earthenware
troughs for each pair, and stout mahogany stand, arranged in ten series of five
pairs, will evolve with a proper voltameter one hundred cubic inches of the mixed
gases per minute from the decomposition of water, and will exhibit a most brilliant
electric light, when arranged as a single series of fifty pairs of plates. Even thirty
pairs exhibit the most splendid effects, whilst forty may be regarded as the happy
medium, giving all the results that can be desired. (Fig. 182.)
The advantage of employing amalgamated zinc is very prominently illustrated
whilst using any powerful arrangements of either Daniell's or Grove's batteries, as
they will remain for hours quiescent, like a giant asleep, until the terminal wires of
the series are brought in contact either through the intervention of some fluid under
decomposition or by means of charcoal points. The author had the pleasure of
witnessing at King's College some of the effects of an enormous battery, prepared
by the late Professor Daniell, and consisting of seventy of his cells.

Fig. 182.
a a. Amalgamated zinc plate in flat earthenware trough. Attached to a binding screw is the
platinum plate in porous cell, c c. d. A series of single cells forming a Grove's battery.

A continuous arch of flame was produced between two charcoal points, when
distant from each other three quarters of an inch, and the light and heat were so
intense that the professor's face became scorched and inflamed, as if it had been
exposed to a summer heat. The rays collected by a lens quickly fired paper held in
the focus.[C]
[C] By the light from the same battery photogenic drawings were taken, and the heating
power was so great as to fuse with the utmost readiness a bar of platinum one-eighth of
an inch square; and all the more infusible metals, such as rhodium, iridium, titanium,
&c., were melted like wax when placed in small cavities in hard graphite and exposed to
the current of electricity.

Fourth Experiment.

It is by "chemical action" the electricity is produced, and as action and reaction are
always equal, but contrary, we are not surprised to find that the electricity from the
voltaic battery will in its turn decompose chemically many compound bodies, of
which water is one of the most interesting examples. It was in the year 1800, and
immediately after Volta's announcement to Sir Joseph Banks of his discovery of
the pile, that Messrs. Nicholson and Carlisle constructed the first pile in England,
consisting of thirty-six half-crowns, with as many discs of zinc and pasteboard
soaked in salt water. These gentlemen, whilst experimenting with the pile,
observed that bubbles of gas escaped from the platinum wires immersed in water
and connected with the extremities of the Volta's pile, and covering the wires with
a glass tube full of water, on the 2nd of May, 1800, they completed the splendid

discovery of the fact that the Volta's current had the power to decompose water and
other chemical compounds.
In 1801, Davy had succeeded to a vacant post in the Royal Institution, and on Oct.
6th, 1807, made his transcendent discovery of potassium with the aid of the voltaic
battery, and from that and other experiments inferred that the whole crust of the
globe was composed of the oxides of metals. To exhibit the decomposition of
water, two platinum plates with proper connecting wires, passing to small metallic
cups full of mercury, are cemented inside a glass vessel, which is then filled with
dilute sulphuric acid. Just above the platinum plates and over them, stand two glass
tubes also containing the same fluid in contact with the battery. Two measures of
hydrogen are found in one tube, and one of oxygen in the other. (Fig. 183.)

Fig. 183.
a a. A finger glass with two holes drilled to pass the wires through, which are imbedded in
cement up to the platinum plates. b b. Glass tubes, closed at one end and open at the other,
which are placed over the platinum plates to receive the liberated oxygen and hydrogen. The
scale at the side shows the respective volumes of two of H to one of O.

To measure the quantity power of the voltaic battery, an important instrument
invented by Faraday is used. It consists of separate platinum plates cemented in a
wooden stand, and over which a capped air-jar with a bent pipe is also cemented.
This apparatus contains dilute sulphuric acid of the same strength as that used in
the battery under examination, and by taking the time, the quantity of the mixed
oxygen and hydrogen gases producible by a battery per minute is accurately
determined, the gases of course being collected in a graduated jar. (Fig. 184.)

Fig. 184.
a. Gas jar with cap and bent tube passing to the graduated tube c; the jar is cemented in the
same stand which carries the connecting cups, wires, and platinum plates, which are bent
round each other to improve the action of the voltameter.

Fifth Experiment.

By grouping the simple circles forming a voltaic battery in various numerical
relations, the quantity and intensity effects are modified.
Thus, if a series of thirty pairs of Grove's battery are all connected together in
consecutive order, the smallest quantity and the largest intensity effect is produced.
If changed to two groups of fifteen each, the quantity is doubled—that is to say, it
will produce double the quantity of the mixed gases from the voltameter with half
the intensity.
If arranged in three groups of ten each, it is trebled with a proportional loss of
intensity, until the grouping reaches six series of five each, when a maximum
supply of the mixed gases is obtained from the voltameter.
In arranging the groups, all the zinc ends of each series are connected, and all the
platinum ends are likewise joined by proper wires.

Sixth Experiment.

A plate-glass trough, containing a few grains of iodide of potassium dissolved in
water with some starch, is quickly decomposed into its elements by placing in two
platinum plates and connecting them with the wires of the voltaic battery. If the

glass trough is divided in the centre with a bit of cardboard, the purple colour of
the iodine and starch is shown very beautifully on one side, but not on the other, as
iodine is liberated at one pole and the alkali at the other. (Fig. 185.)

Fig. 185.
a a. A glass trough containing the salt dissolved in water, and divided temporarily with a bit
of cardboard, b. c c are the two platinum plates connected with the battery, and the shaded
side is supposed to represent the liberation of the iodine.

Seventh Experiment.

Some solution of common salt coloured with sulphate of indigo and placed in the
trough is decomposed into chlorine, which bleaches one side of the indigo
solution, and the alkali liberated on the other does not affect it.

Eighth Experiment.

Some nitrate of potash dissolved in water and coloured with litmus placed in the
glass trough, changes red on one side of the cardboard by the liberation of acid,
and is not affected on the other.
In these experiments the oxygen, iodine, chlorine, and nitric acid are liberated at
the electro-positive pole, and are hence termed electro-negative bodies, whilst
hydrogen and the alkalies are set free at the electro-negative pole, and are therefore
called electro-positive bodies. Faraday has modified these terms, and calls the two
classes "anions" and "cathions," and the two poles "anodes" and "cathodes."
Anode, from ανα, up, and ὁδος, a way: the way which the sun rises. Anions, from
ανα, up, and ειμι, to go: that which goes up; a substance which passes to the anode

during the passage of a current of electricity. Cathode, from κατα, down, and ὁδος,
a way: the way which the sun sets. Cathion, from κατα, down, and ειμι, to go: that
which goes down; a substance which passes to the cathode during the passage of
electricity from the anode to the cathode.

Ninth Experiment.

In the process of the electrotype is presented a valuable application of the chemical
power of the voltaic circle or battery, and it may be conducted either as a single
cell operation or by distinct batteries. In the former case the most simple
arrangement will suffice; the only articles necessary are—a large mug or tumbler;
some brown paper and a ruler; a bit of amalgamated zinc, four inches long and half
an inch wide; a short length of copper wire; some black lead, blue vitriol, and oil
of vitriol.
The mould from which the electrotype is to be taken can be made of common
sealing wax, plaster of Paris, white wax, gutta percha, or fusible alloy. Supposing
the first to be selected—viz., a common seal, it is first thoroughly black-leaded,[D]
then one end of the copper wire is bent round the top of the amalgamated zinc, and
the other is gently warmed and melted into the side of the seal, leaving a small
portion uncovered by the wax, which is then well black-leaded. A few ounces of
blue vitriol are dissolved in boiling water, and when cold the solution is poured
into the tumbler, and the porous cell to contain the mixture of eight parts water to
one of sulphuric acid is made by rolling the brown paper three or four times round
the ruler and closing the end, and fixing the side with a little sealing wax. The
porous cell of brown paper is now filled with the dilute acid, and placed in the
tumbler containing the solution of blue vitriol, the amalgamated zinc being
arranged in the paper cell, and the attached seal in the copper solution; in about
twelve hours a good deposit of copper is produced, and a perfect cast in metal of
the seal obtained. (Fig. 186.)
[D] The application of plumbago, or black lead, for electrotype purposes, was first made
by the late lamented Mr. Robert Murray.

Fig. 186.
a a. The tumbler containing the solution of sulphate of copper. b b. The brown paper cell
containing the dilute sulphuric acid, inside which is the amalgamated zinc with wire attached
to the seal d.

Messrs. Elliott provide every kind of convenient vessel for the purpose, and in the
picture below it will be noticed that the single cell apparatus, though not so
economical as the simple tumbler arrangement already described, is perhaps more
convenient for electrotyping. (Fig. 187.)

Fig. 187.
a. Single cell apparatus with proper vessel, porous tube, and binding screws. b. A large trough
divided by a diaphragm of biscuit-ware or very thin porous wood.

Tenth Experiment.

A single cell apparatus is only adapted to produce small electrotypes, but when
larger ones are required, a separate battery of three or four Daniell's or Smee's cells
is required; and it is usual to place the mould to be copied in a separate wooden
trough, attaching it to the cathode wire, whilst a copper plate is connected with the
anode, so that as the solution of sulphate of copper undergoes decomposition by
the passage of the electricity, it is kept almost in a normal state, in consequence of
the oxygen of the water and the acid passing to the copper plate, which they attack
and dissolve as fast as the oxide of copper and hydrogen are liberated at the
cathode, where the latter deoxidizes the oxide of copper, and by a secondary action
deposits metallic copper; the object being to dissolve fresh metal as the copper is
deposited on the mould. (Fig. 188.)

Fig. 188.
a. A single cell, Daniell's, attached to b, the trough containing the mould and the plate of
copper. Below is a Smee's battery ready to be attached to a larger trough for the purpose of
electrotyping a great number of moulds at the same time.

Eleventh Experiment.

To silver electrotypes or other brass and copper articles, the first attention must
be paid to the cleanness of them; and when an electrotype is just removed from
the copper solution, and washed in clean water, it is at once ready to receive the
coating of silver; otherwise, if it has been handled, or is slightly greasy, it should
be first boiled in a solution of common washing soda, and then the oxide
removed by passing it rapidly in and out of some "Dipping Acid," which is
prepared by mixing together equal parts of oil of vitriol and nitric acid; when
removed from the "Dipping Acid," it must be well washed in water, and may
remain under the surface of the water until the silvering solution is ready. A
silver solution may be prepared by dissolving a sixpence in some nitric acid
contained in a flask; it is then poured into a solution of common salt, which
precipitates the chloride of silver, and leaves the copper in solution—the latter is
poured off when the chloride has subsided, and after being well washed in some
boiling water, is dissolved in a solution of cyanide of potassium. If a clean
electrotype is plunged into this solution, it is immediately covered with a very
thin coating of silver, which of course would soon wear off, and in order to
increase the thickness of the silver deposit, a single cell arrangement may be
constructed of a large gallipot containing a wide porous cell and a circle of

amalgamated zinc around it; the arrangement is set in action by pouring a
solution of salt (or, still better, sal ammoniac) into and around the porous vessel,
and the silvering solution into the latter; a connecting wire passes from the zinc,
and the article being attached to it, is now plunged into the porous cell, when a
current of electricity slowly passes and deposits the silver on the copper article.
(Fig. 189.)

Fig. 189.
The gallipot containing the solution of sal ammoniac, with the circular amalgamated zinc
with wire and binding screw to which the medal is attached, and contained in the porous
vessel holding the silvering solution and medal.

Twelfth Experiment.

Separate batteries and large troughs containing a solution of cyanide of silver in
cyanide of potassium are used on a grand scale in the electro-plating
establishment of Messrs. Elkington of Birmingham, where the finest specimens
of the art are to be obtained; a plate of silver being attached to the anode to
supply the loss of silver in these troughs.

Thirteenth Experiment.

The art of gilding by the agency of electricity is quite as simple as the processes
already described, although greater care is necessary to avoid any loss of the
precious metal. A small bit of gold is dissolved in a mixture of three parts

muriatic acid and one of nitric acid, which forms the chloride of gold. This is
then digested with an excess of calcined magnesia, and the gold is precipitated
as an oxide of the metal; the latter is collected and washed, and then boiled in
strong nitric acid to remove the magnesia clinging to it, and being again
thoroughly washed with water, is dissolved in a solution of cyanide of
potassium, forming a solution of cyanide of gold and potassium, which may be
placed in the porous cell of the single cell arrangement already described in the
Eleventh Experiment.

Fourteenth Experiment.

The safest and surest mode of making a gilding solution is to dissolve some
cyanide of potassium in water in a gallipot, and having placed a porous vessel
therein containing the same solution, put a plate of copper into the porous cell,
and some thin foil of pure gold into the gallipot; connect the gold with the anode
of a single cell of Daniell, and the copper in the porous cell with the cathode,
and in a few hours sufficient gold will be dissolved for the purpose of gilding.
It is usually recommended to warm the gilding solution till it reaches a
temperature of about 150° Fahr., and a very moderate battery power is employed
in Electro Gilding. Indeed the same arrangement, shown in the Eleventh
Experiment, (Fig. 189.) Page 202, will also answer for the gilding solution. After
being gilt, the articles may be rubbed with a little tripoli, or burnished (with
taste) by the handle of a key.

Fifteenth Experiment.

Passing on to the more brilliant results obtainable from a powerful voltaic
battery (of at least thirty pairs of Grove), the beautiful incandescence of
platinum wire may first be noticed. If a wire of this metal is stretched between
the brass standards of two ring stands, the length must be proportioned to the
power of the battery; the adjustment can be made very conveniently by twisting
the platinum wire on one ring stand, and then leaving the other end loose, the
second ring stand may be brought nearer and nearer to the first, until the desired
intensity of light from the incandescent wire is obtained. (Fig. 190.) If the wire is
contained in a glass tube the cooling effect of currents of air is prevented, and a
much greater length of wire can be made hot.

Fig. 190.
a a. Two ring stands with the battery wires b b (which should be a convenient length)
attached. c. Platinum wire, fixed end. d. The other end held in one hand and shortened as
the stand is moved by the other hand.

Sixteenth Experiment.

With the same arrangement, a chain composed of alternate links of silver and
platinum wire presents a very pretty effect, every alternate link of platinum
being incandescent, whilst the silver, from its excellent conducting power,
remains comparatively cool.

Seventeenth Experiment.

Fireworks or gunpowder, arranged in proper cases, are fired at a great distance
from the voltaic battery by heating a thin iron or platinum wire contained within
them by the passage of the electricity; and submarine and other explosions of
gunpowder by the same agency have become a common engineering operation.
(Fig. 191.)

Fig. 191.
a. A Gerb firework with two holes punctured, through which the bit of iron wire passes,
and is wound round the battery wires tied to the outside of the case. c. A gut bladder
containing the thin wire and powder for a miniature submarine explosion.

During the operation of blasting the hard marl rocks in the River Severn by Mr.
Edwards, C.E., a number of holes were made side by side in the bed of the river,
and cartridges formed of strong duck or canvas, tapered at the bottom, were
filled with charges of powder from two to four pounds, according to the depth of
the marl; thus, two pounds for four feet, three pounds for four feet six inches,
and four pounds for five feet. Into the bag were conveyed the wires of the voltaic
battery, or Bickford's fuse, and being then coated with pitch and tallow, and
finally greased all over and dusted with whitening, they rarely failed, and were
all fired simultaneously under water. The pitch and tallow first, and afterwards
the simple tallow, effectually excluded the water from the gunpowder contained
in the canvas bag.

Eighteenth Experiment.

The burning of various metals by the battery is displayed with great effect by De
la Rue's discharger, as also the incandescence of the charcoal points producing
the electric light. The illuminating power derived from a forty-cell Grove's
battery of the ordinary size is about equal to the light of 500 candles.

Fig. 192.
De la Rue discharger, containing a series of six pairs of different substances, such as
charcoal, iron, lead, zinc, copper, antimony, in six pair of crayon holders, and turning on a
centre, so as to be changed at pleasure.

Fizeau and Foucault have made a careful comparison of the light obtained from
92 carbon couples as arranged in a Bunsen's battery, and of the oxy-hydrogen, or
Drummond Light, as compared with that of the sun, and they state that "On a
clear August day, with the sun two hours high, the electric light (assuming the
sun as unity) bore to it the ratio of one to two and a half—i.e., the sun was two
and a half times more powerful, while the Drummond Light was only 1/146th
that of the sun." Bunsen found the light from 48 carbons equal to 572 candles. In
Bunsen's battery carbon is substituted for the platinum in Grove's arrangement;
and simultaneously with Bunsen, Cooper (in England) had applied charcoal for
the same purpose.
At night the giant ship (Polyphemus like) is to have an electric light at the mast-
head whilst steaming across the Atlantic.

Fig. 193.
Great Eastern, with electric light.

CHAPTER XV.
MAGNETISM AND ELECTRO-MAGNETISM.

If a small helix, or coil of covered wire, is arranged with an unmagnetized steel
needle within it, so that the discharge of a large Leyden jar may take place
through the coil, the needle will be found strongly magnetic after the discharge
of the electricity. (Fig. 194.) Many years before this was known, it had been
noticed that when a ship was struck by lightning, the compasses were generally
reversed; and in a special case, where a house was struck, the electricity entered
a box of knives, fusing some, tearing the handles off others, but leaving them
strongly magnetic. Electricians tried to repeat the effect by sending the discharge
of powerful Leyden batteries through bars of steel without any important result;
and it was not until Oersted, in the year 1819, made his important discovery that
the copper wire conveying the electricity possessed peculiar magnetic power,
that the principle began to be understood, and then the electricians succeeded in
imitating the effects of lightning on steel, as already described in the beginning
of this chapter. (Fig. 194.)

Fig. 194.
a a. A glass tube supported on two uprights of wood, with coil of copper wire passing
round it, terminating in the balls b b. c. Needle to place inside glass tube.

When the electricity has passed away from the Leyden jar through the coil of
copper wire, it no longer possesses any power to affect a piece of steel or iron,
but if the wires of the voltaic battery are now connected with the coil of copper
wire, which should be covered with cotton or silk, and many yards in length,
then a bar of steel or soft iron is not only rendered magnetic, but remains
permanently so, as long as the current of electricity continues to pass along the
coil of wire, so that if some nails or iron filings are brought to the bar of iron,
one end of which projects from the coil, they cling to it with great force, and a
great number of nails may be hung on in this manner, but they immediately fall
off when the contact is broken with the battery. (Fig. 195.)

Fig. 195.
Electricity thus becomes a source of magnetism, and the discoverer, Oersted,
found that only needles or bars of steel or iron were thus affected, and not those
of brass, shell-lac, sulphur, and other substances; he termed the conducting wire
"a conjunctive wire," and described the effect of the electric current or "electric
conflict," as he called it, as resembling a Helix (from ἑλισσω, to turn round; a
screw or spiral), and that it is not confined to the conducting wire, but radiates
an influence at some distance. This latter statement is exactly in accordance with
our present notions, and hence the coil conveying the current is said to induce
magnetism in the iron or steel, just as the phenomena of induction are produced
with frictional electricity. The effect of Oersted's discovery, says Silliman, was
truly electric; the scientific world was ripe for it, and the truth he thus struck out
was instantly seized upon by Arago, Ampère, Davy, Faraday, and a crowd of
philosophers in all countries. The activity with which this new field of research
has been cultivated, has never relaxed even to this hour, while it has borne fruit

in a multitude of theoretical and practical truths, and above all, in the electro-
magnetic telegraph, truly called, and especially in connexion with the Atlantic
telegraph wire, "the great international nerve of sensation."
Magnetism is not only the result of a current of electricity through any good
conductor, but there are certain oxides of iron, called magnetic iron ores, which
have the property of attracting iron filings, and are mostly found in primitive
rocks, being abundant at Roslagen, in Sweden, and called the loadstone, from its
always pointing, when freely suspended, to the Polar, North, or Load Star. If a
tolerably large specimen of this mineral is examined, there will be found usually
two points where the iron filings are attracted in larger quantities than in other
parts of the same specimen. These attractive points are called poles, and the
loadstone being properly mounted with soft iron bars, termed cheeks, bound
round it (in old-fashioned loadstones) with silver plate and duly ornamented
with engraving, has its magnetic power greatly increased, and is then said to be
endowed with magnetic polarity; and to prevent the loss of power, a soft piece of
iron, called the armature, is placed across and attracted to the poles of the
loadstone. (Fig. 196.)

Fig. 196.
A loadstone mounted in brass or silver, with the iron cheeks b b attached. c. The bit of soft
iron called the armature.

Second Experiment.

If a needle of tempered steel (fitted with a little brass cup in the centre to work
upon a point) is rubbed with the loadstone in one direction only, it is rendered
permanently magnetic, and will now be found to take a certain fixed position,
pointing always in a direction due north and south. The end which points
towards the north is called the north pole, and the other extremity the south pole,
and it is usual to mark the north pole with an indent or scratch to distinguish it at
all times.

Third Experiment.

If another bar of steel is magnetized, and the north pole duly marked, and then
brought towards the same pole of the suspended magnet, instant repulsion takes
place; the magnet, of course, grasped in the hand is not free to move, but the
small magnet immediately shows the same fact noticed with electricity, viz.,
"that similar magnetisms repel." Two north poles repel each other, but when the
bar of steel is reversed, the opposite effect occurs, and the suspended magnet is
attracted, showing that dissimilar magnetisms attract, and a north will attract a
south pole. (Fig. 197.)

Fig. 197.
A magnetic needle, the north pole n being attracted to the south pole of the bar magnet s,
and repelled from the north end.

Fourth Experiment.

By contact, the magnetic power is transferred from the magnet to a piece of
unmagnetized steel, and it is stated that the highest magnetizing effect is that
produced by the simple method of Jacobi. A horse-shoe magnet has its poles

brought in contact with the intended poles of another bar of steel, likewise bent
in the form of a horse-shoe, and by drawing the feeder over the unmagnetized
horse-shoe in the direction of the arrow in the cut, and when it reaches the curve,
bringing it back again to the same place, say at least twelve times, and after
turning the whole over without separating the poles, and repeating the same
operation on the other side likewise twelve times, the steel is then powerfully
magnetized; and it is said that a horse-shoe of one pound weight may be thus
charged so as to sustain twenty-six and a half pounds, and that by the old method
of magnetizing it would only have sustained about twenty-two pounds. (Fig.
198.)

Fig. 198.
The horse-shoe magnet, and another one unmagnetized, placed end to end; the one shaded
and lettered n and s is the magnet. a a. The piece of soft iron moved in the direction of the
arrow.

Fifth Experiment.

If the horse-shoe magnet is placed on a sheet of paper, and some iron filings are
dusted between the poles, a very beautiful series of curves are formed, called the
magnetic curves, which indicate the constant passage of the magnetic power
from pole to pole.

Sixth Experiment.

The magnetic force exerted by a horse-shoe-shaped piece of soft iron,
surrounded with many strands of covered copper wire in short lengths, is
extremely powerful (Fig. 199), and enormous weights have been supported by
an electro-magnet when connected with a voltaic battery. Supposing a man were

dressed in complete armour, he might be held by an electro-magnet, without the
power of disengaging himself, thus realizing the fairy story of the bold knight
who was caught by a rock of loadstone, and, in full armour, detained by the
unfriendly magician.

Fig. 199.
a. Powerful electro-magnet supporting a great weight. b. The battery.

Seventh Experiment.

When a piece of soft iron is held sufficiently near one of the poles of a powerful
magnet, it becomes by induction endowed with magnetic poles, and will support
another bit of soft iron, such as a nail, brought in contact with it. When the
magnet is removed, the inductive action ceases, and the soft iron loses its
magnetic power. This experiment affords another example of the connexion
between the phenomena of electricity and magnetism. It is in consequence of the
inductive action of the magnetism of the earth that all masses of iron, especially
when they are perpendicular, are found to be endowed with magnetic polarity;
hence the reaction of the iron in ships upon the compasses, which have to be
corrected and adjusted before a voyage, or else serious errors in steering the
vessel would occur, and there is no doubt that many shipwrecks are due to this

cause. No other metals beside iron, steel, nickel, cobalt, and possibly
manganese, can receive or retain magnetism after contact with a magnet.
The remarkable effect of magnetism upon all matter, so ably investigated by
Faraday and others, will be explained in another part of this book—viz., in the
article on Dia-Magnetism.

Fig. 200.
Magician and his loadstone-rock.—Vide Fairy Tale.

CHAPTER XVI.
ELECTRO-MAGNETIC MACHINES.

The experiments already described in illustration of some of the phenomena of
electro-magnetism are of such a simple nature that they may be comprehended
without difficulty; but it is not such an easy task to appreciate the curious fact of
an invisible power producing motion. It has already been explained that a copper
or other metallic wire conveying a current of electricity becomes for the time
endowed with a magnetic power, and if held above, or below, or close to, a
suspended magnetized steel needle, affects it in a very marked degree, causing it
to move to the right or left, according to the direction of the electric current; and
in order to form some notion of the condition of a metallic wire whilst the
electricity is passing through it, the annexed diagrams may be referred to. (Figs.
201, 202.)

Fig. 201.
Portion of a square copper conductor, in which a b represents the direction of the
electricity, and the small arrows, c c c c, the magnetic current or whirl at right angles to the
electrical current, and exercising a tangential action.

Fig. 202.
A round conducting wire, in which the electrical current is flowing in the direction of the
large dart a b, and the small arrows indicate the direction of the magnetic force.

Dr. Roget says: "The magnetic force which emanates from the electrical
conducting wire is entirely different in its mode of operation from all other
forces in nature with which we are acquainted. It does not act in a direction
parallel to that of the current which is passing along the wire, nor in any plane
passing through that direction. It is evidently exerted in a plane perpendicular to
the wire, but still it has no tendency to move the poles of the magnet in a right or
radial line, either directly towards, or directly from, the wire, as in every other
case of attractive or repulsive agency. The peculiarity of its action is that it
produces motion in a circular direction all round the wire—that is, in a direction
at right angles to the radius, or in the direction of the tangent to a circle
described round the wire in a plane perpendicular to it; hence the electro-
magnetic force exerts a tangential action, or that which Dr. Wollaston called a
vertiginous or whirling motion.
Dr. Faraday concluded that there is no real attraction or repulsion between the
wire and either pole of a magnet, the action which imitates these effects being of
a compound nature; and he also inferred that the wire ought to revolve round a
magnetic pole of a bar magnet, and a magnetic pole round a wire, if proper
means could be devised for giving effect to these tendencies, and for isolating
the operations of a single pole. For the first idea of electro-magnetic rotation the
world is indebted to Dr. Wollaston; but Dr. Faraday, with his usual ingenuity,
was the first who carried out the theory practically. The rotation of a wire
(conveying a current of voltaic electricity) round one of the poles of a magnet is
well displayed with the simple contrivance devised by him. (Fig. 203.)

Fig. 203.
n. A small bar magnet cemented into a wine-glass, the north pole being at n. a is a
moveable wire looped over the hook, which is the positive (+) pole of the battery; the free
extremity rotates round the pole of the magnet when the current of electricity passes. The
dotted line represents the level of the mercury which the glass contains. The electricity
passes in at a, and out at the wire b, as shown by the arrows. c is connected with the
negative, and d with the positive, pole of the battery.

By a careful observation of the complex action of an electrified wire upon a
magnetic needle, Dr. Faraday was enabled to analyse the phenomena with his
usual penetration and exhaustive ability, and he found, as Daniell relates,—

"That if the electrified wire is placed in a perpendicular position, and made
to approach towards one pole of the needle, the pole will not be simply
attracted or repelled, but will make an effort to pass off on one side in a
direction dependent upon the attractive or repulsive power of the pole; but
if the wire be continually made to approach the centre of motion by either
the one or the other side of the needle, the tendency to move in the former
direction will first diminish, then become null, and ultimately the motion
will be reversed, and the needle will principally endeavour to pass in the
opposite direction. The opposite extremity of the needle will present similar
phenomena in the opposite direction; hence Dr. Faraday drew the
conclusion that the direction of the forces was tangential to the
circumference of the wire, that the pole of the needle is drawn by one force,

not in the direction of a radius to its centre, but in that of a line touching its
circumference, and that it is repelled by the other force in the opposite
direction. In this manner the northern force acted all round the wire in one
direction, and the southern in the opposite one. Each pole of the needle, in
short, appeared to have a tendency to revolve round the wire in a direction
opposite to the other, and, consequently, the wire round the poles. Each
pole has the power of acting upon the wire by itself, and not as connected
with the opposite pole, and the apparent attractions and repulsions are
merely exhibitions of the revolving motions in different parts of their
circles."

The same fact illustrated at Fig. 203, is also demonstrated in a still more striking
manner by means of wire bent into a rectangular form, and so arranged that
whilst the current of electricity passes, it is free to move in a circle; and when
the poles of a magnet are brought towards the electrified wire, it may be
attracted or repelled at pleasure, and in fact becomes a magnetic indicator, and
places itself (if carefully suspended) at right angles to the magnetic meridian.
(Fig. 204.)

Fig. 204.
a a a a. The rectangular wire covered with silk and varnished, one end of which being
pointed, rests on the little cup b, connected with a covered wire passing down the centre of
the brass support to the binding screw c let into ivory. d. The other extremity of the
rectangular wire; this being covered and varnished, is not in metallic contact with the end b,
but is likewise pointed, and dips into the mercury contained in the large cup e e. The upper

and lower cups do not touch, and are separated by ivory, marked by the shaded portion, and
the cup e e is in metallic communication with the brass pillar, and is connected with the
negative pole of the battery at f, whilst c is connected with the positive pole of the battery,
and the electricity circulates round the wire in the direction of the arrows. When a bar
magnet, n, is brought towards the wire, the latter is immediately set in motion, and by
alternately presenting the opposite poles of the magnet, the rectangular wire rotates freely
round the cup b.

These curious movements of a magnetized needle, and rotations of wires and
magnets, brought about by the agency of an active current of electricity, have
induced Sir David Brewster to advance his admirable theory, which supposes the
affection of the mariner's compass needle, and all other suspended pieces of
steel, to be due to the agency of electrical currents continually circulating
around the globe; and Mr. Barlow contrived the following experiment in
illustration of Brewster's theory. A wooden globe, sixteen inches in diameter,
was made hollow, for the purpose of reducing its weight, and while still in the
lathe, grooves one-eighth of an inch deep and broad were cut to represent an
equator, and parallels of latitude at every four and a half degrees each way from
the equator to the poles. A groove of double depth was also cut like a meridian
from pole to pole, but only half round. The grooves were cut to receive the
copper wire covered with silk, and the laying on was commenced by taking the
middle of a length of ninety feet of wire one-sixteenth of an inch in diameter,
which was applied to the equatorial groove so as to meet in the transverse
meridian; it was then made to pass round this parallel, returned again along the
meridian to the next parallel, and then passed round this again, and so on, till the
wire was thus led in continuation from pole to pole. The length of wire still
remaining at each pole was returned from each pole along the meridian groove
to the equator, and at this point, each wire being fastened down with small
staples, the wires from the remaining five feet were bound together near their
common extremity, when they opened to form separate connexions for the poles
of a voltaic battery. When the battery was connected, and magnetic needles
placed in different positions, they behaved precisely as they would do on the
surface of the earth, the induction set up by the electrified wire being a perfect
imitation of that which exists on the globe.
The opposite effect to that already described—viz., the rotation of one pole of a
magnet round the electrified wire, was also arranged by Faraday in the following
manner. (Fig. 205.)

Fig. 205.
n s. A little magnet floating in mercury contained in the glass a a; the north pole is allowed
to float above the surface of the quicksilver, and the south pole is attached to the wire
passing through the bottom of the glass vessel. The electricity passes in at b, and taking the
course indicated by the arrows travels through the glass of quicksilver to the other pole of
the battery at c. Directly contact is made with the battery, the little magnet rotates round the
electrified wire, w. The dotted line shows the level of the mercury in glass.

In the examination of the magnetic phenomena obtained from wires transmitting
a current of electricity, it should be borne in mind that any conducting medium
which forms part of a closed circuit—i.e., any conductor, such as charcoal,
saline fluids, acidulated water, which form a link in the endless chain required
for the path of the electricity,—will cause a magnetic needle placed near it to
deviate from its natural position.
These positions of the electrified wire and the magnetic needle are of course
almost unlimited, and in order to assist the memory with respect to the fixed
laws that govern these relative movements, Monsieur Ampère has suggested a
most useful mechanical aid, and he says:—"Let the observer regard himself as
the conductor, and suppose a positive electric current to pass from his head
towards his feet, in a direction parallel to a magnet; then its north pole in front of
him will move to his right side, and its south pole to his left.

"The plane in which the magnet moves is always parallel to the plane in
which the observer supposes himself to be placed. If the plane of his chest

is horizontal, the plane of the magnet's motion will be horizontal, but if he
lie on either side of the horizontally-suspended magnet, his face being
towards it, the plane of his chest will be vertical, and the magnet will tend
to move in a vertical plane."

This very lucid comparison will be seen to apply perfectly to the direction of the
rotations in Figs. 203 and 205.
The whole of this apparatus is made in the most elegant and finished manner by
Messrs. Elliott, of 30, Strand; and by a modification of the latter arrangement
(Fig. 206), the opposite rotations of the opposite poles of the magnets round the
electrified wire, are shown in the most instructive manner. The apparatus (Fig.
206) was devised by the late Mr. Francis Watkins, and consists of two flat bar
magnets doubly bent in the middle, and having agate cups fixed at the under part
of the bend (by which they are supported) upon upright pointed wires, the latter
being fixed upright on the wooden base of the apparatus, and the magnets turn
round them as upon an axis.

Fig. 206.
a. Wire conveying the current of electricity. b b. The magnets balanced on points rotating
round the wires.

Two circular boxwood cisterns, to contain quicksilver, are supported upon the
stage or shelf above the base. A bent pointed wire is directed into the cup of each

magnet, the ends of which dip into the mercury contained in the boxwood
circular troughs on the stage. By using a battery to each magnet, and taking care
that the currents of electricity flow precisely alike, they will then rotate in
opposite directions.
Directly after the ingenious experiments of Faraday became known, a great
number of electro-magnetic engine models were constructed, and many thought
that the time was fast approaching when steam would be superseded by
electricity; and really, to see the pretty electro-magnetic models work with such
amazing rapidity, it might be supposed that if they were constructed on a larger
scale, a great amount of hard work could be obtained from them. This idea,
however, has been proved to be a fallacy, for reasons that will be presently
explained. The figure on p. 216 displays two of these engines, one of which
represents the rotation of electro-magnets within four fixed steel magnets, and
the other the rotation of steel magnets by the fixed electro-magnets. The latter
(No. 2) moves with such great velocity, that unless the strength of the battery is
carefully adjusted, the connexions are soon destroyed. (Fig. 207.)

Fig. 207.
No. 1 consists of vertical permanent steel magnets and horizontal soft-iron electro-magnets
which rotate.
No. 2 consists of two fixed soft-iron electro-magnets, and four bent permanent steel
magnets, which rotate, in both cases of course, only when connected with the battery.

Considering the prodigious power or pull of a soft-iron electro-magnet, and its
capability of supporting considerable weight, the most reasonable expectations
of success might be entertained with machines acting by the direct pull. It was,

however, discovered that they soon became inefficient, from the circumstance
that the repeated blows received by the iron so altered its character, that it
eventually assumed the quality of steel, and had a tendency to retain a certain
amount of permanent magnetism, and thus to interfere with the principle of
making and unmaking a magnet. It was this fact that induced Professor Jacobi,
of St. Petersburg, after a large expenditure of money, to abandon arrangements
of this kind, and to employ such as would at once produce a rotatory motion.
The engine thus arranged was tried upon a tolerably large scale on the Neva, and
by it a boat containing ten or twelve people was propelled at the rate of three
miles an hour.
Various engines have been constructed by Watkins, Botta, Jacobi, Armstrong,
Page, Hjorth; the engine made by the latter (Hjorth) excited much attention in
1851-52, and consisted of an electro-magnetic piston drawn within or repelled
from an electro-magnetic cylinder; and by this motion it was thought that a
much greater length of stroke could be secured than by the revolving wheels or
discs, but the loss of power (not only in this engine, but in others) through space
is very great, and the lifting power of any magnet is greatly reduced and altered
at the smallest possible distance from its poles. This loss of power is therefore a
great obstacle in the way of the useful application of electro-magnetic force, and
can be appreciated even with the little models, all of which may be stopped with
the slightest friction, although they may be moving at the time with great
velocity.
In the second place, supposing the reduced force exerted by the two magnets, a
few lines apart, was considered available for driving machinery, the moment the
magnets begin to move in front of one another there is again a great loss of
power, and as the speed increases, there is curiously a corresponding diminution
of available mechanical power, a falling-off in the duty of the engine as the
rotations become more rapid. In the third place, the cost of the voltaic battery, as
compared with the consumption of coal in the steam-engine, is very startling,
and extremely unfavourable to electro-magnetic engines.
Mr. J. P. Joule found that the economical duty of an electro-magnetic engine at a
given velocity and for a given resistance of the battery is proportioned to the
mean intensity of the several pairs of the battery. With his apparatus, every
pound of zinc consumed in a Grove's battery produced a mechanical force
(friction included) equal to raise a weight of 331,400 pounds to the height of one
foot, when the revolving magnets were moving at the velocity of eight feet per
second. Now, the duty of the best Cornish steam-engine is about one million five

hundred thousand pounds raised to the height of one foot by the combustion of
each pound of coal, or nearly five times the extreme duty that could be obtained
from an electro-magnetic engine by the consumption of one pound of zinc. This
comparison is therefore so very unfavourable, that the idea of a successful
application of electricity as an economic source of power, is almost, if not
entirely abandoned.
By instituting a comparison between the different means of producing power, it
has been shown that for every shilling expended there might be raised by

Pounds.
Manual power 600,000one foot high in a day.
Horse 3,600,000 " "
Steam 56,000,000 " "
Electro-magnetism 900,000 " "

A powerful magnet has been compared to a steam-engine with an enormous
piston but with an exceedingly short stroke. Although motive power cannot be
produced from electricity and applied successfully to commercial purposes, like
the steam-engine, yet the achievements of the electric telegraph as an application
of a small motive power must not be lost sight of, whilst the fall of the ball at
Deal and other places, by which the chronometers of the mercantile navy are
regulated, as also the means of regulating the time at the General Post Office and
various railway stations, are all useful applications of the power which fails to
compete in other ways with steam.

CHAPTER XVII.
THE ELECTRIC TELEGRAPH.

The engineering and philosophical details of this important instrument have
grown to such formidable dimensions, that any attempt (short of devoting the
whole of these pages to the subject) to give a full account of the history and
application of the instrument, the failures and successes of novel inventions, and
the continued onward progress of this mode of communication, must be
regarded as simply impossible, and therefore a very brief account of the
principle only will be attempted in these pages.
For the complete history of the discovery and introduction of the principle of the
Electric Telegraph the reader is referred to the Society of Arts Journal (Nos. 348-
9, vol. viii.), where it is stated that it is half a century, dating from August, 1859,
since the first galvanic telegraph was made. "It was the Russian Baron
Schilling's electro-magnetic telegraph which, without its being known to be his,
was brought to London, and caused the establishment of the first practically
useful telegraph lines, not only in Great Britain, but in the world." Dr. Hamel
says: "The small sprout nursed on the Neva, which had been exhibited on the
Rhine, and thence brought to the Thames, grew up here to a mighty tree, the
fruit-laden branches of which, along with those from trees grown up since,
extend more and more over the lands and seas of the Eastern hemisphere, whilst
kindred trees planted in the Western hemisphere have covered that part of the
world with their branches, some of which will, ere long, be interwoven with
those in our hemisphere."
The first telegraph line in England was constructed by Mr. Cooke from
Paddington along the Great Western Railroad to West Drayton in 1838-39; and it
must be remembered that it was in February, 1837, that Mr. Cooke first
consulted Professor Charles Wheatstone, having previously visited Dr. Faraday
and Dr. Roget, and on the 19th November, 1837, a partnership contract was
concluded between Messrs. Cooke and Wheatstone.
To the distinguished philosopher, Professor Wheatstone, the merit of the
ingenious construction of the vertical-needle telegraph is due; whilst Mr.
Cooke's name will always be associated with the practical establishment of the
first telegraph lines in England. The first line in the United States, from

Washington to Baltimore, was completed in 1844, being arranged and worked
by Professor Morse.
In British India, in April and May, 1839, the first long line of telegraph, twenty-
one miles in length, and embracing 7000 feet of river surface, was constructed
by Dr. (now Sir William) O'Shaughnessy.
The construction of the electric telegraph may be considered under three heads:
1st. The Battery, the motive power.
2nd. The Wires, the carriers of the force.
3rd. The Instruments to be worked—the bell and the needle telegraph.

THE BATTERY.

The construction and rationale of the batteries generally in use have been
explained in another part of this work; those used for telegraphic purposes
consist of one or more couples, of which zinc is one, the second being copper,
silver, platinum, or carbon. Each couple is termed an element, and a series of
such couples a battery.
The batteries employed chiefly on the English lines consist of a plate of cast-
zinc four inches square and 3/16ths of an inch thick, attached by a copper strap
one inch broad to a thin copper plate four inches square. The zinc is well
amalgamated with mercury. Twelve of these couples are arranged in a trough of
wood, porcelain, or gutta-percha, divided by partitions into twelve water-tight
cells, 1¼ inch wide. The zinc and copper preserve the same order and direction
throughout, and when arranged, the trough is filled with the finest white sand,
and then moistened with water previously mixed with five per cent. by measure
of pure sulphuric acid. This mode of applying the acid is the clever practical
improvement of Mr. Cooke, and prevents any inconvenience from the spilling of
the acid, and at the same time renders the battery quite portable. The voltaic
arrangement thus prepared is found to remain in action for several weeks, or
even months, with the occasional addition of small quantities of acid, and
answers well for working needle telegraphs in fine and dry weather. In fogs and
rains, at distances exceeding 200 miles at most, their action is not so perfect, and
a vast number of couples must be employed, 144 to 288 being frequently in use.
In France, Prussia, and America, sand batteries do not appear to answer, and
Daniell's arrangement is preferred. Sixty couples suffice in France for some of

the long lines—viz., from Paris to Bordeaux, 284 miles; Paris to Brussels, 231¼
miles; and in fact, the advantages of the Daniell's battery have become so
apparent, that they are now being used on English lines. In Prussia, Bunsen's
carbon battery is much used; in India, a modification of Grove's battery is
preferred, the zinc being acted upon by a solution of common salt in water. Two
of these elements were found sufficient to work a line of forty miles totally
uninsulated, and including the sub-aqueous crossing of the Hooghly River, 6200
feet wide.
The continual energy of the battery, whatever may be its construction, depends
on the circulation of the electricity, the object being to pass the force from the
positive end of the series through the wires, back again to the negative extremity
of the voltaic series.
The wire (the carrier of the force) must be continuous throughout, unless, of
course, water or earth forms a part of the endless conducting chain.

THE CONDUCTING WIRES.

These roads for the electricity may be of any convenient metal, and the one
preferred and used is iron, which is well calculated from its great tenacity (being
the most tenacious metal known) and cheapness to convey the electricity,
although it is not such a good conductor as copper, and offers about six times
more resistance to the flow of the current than the latter metal. The wire does not
appear to be made of iron, because it is galvanized or passed through melted
zinc, which coats the surface and defends it from destructive rust, at the same
time does not destroy its valuable property of tenacity or power of resisting a
strain. About one ton of wire is required for every five miles, and to support this
weight, stout posts of fir or larch are erected about fifty yards apart, and from ten
to twenty-five feet high. At every quarter mile, on many lines, are straining-posts
with ratchet wheel winders, for tightening the wires. On some of the lines the
wires are attached to the posts by side brackets carrying the insulators invented
by Mr. C. V. Walker, which are composed of brown salt-glazed stoneware of the
hour-glass shape, as shown in the drawing. (Fig. 208.)

Fig. 208.
Walker's insulator.

There are some objections to the hour-glass insulators, and they have been
modified by Mr. Edwin Clark, who employs a very strong stone-ware hook open
at the side, so that the wire can be placed on the hook without threading, and the
hooks can be replaced in case of breaking, without cutting the telegraph wire,
which is securely fastened to each insulator by turns of thinner wire. An inverted
cap of zinc is used to keep the insulator dry. (Fig. 209.)

Fig. 209.

Clark's insulator.

In India the conductor is rather a rod than a wire, and weighs about half a ton per
mile; it is erected in the most substantial manner, and many miles of the rod are
supported on granite columns, other portions on posts of the iron-wood of
Arracan, or of teak.
The number of wires required by the electric telegraph often puzzles the railway
traveller, and people ask why so many wires are used on some lines and so few
on others? The answer is very simple: they are for convenience. Two wires only
are required for the double needle telegraph, and one for the single needle
instrument. But as so many instruments are required at the terminal stations, an
increased number of wires, like rails for locomotives, must be provided; thus, on
the Eastern Counties, seven wires are visible, and are thus employed. The two
upper wires pass direct from London to Norwich; the next pair connect London,
Broxbourne, Cambridge, Brandon, Chesterfield, Ely; the third pair all the small
stations between London and Brandon; and the seventh wire is entirely devoted
to the bell.
If the earth was not a conductor of electricity, and employed in the telegraphic
circuit, four wires would be required for the double needle telegraph, and two
for the single instrument. To understand this, let us suppose a battery circuit
extending from Paddington to the instrument at Slough, and the wire returning
from Slough to Paddington, it is evident that one wire would take the electricity
to Slough, and the other return it to London, as in the diagram below. (Fig. 210.)

Fig. 210.
a. The battery. b. The instrument. The arrows show the passage of the electricity to the
single needle telegraph instrument by one wire, and the return current by the other.

If the whole of the return wire is cut away except a few feet at each end, which
are connected by plates of copper with the damp earth, the current not only
passes as before, but actually has increased in intensity, and will cause a much
more energetic movement of the needle in the telegraph instrument. (Fig. 211.)

These plates are called "Earth Plates;" and Steinheil, in 1837, was the first who
proved that the earth might perform the function of a wire.

Fig. 211.
a. The battery. b. The instrument. c. Earth plate at Slough. d. Earth plate at London. The
arrows show the direction of the electric current.

It must be obvious that a message may be received at any station without a
battery, but in order to be able to return an answer, every station must have its
own battery.
Ingeniously-constructed lightning-conductors are attached to the posts which
carry the wires, so that in case of a storm, the natural electricity is conveyed to
the earth, whilst the voltaic electricity artificially produced pursues its own
course without deviation. Protectors are also required for the instruments at the
stations, and the plan devised by Mr. Highton is thus described by the inventor:
—
"A portion of the wire circuit—say for six or eight inches—is enveloped in
blotting-paper or silk, and a mass of metallic filings, in connexion with the earth,
is made to surround it. This arrangement is placed on each side of the telegraph
instrument at a station. When a flash of lightning happens to be intercepted by
the wires of the telegraph, the myriads of infinitesimally fine points of metal in
the filings surrounding the wire at the station, on having connexion with the
earth, at once draw off nearly the whole charge of lightning, and carry it safely
to the earth."

THE INSTRUMENTS TO BE WORKED—THE BELL AND THE
TELEGRAPH.

The bell or alarum resembles in construction that of an ordinary clock, and is in
fact a piece of clockwork wound up and ready to ring a bell, when the detent or
preventive is removed. The detent is connected with a piece of soft iron placed
before an electro-magnet, and directly the current passes, the electro-magnet
attracts the soft piece of iron attached to a perpendicular lever which the bell-
crank lever rests upon; the detent is removed, and the bell rings, and again stops
when the current of electricity ceases to pass.
One of the most simple alarum clocks is a common American clock, wound up
daily. A small electro-magnet surrounded with thick wire is placed below a
moveable piece of tinned iron, so that when this is attracted, the fly of the clock
is released, and its bell tolls unceasingly while the magnet is excited. This
arrangement is employed by Sir W. O'Shaughnessy in the Indian telegraph
system. (Fig. 212.)

Fig. 212.
a. The soft iron tinned, which is attracted to the electro-magnet b, and liberates the detent.

It will readily be comprehended from this description that the alarum is sounded
by ordinary mechanism, and that the duty of the current of the electricity is
simply comprised in the act of removing the lever and liberating machinery,
which may be large or small; and if it were thought necessary, the bells of the
great clock-tower of the Houses of Parliament, which chime the quarters, or
even "Big Ben" himself (when his constitution is restored), could be rung by a
person at York or Edinburgh, supposing wires, batteries, and a powerful electro-

magnet with a detent mechanism for the bells, were properly arranged and
connected with the clockwork.
In certain cases, Mr. Charles V. Walker states that a single and distinct wire is
used for the bell only, with his special mechanism, called the ringing key. If the
bell was always on the same wire as the needle-coil, the bell would not only call
the attention of, but seriously annoy the clerk (unless, of course, he happened to
be a very deaf person) by its ringing whilst he was reading the signals of the
needle. The nuisance is prevented by what is termed joining over or making the
short circuit—in fact, by providing for the current a shorter and much more
capacious road to the needle coil than by going through that of the bell-magnet,
which is made with very fine wire; and the control of the short circuit is put in
the hands of the clerk.

COOKE AND WHEATSTONE'S DOUBLE NEEDLE TELEGRAPH.

The principle of this instrument, as already explained, is involved in the
elementary experiment of Oersted—viz., the deflection of a magnetic needle
from the inside of a coil of wire conveying a current of electricity, and as it is
difficult to give a good description and drawing of the interior of the instrument
that can really be understood, it may be sufficient to state that the handles give
the operator the power of reversing the current of electricity, so that the needles
are deflected with the utmost certainty to one side or the other, either separately
or simultaneously. (Fig. 213.)

Fig. 213.
The letters of the alphabet, figures, and a variety of conventional signals, are indicated by
the single and combined movements of the needles on the dial. The left-hand needle
moving once to the left indicates the +, which is given at the end of a word. Twice in the
same way, a; thrice, b; first right, then left, c; the reverse, d. Once direct to the right, e;
twice, f; thrice, g. In the same order with the other needle for h, i, k, l, m, n, o, p. The
signals below the centre of the dial are indicated by the parallel movements of both needles
simultaneously. Both needles moving once to the left indicate r; twice, s; thrice, t. First
right, then left with both, u; the reverse, v. Both moving once to the right, w; twice, x;
thrice, y. The figures are indicated in the same way as the letters nearest to which they are
respectively placed. To change from letters to figures the operator gives h, followed by the
+, which the recipient returns to signify that he understands. If, after the above signs (h and
+) were given, c r h l were received, 1845 would be understood. A change from figures to
letters is notified by giving i, followed by the +, which the recipient also returns. Each word
is acknowledged. If the recipient understand, he gives e; if not, the +, in which case the
word is repeated. Attention to a communication by this instrument is called by the ringing
of a bell (of any size), which is effected through the agency of an electric current. The
upper case contains the bell.

Sir W. O'Shaughnessy, in his excellent work on the electric telegraph in British
India, gives a description of a telegraphic instrument of remarkable simplicity,
which is successfully employed in India, and is highly spoken of by Mr. E. V.
Walker and other gentlemen practically acquainted with the working of
telegraphs. It consists of a coil of fine wire on a card or ivory frame, a magnetic
needle with a light index of paper pasted across it; two stops of thin sheet lead to
limit the vibrations of the index; a supporting board eight inches square, and a
square of glass in a frame of wood, or a common glass tumbler placed over it as

a shade, to prevent the index being moved by currents of air. It is stated that the
office boys, with the assistance of a native Indian carpenter, make up these
telegraphs at a price not exceeding two shillings each.
In England of course they would be more expensive; but the simplicity and
perfection of the arrangement are so much to be commended that we give the
details for the benefit of those boys who might wish to establish a telegraph on a
small scale for amusement.

THE FRAME.

This is a piece of mahogany eight inches square and one inch thick, with a
hollow groove cut in its centre two inches and a half long, half an inch wide, and
a quarter of an inch deep; a ledge of the same wood one inch wide and half an
inch deep surrounds the frame, leaving the inner surface seven inches square;
this is stained black with ink to make the motions of the index more
conspicuous.

THE COIL.

This consists of fifty feet of the finest silk-covered copper wire wound on a
frame of card two inches long, half an inch broad, three-eighths deep in the open
part.
An edge or flange of card, three-eighths of an inch wide, is attached to it at each
side to keep the wire in its place. The frame may be of thin wood or ivory, and
the winding of the wire commences at the lower left corner, and it is coiled from
left to right, as the hands of a watch would move in the same plane. (Fig. 214.)

Fig. 214.
The coil.

Two inches of each end of the coil wire are now stripped of their silk covering
by being rubbed with sand-paper. The coil is mounted in the frame by inserting

its lower edge or flange in the groove, so that the lower part or floor of the inside
of the coil is level with that of the frame, as shown below, and it is now ready to
receive the magnetized needle. (Fig. 215.)

Fig. 215.
The coil fitted into frame.

THE NEEDLE.

This is one inch long, one-twelfth of an inch wide, of the thinnest steel, and
fitted with a little brass cap turned to a true cone to receive the point on which it
is balanced. These needles are of hard tempered steel, and are magnetized by a
single contact with the poles of an electro-magnet or other ordinary powerful
magnet.
The magnet is now to be balanced on a steel point one-eighth of an inch high;
these are nipped off with cutting pliers from common sewing needles, and
soldered into a slip of thin copper three inches long, half an inch wide. (Fig.
216.)

Fig. 216.
a. The needle. b. The point on the slip of copper.

As the north end of the needle will be found to dip, it is advisable to counteract
this by touching the south end with a little shell-lac varnish, which dries rapidly,
and soon restores the needle to a perfect equilibrium.
The needle is completed for use by fixing to it an index of paper (cut from
glazed letter paper) two inches long, tapering from one-eighth of an inch to a

point, and fastened at right angles on to the needle with lac varnish, so as to be
truly balanced, and pointing the sharp end to the east, when the needle placed on
the point settles due north and south, its north pole being opposite the observer's
right hand, the observer facing west. (Fig. 217.)

Fig. 217.
The needle with the paper index.

The coil frame is placed north and south, and the needle is now introduced by
sliding the end of the slip of copper into the opening in the frame.
To limit the vibrations of the paper index a stop is placed at each side. The stops
are made of a strip of thin sheet-lead or copper, a quarter of an inch broad, one
inch and a half long, and turned up at a right angle, so that one inch rests on the
board and half an inch is vertical. For ordinary practice these stops are placed
each at half an inch from the index.
The telegraph is placed in a box, which may have a piece of looking-glass in the
lid, so that the readings can be taken with the needle in the vertical instead of the
horizontal position, if required. (Fig. 218.)

Fig. 218.
Box containing the telegraph, with the looking-glass in the lid. A small steel magnet is
placed on or near the frame, if required, the south pole of this magnet being opposite to the
north pole of the needle in the telegraph coil. The bar is four inches long, half an inch
broad, three-sixteenths of an inch thick, and it is only used to counteract any local deviation
which may arise in using the instrument with miles of wire. It would not be required under
ordinary circumstances. The alphabet used is shown to the left.

The ends of the fine wire of the telegraph coil are joined on to the wires from the
reversing instrument, and this is connected with a voltaic series of one or more
elements, so that by the employment of the reverser the needle is caused to move
right or left at pleasure. The white paper index on the black ground can be
followed with the greatest certainty, and Sir W. O'Shaughnessy states that with
this instrument a telegraph clerk may read at the rate of twenty words per minute
with a double needle wire, being equal to forty words per minute.

THE REVERSER

consists of a block of wood, two inches and a half square, in which four hollows,
half an inch deep, are cut, and these hollows are joined diagonally by copper
wires let into the substance of the wood, and most carefully insulated from each
other by melted cement, but exposing a clean metallic surface in each cell,
which is filled with mercury. (Fig. 219.)

Fig. 219.
Block of wood with four holes; the positive terminal is connected with the holes a and b,
the negative with c and d; the hollows are filled with mercury. t t are the wires from the
telegraph box, and it is obvious that by dipping them alternately into c b and a d the current
is reversed, and the needle deflected right or left at pleasure.

In practice a more elaborate reverser is employed, but to demonstrate the
principle the simple block above described is quite sufficient.
With the telegraph placed at the top of a house, or in a distant cottage, and a
single cell of Grove's battery, or at most two, for any short distances, with the
reverser, messages may be passed with great rapidity from the bottom of the
house to the top, or from a mansion to the lodge, it being understood that a
battery, reverser, and telegraph, are required at both places where messages are
received and answered; but if no answers are required, the battery and reverser
are placed at one end of the wire in the house, and the telegraph at the other
extremity in the cottage, and earth plates may be arranged to return the current,
or another wire used for that purpose.
Whilst lauding to the utmost the invention of the electric telegraph, we must
remember "there is nothing new under the sun," and that after all Nature claims
the principle of telegraphing, and with the silent gesture, the speaking eye,
interpreted and answered by others, she proclaims herself to be the originator of
communication by signs. Whilst the language of flowers, and the mournful
requirements of the deaf and dumb in the use of the finger alphabet, show how
readily man has adopted the important principle, till he has brought it to the
highest state of perfection in the electric telegraph.

When the telegraph was first adopted on the Great Western Railway, the most
ridiculous ideas were formed of its capabilities, and many persons firmly
believed that the wires were used for the purpose of dragging letters and
different articles from station to station. "Wife," said a man, looking at the
telegraph wires, "I don't see, for my part, how they send letters on them wires,
without tearin' 'em all to bits." "Oh, you stupid!" exclaimed his intellectual
spouse; "why, they don't send the paper: they just send the writin' in a fluid
state."

Fig. 220.
One of the ideas of telegraphic communication.

CHAPTER XVIII.
RUHMKORFF'S, HEARDER'S, AND BENTLEY'S COIL
APPARATUS.

In the course of the popular articles on frictional and voltaic electricity, it has
already been mentioned that whilst the intensity effects—such as the capability
of the spark to pass through a certain thickness of air, or the production of the
peculiar physiological effect of the shock—belong especially to the phenomena
of frictional electricity, they are not apparent with the quantity effects, such as
may be produced by an ordinary voltaic battery, unless the latter consists of an
immense number of elements, such as the famous water battery of the late
respected Mr. Crosse, which consisted of two thousand five hundred pairs of
copper and zinc cylinders, well insulated on glass stands, and protected from
dust and light. If, however, the feeble intensity current of voltaic electricity, from
four or five elements, is permitted to pass into a coil of a peculiar construction,
fitted with a condenser, and manufactured either by Ruhmkorff of Paris, or Mr.
Hearder of Plymouth, then the most remarkable effects are producible, which
have created quite a new and distinct series of phenomena, and further
established in the most satisfactory manner the connexion between the
electricities derived from friction and chemical action.
The construction of these coils does not differ very materially, and great merit is
due to Messrs. Ruhmkorff, Hearder, and Bentley, who have separately and
independently worked out the construction of the most formidable machines of
this class. In a letter to the author Mr. Bentley says:—
"I commence the formation of my coil by using as an axis an iron tube ten
inches long and half an inch diameter; around this is placed a considerable
number of insulated iron wires the same length as the tube, and sufficiently
numerous to form a bundle one inch and three quarters diameter. This core is
wrapped carefully in eight or nine layers of waxed silk, the necessity of which
will be obvious presently.
"My primary helix, which is formed of thirty yards of No. 14 cotton-covered
copper wire, is wound carefully on this core, and consists of two layers, each
layer being carefully insulated one from the other by waxed silk, for I find that if

a wet string or fine platinum wire be connected with the two ends of the primary
wires of an induction coil in action, there is scarcely an indication of an induced
current to be obtained from the secondary wire. That this is not owing to any
decrease of magnetic power is proved by testing the iron core before and after
the experiment, but is simply owing to the central magnet or coil exerting the
whole of its inductive powers upon the nearest closed circuit; it therefore follows
that if the two layers of primary wire are connected by the cotton covering
becoming moist, the whole of the induced current will take this path instead of
traversing the secondary wire.
"Before describing my secondary wire I must again call attention to the
important fact that the magnetism of the iron exerts its inductive power upon the
nearest conducting medium; and I have constructed an instrument to
demonstrate this fact. It consists simply of an ordinary coil, giving the third of
an inch spark, but having the four inner layers of secondary wire brought out
separately. Now, I find that when I keep the ends of this wire separate I obtain
nearly the third of an inch spark, but when I connect them metallically I can
obtain no intensity spark whatever from the seventeen coils which surround
them.
"It follows from this that before winding the secondary wire the striking distance
of a single layer must be ascertained, and I find that with my coil I can get a
spark one-tenth of an inch long from one coil of wire, and sufficiently intense to
penetrate with facility six layers of waxed silk.
"Waxed silk is therefore unsuited for the insulation of large coils, and I find,
after numerous experiments, that there is no substance so fitted for the purpose
as gutta-percha tissue, and I use five layers of this substance to each layer of
wire.
"The secondary helix then consists of three thousand yards of No. 35 silk-
covered copper wire, and is insulated in the manner described above; but as I do
not use cheeks to my coil it assumes the form of a cylinder having rounded ends.
"For the protection of this instrument I place it in a mahogany box of the proper
size, and it is supported and retained in its position by an iron rod, which is
thrust through the hollow axis of the core and the two ends of the box, leaving
half an inch of the iron projecting to work the contact breaker, which is fixed to
one end of the box, while the two ends of the secondary wire are brought out of
the other through gutta percha tubes.

"The condenser is contained in a separate box, and is formed of one hundred and
twenty sheets of tinfoil between double that number of sheets of varnished
paper, the alternate sides of the foil being brought out and connected to
appropriate binding screws.
"This condenser forms a convenient stand for the coil, and can be used for many
interesting experiments."
The shock which the condenser gives to the system depends in a great measure
on the size of the coatings. The primary wire alone does not produce any
physiological results, or at least very feeble ones. Mr. Hearder's coil is wound on
a bobbin six inches in length, and four inches and a half thick, and includes three
thousand yards of covered wire (No. 35). The iron core consists of a bundle of
small wires capped with solid ends, and the sparks obtained from it were five-
eighths of an inch in air when the primary coil was excited by four pairs of
Grove's series; and when connected with the Leyden jar, the most vigorous and
brilliant results were produced. The condenser is made of cartridge paper, coated
in the proper manner with tinfoil. The secondary coil is quite independent of the
primary one, which is laid on in different lengths, so that the coil can be adjusted
to any battery power, whether for quantity or intensity.
For the successful exhibition of the capabilities of the machine, it is required to
perform the experiments in a darkened room. (Fig. 221.)

Fig. 221.
Ruhmkorff's apparatus. a b. The coil, containing more than a mile of insulated wire. The
stand it rests upon, and with which it is in communication, contains the condenser.

In using this apparatus, eight pairs of Grove's battery will be quite sufficient to
produce the effects, and the greatest care must be taken to avoid the shock,
which is most severe and painful, and might do a great deal of harm to a weakly,
sensitive, and nervous person. To avoid any accidents of this kind, the
convenient arrangement at one end shown in Fig. 222 must be carefully attended

to, and when manipulating with any part of the apparatus, if the battery is
attached, the contact should first be broken by bringing the ivory (the non-
conducting) part of the cylinder a (Fig. 222) in communication with the
conductors, b b, where the wires from the battery are attached.

Fig. 222.
One end of Ruhmkorff's coil. b b. Connexion to receive the battery wires. a is the cylinder,
one half of which is ivory and the other metal. In this position no shock can be received,
because the electricity is cut off by the ivory from the coil.

First Experiment.

It is at the other extremity of the coil that the experiments are performed; for
instance, if an exhausted globe is connected with the pillars b b (Fig. 223), and
the connexion made with the battery, a beautiful faint blue light is apparent on
one of the knobs and wires, and by reversing the current the light appears on the
other knob and wire. This effect is supposed to resemble some of those
magnificent streaks and undulations of coloured light called the Aurora Borealis;
and, if the globe is removed from the foot, and screwed on to the air-pump plate,
and a little alcohol, ether, naphtha, or turpentine placed on wool or tow is held to
the air-pump screw, where the air usually rushes in, and the cock turned, so that
the vacuum is destroyed, a quantity of the vapour will necessarily fill the globe;
and if this is once more exhausted, it presents a different appearance, being full
of coloured light (varying according to the spirit employed) but stratified and of
a circular form. (Fig. 223.)

Fig. 223.
End of coil where the experiments are performed. b b. Connecting screws and wires
passing to the exhausted globe, c. The screws are supported on insulating glass pillars, p p.

Second Experiment.

The appearance of these bands of light is modified by the nature of the glass
tubes employed, and the subject has been carefully investigated by Mr. Gassiott.
At the last meeting of the British Association at Aberdeen, Dr. Robinson made
various experiments, arranged by Mr. Ladd, for the purpose of showing the
connexion between these miniature effects of bands of light in tubes containing
various gases, and the phenomena of the Aurora Borealis. The title of the
discourse, which was specially delivered in the Music Hall by the learned
Doctor, was "On Electrical Discharges in Highly-rarefied Media," and it was
illustrated by experiments prepared by Mr. Gassiott and Mr. Ladd.
The kind of tubes employed may be understood from the next figure. They are
made in Germany, and by approaching a powerful magnet to the outside of any
of the glass tubes whilst the bands of light are being produced, the most
remarkable modifications of them are obtained. Mr. Ladd has mounted one of
these tubes in a rotatory arrangement similar to that described at page 186.page
186 When connected with the coil and battery, it furnishes one of the most
lovely "electric fire-wheels" that can possibly be described. (Fig. 224.) Mr.
Grove placed a piece of carefully-dried phosphorus in a little metallic cup, and

covered it with a jar having a cap and wire. On removing the air from the
receiver, and passing the current of electricity through it from the Ruhmkorff
coil, he obtained a light completely stratified, and blended transversely with
straight but vibrating dark bands.

Fig. 224.
a, b, c, d, e, f. Various tubes of different kinds of glass, and containing gases and vapours.
Each tube has a platinum wire inserted at both ends, with which the contact is made with
the coil. The tube a contains mercury, which has been boiled in it, and the air expelled. By
moving the conducting wire to g or h, the light which otherwise passes through the whole
of the tubes stops at these points.

Third Experiment.

When two very thin iron wires are arranged in the upright pillars (Fig. 223), and
held sufficiently close to each other, as in Fig. 225, light passes from one to the
other. The wire from which the light passes remains cold, the other becomes so
hot that it melts into a little globule of liquid iron, and if paper is held between
the wires it rapidly takes fire. (Fig. 225.)

Fig. 225.
Melting of the iron wire.

Fourth Experiment.

Remove the break. Attach two wires to x x (Fig. 226). Hold them so as at
pleasure to complete and interrupt the galvanic circle. Two other wires are
attached at p p, their ends being about three-quarters of an inch asunder. When
the current is closed or broken at a a, a spark passes between b b. (Fig. 226.)

Fig. 226.
The making and breaking of the circuit.

Fifth Experiment.

A Leyden jar may be charged and discharged with singular rapidity when
connected with the coil, and the snapping noise is so rapid, that it produces a
continuous sharp sound. (Fig. 227.) If a piece of paper is held between the ball
of the Leyden jar and the wire, it is instantly perforated, but not set on fire.

Fig. 227.
a b. Leyden jar coated with tinfoil, and standing on any non-conductor, such as gutta
percha or the resinous or glass plate, c.

Sixth Experiment.

When the Leyden jar is coated with spangles of tinfoil, a spark appears at each
break, and the whole jar is lit up with hundreds of brilliant sparks each time it is
charged and discharged, and as this occurs with amazing rapidity, the light is
almost continuous. (No. 1. Fig. 228.) The larger the Leyden jar, the shorter the
spark, and vice versâ. By the employment of a nicely-made screw and inch-
scale, the distance between the discharging points connected with a Leyden jar
can be accurately determined; and Mr. Hearder states that supposing a Leyden
jar has one square foot of charging surface, it will give a spark of one inch in
length, but if a smaller jar is used, with only half a square foot of charging
surface, the spark would be about one inch and a quarter in length. (Fig. 228.)

Fig. 228.
No. 1. Spangled Leyden jar. No. 2. Hoarder's apparatus for measuring the length of spark
for Leyden jar and coil. p p. Glass pillars. No. 3. Two best forms of spangles to paste on a
Leyden jar.

Seventh Experiment.

The direction and rapidity of the current appear to influence greatly the heating
and fire-giving power of the coil, and the following experiment, devised by Mr.
Hearder, furnishes a curious illustration of this fact.
When the current passes in the direction of the arrows (Fig. 229), the platinum
wire remains perfectly cool whilst the gunpowder is fired; and the contrary takes
place if the current is reversed—viz., the gunpowder does not blow up, but the
platinum wire is heated. In the second experiment, a Leyden jar is included in
the circuit. (Fig. 229.)

Fig. 229.
a. The coil. b. Hearder's discharger, with thin platinum wire, p, hanging between the points.
c. Another discharger, and powder going off between the points from the little table. The
pillars of the dischargers are glass. The arrows show the direction of the current of
electricity.

Eighth Experiment.

Amongst so many beautiful experiments, it is somewhat difficult to say which is
the most pleasing, but for softness and exquisite colouring, with the continuous
vibrating motion of the flowing current of electricity, nothing can surpass "the
cascade experiment." [This beautiful experiment is usually termed "Gassiott's
Cascade," and is thus described by that gentleman. Two-thirds of a beaker glass,
four inches deep by two inches, are coated with tinfoil, leaving one inch and a
half of the upper part uncoated. On the plate of an air-pump is placed a glass
plate, and over it the beaker, covering the whole with an open-mouthed glass
receiver, on which is placed a brass plate having a thick wire passing through a
collar of leather; the portion of the wire within the receiver is covered with a
glass tube; one end of the secondary coil is attached to this wire, and the other to
the plate of the pump. As the vacuum improves the effect is very surprising; at
first a faint clear blue light appears to proceed from the lower part of the beaker
to the plate; this gradually becomes brighter, until by slow degrees it rises,
increasing in brilliancy until it arrives at that part which is opposite, or on a line
with the inner coating, the whole being intensely illuminated; a discharge then
commences, as if the electric fluid were itself a material body running over.]
This result is obtained by coating the inside of a handsome glass goblet with
tinfoil, and placing it under a jar fitted with a collar of leather and ball, and
arranged in the usual manner on the air-pump. Directly a vacuum is obtained,
the ball is moved down to the inside of the goblet, and the wires from the coil
being attached, a continuous series of streams of electric light seem to overflow