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Title: The Complete Works in Philosophy, Politics and Morals of the
late Dr. Benjamin Franklin, Vol. 2 [of 3]

Author: Benjamin Franklin

Release date: February 2, 2015 [eBook #48137]
Most recently updated: October 24, 2024

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*** START OF THE PROJECT GUTENBERG EBOOK THE
COMPLETE WORKS IN PHILOSOPHY, POLITICS AND MORALS OF
THE LATE DR. BENJAMIN FRANKLIN, VOL. 2 [OF 3] ***

TRANSCRIBER'S NOTE
This is Volume 2 of a 3-volume set. The other two volumes are also accessible in Project
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Obvious typographical errors and punctuation errors have been corrected after careful
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Th e

WORKS
Of

Benjamin Franklin, L.L.D.
VOL. 2.

W&G Cooke Sculptor

Printed,
for Longman, Hurst, Rees, & Orme, Paternoster Row, London.

THE

COMPLETE

WORKS,
IN

PHILOSOPHY, POLITICS, AND MORALS,

OF THE LATE

DR. BENJAMIN FRANKLIN,
NOW FIRST COLLECTED AND ARRANGED:
WITH

MEMOIRS OF HIS EARLY LIFE,
WRITTEN BY HIMSELF.

IN THREE VOLUMES.

VOL. II.

London:
P RINTED F O R J. J O H NS O N, S T. PAUL' S CH URCH - YARD;
AND LO NG MAN, H URS T, REES AND O RME,

PATERNO S TER- RO W.

———

1806.

J. CUN DE E , P R I NT E R
L ON DON

CONTENTS.

VOL. II.

LETTERS AND PAPERS ON PHILOSOPHICAL SUBJECTS.
Physical and meteorological observations, conjectures and suppositions 1
On water-spouts 11
The same subject continued 13
Water-spouts and whirlwinds compared 19
Description of a water-spout at Antigua 34
Shooting stars 36
Water-spouts and whirlwinds 37
Observations on the meteorological paper; by a gentleman in Connecticut 45
Observations in answer to the foregoing, by B. Franklin 49
Observations on the meteorological paper; sent by a gentleman in New York to
B. Franklin 51
Answer to the foregoing observations, by B. Franklin 55
Gentleman of New York in reply 58
Account of a whirlwind at Maryland 61
On the north east storms in North America 63
Meteorological imaginations and conjectures 66
Suppositions and conjectures towards forming an hypothesis, for the
explanation of the aurora borealis 69
On cold produced by evaporation 75
On the same subject 83
Concerning the light in sea-water 88
On the saltness of sea-water 91
On the effect of air on the barometer, and the benefits derived from the study of
insects 92
On the Bristol waters, and the tide in rivers 95
On the same subject 102
Salt-water rendered fresh by distillation.—Method of relieving thirst by sea-
water 103
Tendency of rivers to the sea.—Effect of the sun's rays on cloth of different
colours 105
On the vis inertiæ of matter 110
On the different strata of the earth 116

On the theory of the earth 117
New and curious theory of light and heat 122
Queries and conjectures relating to magnetism and the theory of the earth 125
On the nature of sea coal 125
Effect of vegetation on noxious air 129
On the inflammability of the surface of certain rivers in America 130
On the different quantities of rain which fall at different heights over the same
ground 133
Slowly sensible hygrometer proposed, for certain purposes 135
Curious instance of the effect of oil on water 142
Letters on the stilling of waves by means of oil 144
Extract of a letter from Mr. Tengnagel to Count Bentinck, dated at Batavia, the
5th of January, 1770 154
On the difference of navigation in shoal and deep water 158
Sundry maritime observations 162
Remarks upon the navigation from Newfoundland to New-York, in order to
avoid the Gulph Stream on one hand, and on the other the shoals that lie to
the southward of Nantucket and of St. George's Banks 197
Observations of the warmth of the sea-water, &c. by Fahrenheit's
Thermometer, in crossing the Gulph Stream; with other remarks made on
board the Pensylvania packet, Capt. Osborne, bound from London to
Philadelphia, in April and May, 1775 199
Observations of the warmth of the sea-water, &c. by Fahrenheit's thermometer;
with other remarks made on board the Reprisal, Capt. Wycks, bound from
Philadelphia to France, in October and November, 1776 200
A journal of a voyage from the Channel between France and England towards
America 202
On the art of swimming 206
On the same subject, in answer to some enquiries of M. Dubourg 210
On the free use of air 213
On the causes of colds 214
Dr. Stark, and Dr. Letsom 215
Number of deaths in Philadelphia by inoculation ibid
Answer to the preceding 217
On the effects of lead upon the human constitution 219
Observations on the prevailing doctrines of life and death 222
An account of the new-invented Pensylvanian fire-places 225
On the causes and cure of smoky chimneys 256
Description of a new stove for burning of pitcoal, and consuming all its smoke 296
Method of contracting chimneys.—Modesty in disputation 317
Covering houses with copper 318
On the same subject 320
Paper referred to in the preceding letter 322
Magical square of squares 324
Magical circle 328
New musical instrument composed of glasses 330

Best mediums for conveying sound 335
On the harmony and melody of the old Scotch tunes 338
On the defects of modern music 343
Description of the process to be observed in making large sheets of paper in the
Chinese manner, with one smooth surface 349
On modern innovations in the English language and in printing 351
A scheme for a new alphabet and reformed mode of spelling; with remarks and
examples concerning the same; and an enquiry into its uses, in a
correspondence between Miss S—— and Dr. Franklin, written in the
characters of the alphabet 357
Rules for a club formerly established in Philadelphia 366
Questions discussed by the Junto forming the preceding club 369
Sketch of an English school; for the consideration of the trustees of the
Philadelphia Academy 370
Advice to youth in reading 378

PAPERS ON SUBJECTS OF GENERAL POLITICS.
Observations concerning the increase of mankind, peopling of countries, &c 383
Remarks on some of the foregoing observations, showing particularly the
effect which manners have on population 392
Plan by Messieurs Franklin and Dalrymple, for benefiting distant unprovided
countries 403
Concerning the provision made in China against famine 407
Positions to be examined, concerning national wealth 408
Political fragments, supposed either to be written by Dr. Franklin, or to contain
sentiments nearly allied to his own 411
On the price of corn, and management of the poor 418
On luxury, idleness, and industry 424
On smuggling, and its various species 430
Observations on war 435
Notes copied from Dr. Franklin's writing in pencil in the margin of Judge
Foster's celebrated argument in favour of the impressing of seamen 437
On the criminal laws, and the practice of privateering 441
A parable against persecution, in imitation of scripture language 450
A letter concerning persecution in former ages, the maintenance of the clergy,
American bishops, and the state of toleration in Old England and New
England compared 452
On the slave trade 459
Account of the highest court of judicature in Pensylvania, viz. The court of the
press 463

LIST OF THE PLATES

PLATE V. Water-Spouts facing page 16
PLATE VI. Maritime Observations 163
PLATE VII. A Chart of the Gulph Stream 197
PLATE VIII. Pensylvania Fire-Place 235
PLATE VIII*. Profile of the Pensylvania Chimnie 238
PLATE IX. Remedies for Smoky Chimnies 269
PLATE X. Stove for Burning Pit-Coal 297
PLATE XI. A Magic Square of Squares 327
PLATE XII. A Magic Circle of Circles 328

ERRATA.

Page. Line.
117 penult. for preceding day, read the preceding day.
254 17: for the annexed cut, read Plate VIII.
276 11: for Plate I, read Plate IX.
293 23: for Fig. 13, read Fig. 10.
318 9: for descent, read decent.
326 5: for Plate XI, read Plate V. Fig. 3.

LETTERS AND PA P E R S
ON

PHILOSOPHICAL SUBJECTS.

LETTERS AND PAPERS
ON

PHILOSOPHICAL SUBJECTS.

Physical and Meteorological Observations, Conjectures and Suppositions.

Read at the Royal Society, June 3, 1756.

The particles of air are kept at a distance from each other by their mutual
repulsion.
Every three particles, mutually and equally repelling each other, must
form an equilateral triangle.
All the particles of air gravitate towards the earth, which gravitation
compresses them, and shortens the sides of the triangles, otherwise their
mutual repellency would force them to greater distances from each other.
Whatever particles of other matter (not endued with that repellency) are
supported in air, must adhere to the particles of air, and be supported by
them; for in the vacancies there is nothing they can rest on.

Air and water mutually attract each other. Hence water will dissolve in
air, as salt in water.
The specific gravity of matter is not altered by dividing the matter,
though the superficies be increased. Sixteen leaden bullets, of an ounce
each, weigh as much in water as one of a pound, whose superficies is less.
Therefore the supporting of salt in water is not owing to its superficies
being increased.
A lump of salt, though laid at rest at the bottom of a vessel of water, will
dissolve therein, and its parts move every way, till equally diffused in the
water; therefore there is a mutual attraction between water and salt. Every
particle of water assumes as many of salt as can adhere to it; when more is
added, it precipitates, and will not remain suspended.
Water, in the same manner, will dissolve in air, every particle of air
assuming one or more particles of water. When too much is added, it
precipitates in rain.
But there not being the same contiguity between the particles of air as of
water, the solution of water in air is not carried on without a motion of the
air, so as to cause a fresh accession of dry particles.
Part of a fluid, having more of what it dissolves, will communicate to
other parts that have less. Thus very salt water, coming in contact with
fresh, communicates its saltness till all is equal, and the sooner if there is a
little motion of the water.
Even earth will dissolve, or mix with air. A stroke of a horse's hoof on the
ground, in a hot dusty road, will raise a cloud of dust, that shall, if there be a
light breeze, expand every way, till, perhaps, near as big as a common
house. It is not by mechanical motion communicated to the particles of dust
by the hoof, that they fly so far, nor by the wind, that they spread so wide:
but the air near the ground, more heated by the hot dust struck into it, is
rarefied and rises, and in rising mixes with the cooler air, and communicates
of its dust to it, and it is at length so diffused as to become invisible.
Quantities of dust are thus carried up in dry seasons: showers wash it from
the air, and bring it down again. For water attracting it stronger, it quits the
air, and adheres to the water.

Air, suffering continual changes in the degrees of its heat, from various
causes and circumstances, and, consequently, changes in its specific gravity,
must therefore be in continual motion.
A small quantity of fire mixed with water (or degree of heat therein) so
weakens the cohesion of its particles, that those on the surface easily quit it,
and adhere to the particles of air.
A greater degree of heat is required to break the cohesion between water
and air.
Air moderately heated will support a greater quantity of water invisibly
than cold air; for its particles being by heat repelled to a greater distance
from each other, thereby more easily keep the particles of water that are
annexed to them from running into cohesions that would obstruct, refract,
or reflect the light.
Hence when we breathe in warm air, though the same quantity of
moisture may be taken up from the lungs, as when we breathe in cold air,
yet that moisture is not so visible.
Water being extremely heated, i.e. to the degree of boiling, its particles in
quitting it so repel each other, as to take up vastly more space than before,
and by that repellency support themselves, expelling the air from the space
they occupy. That degree of heat being lessened, they again mutually
attract, and having no air-particles mixed to adhere to, by which they might
be supported and kept at a distance, they instantly fall, coalesce, and
become water again.
The water commonly diffused in our atmosphere never receives such a
degree of heat from the sun, or other cause, as water has when boiling; it is
not, therefore, supported by such heat, but by adhering to air.
Water being dissolved in, and adhering to air, that air will not readily take
up oil, because of the mutual repellency between water and oil.
Hence cold oils evaporate but slowly, the air having generally a quantity
of dissolved water.
Oil being heated extremely, the air that approaches its surface will be also
heated extremely; the water then quitting it, it will attract and carry off oil,

which can now adhere to it. Hence the quick evaporation of oil heated to a
great degree.
Oil being dissolved in air, the particles to which it adheres will not take
up water.
Hence the suffocating nature of air impregnated with burnt grease, as
from snuffs of candles and the like. A certain quantity of moisture should be
every moment discharged and taken away from the lungs; air that has been
frequently breathed, is already overloaded, and, for that reason, can take no
more, so will not answer the end. Greasy air refuses to touch it. In both
cases suffocation for want of the discharge.
Air will attract and support many other substances.
A particle of air loaded with adhering water, or any other matter, is
heavier than before and would descend.
The atmosphere supposed at rest, a loaded descending particle must act
with a force on the particles it passes between, or meets with, sufficient to
overcome, in some degree, their mutual repellency, and push them nearer to
each other.
Thus, supposing the particles A B C D, and the
other near them, to be at the distance caused by
their mutual repellency (confined by their common
gravity) if A would descend to E, it must pass
between B and C; when it comes between B and C,
it will be nearer to them than before, and must
either have pushed them nearer to F and G,
contrary to their mutual repellency, or pass through
by a force exceeding its repellency with them. It
then approaches D, and, to move it out of the way,
must act on it with a force sufficient to overcome
its repellency with the two next lower particles, by which it is kept in its
present situation.
Every particle of air, therefore, will bear any load inferior to the force of
these repulsions.
Hence the support of fogs, mists, clouds.

Very warm air, clear, though supporting a very great quantity of moisture,
will grow turbid and cloudy on the mixture of a colder air, as foggy turbid
air will grow clear by warming.
Thus the sun shining on a morning fog, dissipates it; clouds are seen to
waste in a sun-shiny day.
But cold condenses and renders visible the vapour; a tankard or decanter
filled with cold water will condense the moisture of warm clear air on its
outside, where it becomes visible as dew, coalesces into drops, descends in
little streams.
The sun heats the air of our atmosphere most near the surface of the
earth; for there, besides the direct rays, there are many reflections.
Moreover, the earth itself being heated, communicates of its heat to the
neighbouring air.
The higher regions, having only the direct rays of the sun passing through
them, are comparatively very cold. Hence the cold air on the tops of
mountains, and snow on some of them all the year, even in the torrid zone.
Hence hail in summer.
If the atmosphere were, all of it (both above and below) always of the
same temper as to cold or heat, then the upper air would always be rarer
than the lower, because the pressure on it is less; consequently lighter, and
therefore would keep its place.
But the upper air may be more condensed by cold, than the lower air by
pressure; the lower more expanded by heat, than the upper for want of
pressure. In such case the upper air will become the heavier, the lower the
lighter.
The lower region of air being heated and expanded heaves up, and
supports for some time the colder heavier air above, and will continue to
support it while the equilibrium is kept. Thus water is supported in an
inverted open glass, while the equilibrium is maintained by the equal
pressure upwards of the air below; but the equilibrium by any means
breaking, the water descends on the heavier side, and the air rises into its
place.
The lifted heavy cold air over a heated country, becoming by any means
unequally supported, or unequal in its weight, the heaviest part descends

first, and the rest follows impetuously. Hence gusts after heats, and
hurricanes in hot climates. Hence the air of gusts and hurricanes cold,
though in hot climes and seasons; it coming from above.
The cold air descending from above, as it penetrates our warm region full
of watry particles, condenses them, renders them visible, forms a cloud
thick and dark, overcasting sometimes, at once, large and extensive;
sometimes, when seen at a distance, small at first, gradually increasing; the
cold edge, or surface of the cloud, condensing the vapours next it, which
form smaller clouds that join it, increase its bulk, it descends with the wind
and its acquired weight, draws nearer the earth, grows denser with continual
additions of water, and discharges heavy showers.
Small black clouds thus appearing in a clear sky, in hot climates, portend
storms, and warn seamen to hand their sails.
The earth, turning on its axis in about twenty-four hours, the equatorial
parts must move about fifteen miles in each minute; in northern and
southern latitudes this motion is gradually less to the poles, and there
nothing.
If there was a general calm over the face of the globe, it must be by the
air's moving in every part as fast as the earth or sea it covers.
He that sails, or rides, has insensibly the same degree of motion as the
ship or coach with which he is connected. If the ship strikes the shore, or
the coach stops suddenly, the motion continuing in the man, he is thrown
forward. If a man were to jump from the land into a swift sailing ship, he
would be thrown backward (or towards the stern) not having at first the
motion of the ship.
He that travels by sea or land, towards the equinoctial, gradually acquires
motion; from it, loses.
But if a man were taken up from latitude 40 (where suppose the earth's
surface to move twelve miles per minute) and immediately set down at the
equinoctial, without changing the motion he had, his heels would be struck
up, he would fall westward. If taken up from the equinoctial, and set down
in latitude 40, he would fall eastward.
The air under the equator, and between the tropics, being constantly
heated and rarefied by the sun, rises. Its place is supplied by air from

northern and southern latitudes, which coming from parts where the earth
and air had less motion, and not suddenly acquiring the quicker motion of
the equatorial earth, appears an east wind blowing westward; the earth
moving from west to east, and slipping under the air[1].
Thus, when we ride in a calm, it seems a wind against us: if we ride with
the wind, and faster, even that will seem a small wind against us.
The air rarefied between the tropics, and rising, must flow in the higher
region north and south. Before it rose, it had acquired the greatest motion
the earth's rotation could give it. It retains some degree of this motion, and
descending in higher latitudes, where the earth's motion is less, will appear
a westerly wind, yet tending towards the equatorial parts, to supply the
vacancy occasioned by the air of the lower regions flowing thitherwards.
Hence our general cold winds are about north west, our summer cold
gusts the same.
The air in sultry weather, though not cloudy, has a kind of haziness in it,
which makes objects at a distance appear dull and indistinct. This haziness
is occasioned by the great quantity of moisture equally diffused in that air.
When, by the cold wind blowing down among it, it is condensed into
clouds, and falls in rain, the air becomes purer and clearer. Hence, after
gusts, distant objects appear distinct, their figures sharply terminated.
Extreme cold winds congeal the surface of the earth, by carrying off its
fire. Warm winds afterwards blowing over that frozen surface will be
chilled by it. Could that frozen surface be turned under, and a warmer
turned up from beneath it, those warm winds would not be chilled so much.
The surface of the earth is also sometimes much heated by the sun: and
such heated surface not being changed heats the air that moves over it.
Seas, lakes, and great bodies of water, agitated by the winds, continually
change surfaces; the cold surface in winter is turned under by the rolling of
the waves, and a warmer turned up; in summer, the warm is turned under,
and colder turned up. Hence the more equal temper of sea-water, and the air
over it. Hence, in winter, winds from the sea seem warm, winds from the
land cold. In summer the contrary.

Therefore the lakes north-west of us[2], as they are not so much frozen,
nor so apt to freeze as the earth, rather moderate than increase the coldness
of our winter winds.
The air over the sea being warmer, and therefore lighter in winter than
the air over the frozen land, may be another cause of our general N. W.
winds, which blow off to sea at right angles from our North-American
coast. The warm light sea air rising, the heavy cold land air pressing into its
place.
Heavy fluids descending, frequently form eddies, or whirlpools, as is
seen in a funnel, where the water acquires a circular motion, receding every
way from a centre, and leaving a vacancy in the middle, greatest above, and
lessening downwards, like a speaking trumpet, its big end upwards.
Air descending, or ascending, may form the same kind of eddies, or
whirlings, the parts of air acquiring a circular motion, and receding from the
middle of the circle by a centrifugal force, and leaving there a vacancy; if
descending, greatest above, and lessening downwards; if ascending, greatest
below, and lessening upwards; like a speaking trumpet, standing its big end
on the ground.
When the air descends with violence in some places, it may rise with
equal violence in others, and form both kinds of whirlwinds.
The air in its whirling motion receding every way from the centre or axis
of the trumpet leaves there a vacuum, which cannot be filled through the
sides, the whirling air, as an arch, preventing; it must then press in at the
open ends.
The greatest pressure inwards must be at the lower end, the greatest
weight of the surrounding atmosphere being there. The air entering rises
within, and carries up dust, leaves, and even heavier bodies that happen in
its way, as the eddy, or whirl, passes over land.
If it passes over water, the weight of the surrounding atmosphere forces
up the water into the vacuity, part of which, by degrees, joins with the
whirling air, and adding weight, and receiving accelerated motion, recedes
still farther from the centre or axis of the trump, as the pressure lessens; and
at last, as the trump widens, is broken into small particles, and so united

with air as to be supported by it, and become black clouds at the top of the
trump.
Thus these eddies may be whirlwinds at land, water-spouts at sea. A body
of water so raised, may be suddenly let fall, when the motion, &c. has not
strength to support it, or the whirling arch is broken so as to admit the air:
falling in the sea, it is harmless, unless ships happen under it; but if in the
progressive motion of the whirl it has moved from the sea, over the land,
and then breaks, sudden, violent, and mischievous torrents are the
consequences.
B. FRANKLIN.

FOOTNOTES:

[1] See a paper on this subject, by the late ingenious Mr. Hadley, in the
Philosophical Transactions, wherein this hypothesis for explaining the trade-
winds first appeared.
[2] In Pensylvania.

DOCTOR ——[3] OF BOSTON, TO BENJAMIN FRANKLIN, ESQ.
AT P H I L A D E L P H I A .

On Water-Spouts.

Read at the Royal Society, June 3, 1756.

Boston, October 16, 1752.
Sir,
I find by a word or two in your last[4], that you are willing to be found
fault with; which authorises me to let you know what I am at a loss about in
your papers, which is only in the article of the water-spout. I am in doubt,
whether water in bulk, or even broken into drops, ever ascends into the
region of the clouds per vorticem; i. e. whether there be, in reality, what I
call a direct water-spout. I make no doubt of direct and inverted whirl-

winds; your description of them, and the reason of the thing, are sufficient. I
am sensible too, that they are very strong, and often move considerable
weights. But I have not met with any historical accounts that seem exact
enough to remove my scruples concerning the ascent abovesaid.
Descending spouts (as I take them to be) are many times seen, as I take it,
in the calms, between the sea and land trade-winds on the coast of Africa.
These contrary winds, or diverging, I can conceive may occasion them, as it
were by suction, making a breach in a large cloud. But I imagine they have,
at the same time, a tendency to hinder any direct or rising spout, by carrying
off the lower part of the atmosphere as fast as it begins to rarefy; and yet
spouts are frequent here, which strengthens my opinion, that all of them
descend.
But however this be, I cannot conceive a force producible by the
rarefication and condensation of our atmosphere, in the circumstances of
our globe, capable of carrying water, in large portions, into the region of the
clouds. Supposing it to be raised, it would be too heavy to continue the
ascent beyond a considerable height, unless parted into small drops; and
even then, by its centrifugal force, from the manner of conveyance, it would
be flung out of the circle, and fall scattered, like rain.
But I need not expatiate on these matters to you. I have mentioned my
objections, and, as truth is my pursuit, shall be glad to be informed. I have
seen few accounts of these whirl or eddy winds, and as little of the spouts;
and these, especially, lame and poor things to obtain any certainty by. If you
know any thing determinate that has been observed, I shall hope to hear
from you; as also of any mistake in my thoughts. I have nothing to object to
any other part of your suppositions: and as to that of the trade-winds, I
believe nobody can.
I am, &c.

P. S.. The figures in the Philosophical Transactions show, by several
circumstances, that they all descended, though the relators seemed to
think they took up water.

FOOTNOTES:

[3] Dr. Perkins. Editor.
[4] A Letter on Inoculation, which is transferred to a subsequent part of this
volume, that the papers on meteorological subjects may not be interrupted.
Editor.

DR. PERKINS OF BOSTON, TO BENJAMIN FRANKLIN, ESQ.
AT P H I L A D E L P H I A .

The same Subject continued.

Read at the Royal Society, June 24, 1756.

Boston, October 23, 1752.
Sir,
In the inclosed, you have all I have to say of that matter[5]. It proved
longer than I expected, so that I was forced to add a cover to it. I confess it
looks like a dispute; but that is quite contrary to my intentions.
The sincerity of friendship and esteem were my motives; nor do I doubt
your scrupling the goodness of the intention. However, I must confess I
cannot tell exactly how far I was acted by hopes of better information, in
discovering the whole foundation of my opinion, which, indeed, is but an
opinion, as I am very much at a loss about the validity of the reasons. I have
not been able to differ from you in sentiment concerning any thing else in
your Suppositions. In the present case I lie open to conviction, and shall be
the gainer when informed. If I am right, you will know that, without my
adding any more. Too much said on a merely speculative matter, is but a
robbery committed on practical knowledge. Perhaps I am too much pleased
with these dry notions: however, by this you will see that I think it
unreasonable to give you more trouble about them, than your leisure and
inclination may prompt you to.
I am, &c.

Since my last I considered, that, as I had begun with the reasons of my
dissatisfaction about the ascent of water in spouts, you would not be
unwilling to hear the whole I have to say, and then you will know what I
rely upon.
What occasioned my thinking all spouts descend, is, that I found some
did certainly do so. A difficulty appeared concerning the ascent of so heavy
a body as water, by any force I was apprised of, as probably sufficient. And,
above all, a view of Mr. Stuart's portraits of spouts, in the Philosophical
Transactions.
Some observations on these last will include the chief part of my
difficulties. Mr. Stuart has given us the figures of a number observed by
him in the Mediterranean: all with some particulars which make for my
opinion, if well drawn.
The great spattering, which relators mention in the water where the spout
descends, and which appears in all his draughts, I conceive to be occasioned
by drops descending very thick and large into the place.
On the place of this spattering, arises the appearance of a bush, into the
centre of which the spout comes down. This bush I take to be formed by a
spray, made by the force of these drops, which being uncommonly large,
and descending with unusual force by a stream of wind descending from the
cloud with them, increases the height of the spray: which wind being
repulsed by the surface of the waters rebounds and spreads; by the first
raising the spray higher than it otherwise would go; and by the last making
the top of the bush appear to bend outwards (i. e.) the cloud of spray is
forced off from the trunk of the spout, and falls backward.
The bush does the same where there is no appearance of a spout reaching
it; and is depressed in the middle, where the spout is expected. This, I
imagine, to be from numerous drops of the spout falling into it, together
with the wind I mentioned, by their descent, which beat back the rising
spray in the centre.
This circumstance, of the bush bending outwards at the top, seems not to
agree with what I call a direct whirlwind, but consistent with the reversed;
for a direct one would sweep the bush inwards; if, in that case, any thing of
a bush would appear.

The pillar of water, as they call it, from its likeness, I suppose to be only
the end of the spout immersed in the bush, a little blackened by the
additional cloud, and, perhaps, appears to the eye beyond its real bigness,
by a refraction in the bush, and which refraction may be the cause of the
appearance of separation, betwixt the part in the bush, and that above it. The
part in the bush is cylindrical, as it is above (i. e.) the bigness the same from
the top of the bush to the water. Instead of this shape, in case of a
whirlwind, it must have been pyramidical.
Another thing remarkable, is, the curve in some of them: this is easy to
conceive, in case of descending parcels of drops through various winds, at
least till the cloud condenses so fast as to come down, as it were, uno rivo.
But it is harder to me to conceive it in the ascent of water, that it should be
conveyed along, secure of not leaking or often dropping through the under
side, in the prone part: and, should the water be conveyed so swiftly, and
with such force, up into the cloud, as to prevent this, it would, by a natural
disposition to move on in a present direction, presently straiten the curve,
raising the shoulder very swiftly, till lost in the cloud.
Over every one of Stuart's figures, I see a cloud: I suppose his clouds
were first, and then the spout; I do not know whether it be so with all
spouts, but suppose it is. Now, if whirlwinds carried up the water, I should
expect them in fair weather, but not under a cloud; as is observable of
whirlwinds; they come in fair weather, not under the shade of a cloud, nor
in the night; since shade cools the air: but, on the contrary, violent winds
often descend from the clouds; strong gusts which occupy small spaces; and
from the higher regions, extensive hurricanes, &c.
Another thing is the appearance of the spout coming from the cloud. This
I cannot account for on the notion of a direct spout, but in the real
descending one, it is easy. I take it, that the cloud begins first of all to pour
out drops at that particular spot, or foramen; and, when that current of drops
increases, so as to force down wind and vapour, the spout becomes so far as
that goes opaque. I take it, that no clouds drop spouts, but such as make
very fast, and happen to condense in a particular spot, which perhaps is
coldest, and gives a determination downwards, so as to make a passage
through the subjacent atmosphere.

If spouts ascend, it is to carry up the warm rarefied air below, to let down
all and any that is colder above; and, if so, they must carry it through the
cloud they go into (for that is cold and dense, I imagine) perhaps far into the
higher region, making a wonderful appearance at a convenient distance to
observe it, by the swift rise of a body of vapour, above the region of the
clouds. But as this has never been observed in any age, if it be supposeable
that is all.
I cannot learn by mariners, that any wind blows towards a spout more
than any other way; but it blows towards a whirlwind, for a large distance
round.
I suppose there has been no instance of the water of a spout being salt,
when coming across any vessel at sea. I suppose too, that there have been
no salt rains; these would make the case clear.
I suppose it is from some unhappy effects of these dangerous creatures of
nature, that sailors have an universal dread on them of breaking in their
decks, should they come across them. I imagine spouts, in cold seasons, as
Gordon's in the Downs, prove the descent.
Query. Whether there is not always more or less cloud, first, where a
spout appears?
Whether they are not, generally, on the borders of trade-winds; and
whether this is for, or against me?
Whether there be any credible account of a whirlwind's carrying up all
the water in a pool, or small pond: as when shoal, and the banks low, a
strong gust might be supposed to blow it all out?
Whether a violent tornado, of a small extent, and other sudden and strong
gusts, be not winds from above, descending nearly perpendicular; and,
whether many that are called whirlwinds at sea, are any other than these;
and so might be called air-spouts, if they were objects of sight?
I overlooked, in its proper place, Stuart's No. 11, which is curious for its
inequalities, and, in particular, the approach to breaking, which, if it would
not be too tedious, I would have observed a little upon, in my own way, as,
I think, this would argue against the ascent, &c. but I must pass it, not only
for the reason mentioned, but want of room besides.

As to Mr. Stuart's ocular demonstration of the ascent in his great
perpendicular spout, the only one it appears in, I say, as to this, what I have
written supposes him mistaken, which, yet, I am far from asserting.
The force of an airy vortex, having less influence on the solid drops of
water, than on the interspersed cloudy vapours, makes the last whirl round
swifter, though it descend slower: and this might easily deceive, without
great care, the most unprejudiced person.

FOOTNOTE:

[5] Water-Spouts.

TO DOCTOR ——[6], OF BOSTON.

Water-Spouts and Whirlwinds compared.

Read at the Royal Society, June 24, 1756.

Philadelphia, Feb. 4, 1753.
Sir,
I ought to have written to you, long since, in answer to yours of October
16, concerning the water-spout; but business partly, and partly a desire of
procuring further information, by enquiry among my seafaring
acquaintance, induced me to postpone writing, from time to time, till I am
now almost ashamed to resume the subject, not knowing but you may have
forgot what has been said upon it.
Nothing certainly, can be more improving to a searcher into nature, than
objections judiciously made to his opinion, taken up, perhaps, too hastily:
for such objections oblige him to re-study the point, consider every
circumstance carefully, compare facts, make experiments, weigh arguments,
and be slow in drawing conclusions. And hence a sure advantage results; for
he either confirms a truth, before too slightly supported; or discovers an
error, and receives instruction from the objector.

In this view I consider the objections and remarks you sent me, and thank
you for them sincerely: but, how much soever my inclinations lead me to
philosophical enquiries, I am so engaged in business, public and private,
that those more pleasing pursuits are frequently interrupted, and the chain
of thought, necessary to be closely continued in such disquisitions, is so
broken and disjointed, that it is with difficulty I satisfy myself in any of
them: and I am now not much nearer a conclusion, in this matter of the
spout, than when I first read your letter.
Yet, hoping we may, in time, sift out the truth between us, I will send you
my present thoughts, with some observations on your reasons on the
accounts in the Transactions, and on other relations I have met with.
Perhaps, while I am writing, some new light may strike me, for I shall now
be obliged to consider the subject with a little more attention.
I agree with you, that, by means of a vacuum in a whirlwind, water
cannot be supposed to rise in large masses to the region of the clouds; for
the pressure of the surrounding atmosphere could not force it up in a
continued body, or column, to a much greater height, than thirty feet. But, if
there really is a vacuum in the centre, or near the axis of whirlwinds, then, I
think, water may rise in such vacuum to that height, or to a less height, as
the vacuum may be less perfect.
I had not read Stuart's account, in the Transactions, for many years,
before the receipt of your letter, and had quite forgot it; but now, on viewing
his draughts, and considering his descriptions, I think they seem to favour
my hypothesis; for he describes and draws columns of water, of various
heights, terminating abruptly at the top, exactly as water would do, when
forced up by the pressure of the atmosphere into an exhausted tube.
I must, however, no longer call it my hypothesis, since I find Stuart had
the same thought, though somewhat obscurely expressed, where he says,
"he imagines this phenomenon may be solved by suction (improperly so
called) or rather pulsion, as in the application of a cupping glass to the
flesh, the air being first voided by the kindled flax." In my paper, I
supposed a whirlwind and a spout to be the same thing, and to proceed from
the same cause; the only difference between them being, that the one passes
over land, the other over water, I find, also, in the Transactions, that M. de
la Pryme was of the same opinion; for he there describes two spouts, as he

calls them, which were seen at different times, at Hatfield, in Yorkshire,
whose appearances in the air were the same with those of the spouts at sea,
and effects the same with those of real whirlwinds.
Whirlwinds have generally a progressive, as well as a circular motion; so
had what is called the spout, at Topsham—(See the account of it in the
Transactions) which also appears, by its effects described, to have been a
real whirlwind. Water-spouts have, also, a progressive motion; this is
sometimes greater, and sometimes less; in some violent, in others barely
perceivable. The whirlwind at Warrington continued long in Acrement-
Close.
Whirlwinds generally arise after calms and great heats: the same is
observed of water-spouts, which are, therefore, most frequent in the warm
latitudes. The spout that happened in cold weather, in the Downs, described
by Mr. Gordon in the Transactions, was, for that reason, thought
extraordinary; but he remarks withal, that the weather, though cold when
the spout appeared, was soon after much colder; as we find it, commonly,
less warm after a whirlwind.
You agree, that the wind blows every way towards a whirlwind, from a
large space round. An intelligent whaleman of Nantucket, informed me that
three of their vessels, which were out in search of whales, happening to be
becalmed, lay in sight of each other, at about a league distance, if I
remember right, nearly forming a triangle: after some time, a water-spout
appeared near the middle of the triangle, when a brisk breeze of wind
sprung up, and every vessel made sail; and then it appeared to them all, by
the setting of the sails, and the course each vessel stood, that the spout was
to the leeward of every one of them; and they all declared it to have been
so, when they happened afterwards in company, and came to confer about
it. So that in this particular likewise, whirlwinds and water-spouts agree.
But, if that which appears a water-spout at sea, does sometimes, in its
progressive motion, meet with and pass over land, and there produce all the
phenomena and effects of a whirlwind, it should thence seem still more
evident, that a whirlwind and a spout are the same. I send you, herewith, a
letter from an ingenious physician of my acquaintance, which gives one
instance of this, that fell within his observation.

A fluid, moving from all points horizontally, towards a centre, must, at
that centre, either ascend or descend. Water being in a tub, if a hole be
opened in the middle of the bottom, will flow from all sides to the centre,
and there descend in a whirl. But, air flowing on and near the surface of
land or water, from all sides, towards a centre, must, at that centre ascend;
the land or water hindering its descent.
If these concentring currents of air be in the upper region, they may,
indeed, descend in the spout or whirlwind; but then, when the united current
reached the earth or water, it would spread, and, probably, blow every way
from the centre. There may be whirlwinds of both kinds, but from the
commonly observed effects, I suspect the rising one to be the most
common: when the upper air descends, it is, perhaps, in a greater body,
extending wider, as in our thunder-gusts, and without much whirling; and,
when air descends in a spout, or whirlwind, I should rather expect it would
press the roof of a house inwards, or force in the tiles, shingles, or thatch,
force a boat down into the water, or a piece of timber into the earth, than
that it would lift them up, and carry them away.
It has so happened, that I have not met with any accounts of spouts, that
certainly descended; I suspect they are not frequent. Please to communicate
those you mention. The apparent dropping of a pipe from the clouds
towards the earth or sea, I will endeavour to explain hereafter.
The augmentation of the cloud, which, as I am informed, is generally, if
not always the case, during a spout, seems to shew an ascent, rather than a
descent of the matter of which such cloud is composed; for a descending
spout, one would expect, should diminish a cloud. I own, however, that cold
air descending, may, by condensing the vapours in a lower region, form and
increase clouds; which, I think, is generally the case in our common
thunder-gusts, and, therefore, do not lay great stress on this argument.
Whirlwinds and spouts, are not always, though most commonly, in the
day time. The terrible whirlwind which damaged a great part of Rome, June
11, 1749, happened in the night of that day. The same was supposed to have
been first a spout, for it is said to be beyond doubt, that it gathered in the
neighbouring sea, as it could be tracked from Ostia to Rome. I find this in
Pere Boschovich's account of it, as abridged in the Monthly Review for
December 1750. In that account, the whirlwind is said to have appeared as a

very black, long, and lofty cloud, discoverable, notwithstanding the
darkness of the night, by its continually lightning or emitting flashes on all
sides, pushing along with a surprising swiftness, and within three or four
feet of the ground. Its general effects on houses, were stripping off the
roofs, blowing away chimneys, breaking doors and windows, forcing up the
floors, and unpaving the rooms (some of these effects seem to agree well
with a supposed vacuum in the centre of the whirlwind) and the very rafters
of the houses were broken and dispersed, and even hurled against houses at
a considerable distance, &c.
It seems, by an expression of Pere Boschovich's, as if the wind blew from
all sides towards the whirlwind; for, having carefully observed its effects,
he concludes of all whirlwinds, "that their motion is circular, and their
action attractive."
He observes, on a number of histories of whirlwinds, &c. "that a
common effect of them is, to carry up into the air, tiles, stones, and animals
themselves, which happen to be in their course, and all kinds of bodies
unexceptionably, throwing them to a considerable distance, with great
impetuosity."
Such effects seem to shew a rising current of air.
I will endeavour to explain my conceptions of this matter by figures,
representing a plan and an elevation of a spout or whirlwind.
I would only first beg to be allowed two or three positions, mentioned in
my former paper.
1. That the lower region of air is often more heated, and so more rarefied,
than the upper; consequently, specifically lighter. The coldness of the upper
region is manifested by the hail which sometimes falls from it in a hot day.
2. That heated air may be very moist, and yet the moisture so equally
diffus'd and rarefied, as not to be visible, till colder air mixes with it, when
it condenses, and becomes visible. Thus our breath, invisible in summer,
becomes visible in winter.
Now let us suppose a tract of land, or sea, of perhaps sixty miles square,
unscreened by clouds, and unfanned by winds, during great part of a
summer's day, or, it may be, for several days successively, till it is violently
heated, together with the lower region of air in contact with it, so that the

said lower air becomes specifically lighter than the superincumbent higher
region of the atmosphere, in which the clouds commonly float: let us
suppose, also, that the air surrounding this tract has not been so much
heated during those days, and, therefore, remains heavier. The consequence
of this should be, as I conceive, that the heated lighter air, being pressed on
all sides, must ascend, and the heavier descend; and, as this rising cannot be
in all parts, or the whole area of the tract at once, for that would leave too
extensive a vacuum, the rising will begin precisely in that column that
happens to be the lightest, or most rarefied; and the warm air will flow
horizontally from all points to this column, where the several currents
meeting, and joining to rise, a whirl is naturally formed, in the same manner
as a whirl is formed in the tub of water, by the descending fluid flowing
from all sides of the tub, to the hole in the centre.
And, as the several currents arrive at this central rising column, with a
considerable degree of horizontal motion, they cannot suddenly change it to
a vertical motion; therefore as they gradually, in approaching the whirl,
decline from right to curve or circular lines, so, having joined the whirl,
they ascend by a spiral motion, in the same manner as the water descends
spirally through the hole in the tub before-mentioned.
Lastly, as the lower air, and nearest the surface, is most rarefied by the
heat of the sun, that air is most acted on by the pressure of the surrounding
cold and heavy air, which is to take its place; consequently, its motion
towards the whirl is swiftest, and so the force of the lower part of the whirl,
or trump, strongest, and the centrifugal force of its particles greatest; and
hence the vacuum round the axis of the whirl should be greatest near the
earth or sea, and be gradually diminished as it approaches the region of the
clouds, till it ends in a point, as at P in Fig. II. Plate V. forming a long and
sharp cone.
In Fig. I. which is a plan or ground-plat of a whirlwind, the circle V.
represents the central vacuum.
Between a a a a and b b b b I suppose a body of air, condensed strongly
by the pressure of the currents moving towards it, from all sides without,
and by its centrifugal force from within, moving round with prodigious
swiftness, (having, as it were, the momenta of all the currents ——> ——>

——> ——> united in itself) and with a power equal to its swiftness and
density.

Plate V. Vol. II. page 26.

View larger image here
Published as the Act directs, April 1, 1806, by Longman, Hurst, Rees & Orme, Paternoster Row.

It is this whirling body of air between a a a a and b b b b that rises
spirally; by its force it tears buildings to pieces, twists up great trees by the

roots, &c. and, by its spiral motion, raises the fragments so high, till the
pressure of the surrounding and approaching currents diminishing, can no
longer confine them to the circle, or their own centrifugal force encreasing,
grows too strong for such pressure, when they fly off in tangent lines, as
stones out of a sling, and fall on all sides, and at great distances.
If it happens at sea, the water under and between a a a a and b b b b will
be violently agitated and driven about, and parts of it raised with the spiral
current, and thrown about so as to form a bush-like appearance.
This circle is of various diameters, sometimes very large.
If the vacuum passes over water, the water may rise in it in a body, or
column, to near the height of thirty-two feet.
If it passes over houses, it may burst their windows or walls outwards,
pluck off the roofs, and pluck up the floors, by the sudden rarefaction of the
air contained within such buildings; the outward pressure of the atmosphere
being suddenly taken off: so the stopped bottle of air bursts under the
exhausted receiver of the air-pump.
Fig. II. is to represent the elevation of a water-spout, wherein I suppose P
P P to be the cone, at first a vacuum, till W W, the rising column of water,
has filled so much of it. S S S S, the spiral whirl of air, surrounding the
vacuum, and continued higher in a close column after the vacuum ends in
the point P, till it reaches the cool region of the air. B B, the bush described
by Stuart, surrounding the foot of the column of water.
Now, I suppose this whirl of air will, at first, be as invisible as the air
itself, though reaching, in reality, from the water, to the region of cool air, in
which our low summer thunder-clouds commonly float; but presently it will
become visible at its extremities. At its lower end, by the agitation of the
water, under the whirling part of the circle, between P and S forming
Stuart's bush, and by the swelling and rising of the water, in the beginning
vacuum, which is, at first, a small, low, broad cone, whose top gradually
rises and sharpens, as the force of the whirl encreases. At its upper end it
becomes visible, by the warm air brought up to the cooler region, where its
moisture begins to be condensed into thick vapour, by the cold, and is seen
first at A, the highest part, which being now cooled, condenses what rises
next at B, which condenses that at C, and that condenses what is rising at D,

the cold operating by the contact of the vapours faster in a right line
downwards, than the vapours themselves can climb in a spiral line upwards;
they climb, however, and as by continual addition they grow denser, and,
consequently, their centrifugal force greater, and being risen above the
concentrating currents that compose the whirl, fly off, spread, and form a
cloud.
It seems easy to conceive, how, by this successive condensation from
above, the spout appears to drop or descend from the cloud, though the
materials of which it is composed are all the while ascending.
The condensation of the moisture, contained in so great a quantity of
warm air as may be supposed to rise in a short time in this prodigiously
rapid whirl, is, perhaps, sufficient to form a great extent of cloud, though
the spout should be over land, as those at Hatfield; and if the land happens
not to be very dusty, perhaps the lower part of the spout will scarce become
visible at all; though the upper, or what is commonly called the descending
part, be very distinctly seen.
The same may happen at sea, in case the whirl is not violent enough to
make a high vacuum, and raise the column, &c. In such case, the upper part
A B C D only will be visible, and the bush, perhaps, below.
But if the whirl be strong, and there be much dust on the land, and the
column W W be raised from the water, then the lower part becomes visible,
and sometimes even united to the upper part. For the dust may be carried up
in the spiral whirl, till it reach the region where the vapour is condensed,
and rise with that even to the clouds: and the friction of the whirling air, on
the sides of the column W W, may detach great quantities of its water, break
it into drops, and carry them up in the spiral whirl mixed with the air; the
heavier drops may, indeed, fly off, and fall, in a shower, round the spout;
but much of it will be broken into vapour, yet visible; and thus, in both
cases, by dust at land, and, by water at sea, the whole tube may be darkened
and rendered visible.
As the whirl weakens, the tube may (in appearance) separate in the
middle; the column of water subsiding, and the superior condensed part
drawing up to the cloud. Yet still the tube, or whirl of air, may remain
entire, the middle only becoming invisible, as not containing visible matter.

Dr. Stuart says, "It was observable of all the spouts he saw, but more
perceptible of the great one; that; towards the end, it began to appear like a
hollow canal, only black in the borders, but white in the middle; and though
at first it was altogether black and opaque, yet, now, one could very
distinctly perceive the sea-water to fly up along the middle of this canal, as
smoak up a chimney."
And Dr. Mather, describing a whirlwind, says, "a thick dark small cloud
arose, with a pillar of light in it, of about eight or ten feet diameter, and
passed along the ground in a tract not wider than a street, horribly tearing
up trees by the roots, blowing them up in the air like feathers, and throwing
up stones of great weight to a considerable height in the air, &c."
These accounts, the one of water-
spouts, the other of a whirlwind,
seem, in this particular, to agree;
what one gentleman describes as a
tube, black in the borders, and
white in the middle, the other calls
a black cloud, with a pillar of light
in it; the latter expression has only a
little more of the marvellous, but
the thing is the same; and it seems
not very difficult to understand.
When Dr. Stuart's spouts were full
charged, that is, when the whirling
pipe of air was filled between a a a
a and b b b b, Fig. I., with quantities of drops, and vapour torn off from the
column W W, Fig. II., the whole was rendered so dark, as that it could not
be seen thro', nor the spiral ascending motion discovered; but when the
quantity ascending lessened, the pipe became more transparent, and the
ascending motion visible. For, by inspection of the figure in the opposite
page, representing a section of our spout, with the vacuum in the middle, it
is plain that if we look at such a hollow pipe in the direction of the arrows,
and suppose opaque particles to be equally mixed in the space between the
two circular lines, both the part between the arrows a and b, and that
between the arrows c and d, will appear much darker than that between b
and c, as there must be many more of those opaque particles in the line of

vision across the sides, than across the middle. It is thus that a hair in a
microscope evidently appears to be a pipe, the sides shewing darker than
the middle. Dr. Mather's whirl was probably filled with dust, the sides were
very dark, but the vacuum within rendering the middle more transparent, he
calls it a pillar of light.
It was in this more transparent part, between b and c, that Stuart could
see the spiral motion of the vapours, whose lines on the nearest and farthest
side of the transparent part crossing each other, represented smoak
ascending in a chimney; for the quantity being still too great in the line of
sight through the sides of the tube, the motion could not be discovered
there, and so they represented the solid sides of the chimney.
When the vapours reach in the pipe from the clouds near to the earth, it is
no wonder now to those who understand electricity, that flashes of lightning
should descend by the spout, as in that of Rome.
But you object, if water may be thus carried into the clouds, why have we
not salt rains? The objection is strong and reasonable, and I know not
whether I can answer it to your satisfaction. I never heard but of one salt
rain, and that was where a spout passed pretty near a ship, so I suppose it to
be only the drops thrown off from the spout, by the centrifugal force (as the
birds were at Hatfield) when they had been carried so high as to be above,
or to be too strongly centrifugal for, the pressure of the concurring winds
surrounding it: and, indeed, I believe there can be no other kind of salt rain;
for it has pleased the goodness of God so to order it, that the particles of air
will not attract the particles of salt, though they strongly attract water.
Hence, though all metals, even gold, may be united with air, and rendered
volatile, salt remains fixt in the fire, and no heat can force it up to any
considerable height, or oblige the air to hold it. Hence, when salt rises, as it
will a little way, into air with water, there is instantly a separation made; the
particles of water adhere to the air, and the particles of salt fall down again,
as if repelled and forced off from the water by some power in the air; or, as
some metals, dissolved in a proper menstruum, will quit the solvent when
other matter approaches, and adhere to that, so the water quits the salt, and
embraces the air; but air will not embrace the salt, and quit the water,
otherwise our rains would indeed be salt, and every tree and plant on the
face of the earth be destroyed, with all the animals that depend on them for

subsistence.——He who hath proportioned and given proper qualities to all
things, was not unmindful of this. Let us adore Him with praise and
thanksgiving! By some accounts of seamen, it seems the column of water
W W, sometimes falls suddenly; and if it be, as some say, fifteen or twenty
yards diameter, it must fall with great force, and they may well fear for their
ships. By one account, in the Transactions, of a spout that fell at Colne in
Lancashire, one would think the column is sometimes lifted off from the
water, and carried over land, and there let fall in a body; but this, I suppose,
happens rarely.
Stuart describes his spouts as appearing no bigger than a mast, and
sometimes less; but they were seen at a league and a half distance.
I think I formerly read in Dampier, or some other voyager, that a spout, in
its progressive motion, went over a ship becalmed, on the coast of Guinea,
and first threw her down on one side, carrying away her foremast, then
suddenly whipped her up, and threw her down on the other side, carrying
away her mizen-mast, and the whole was over in an instant. I suppose the
first mischief was done by the fore-side of the whirl, the latter by the
hinder-side, their motion being contrary.
I suppose a whirlwind, or spout, may be stationary, when the concurring
winds are equal; but if unequal, the whirl acquires a progressive motion, in
the direction of the strongest pressure.
When the wind that gives the progressive motion becomes stronger
below than above, or above than below, the spout will be bent, and, the
cause ceasing, straiten again.
Your queries, towards the end of your paper, appear judicious, and worth
considering. At present I am not furnished with facts sufficient to make any
pertinent answer to them; and this paper has already a sufficient quantity of
conjecture.
Your manner of accommodating the accounts to your hypothesis of
descending spouts, is, I own, ingenious, and perhaps that hypothesis may be
true. I will consider it farther, but, as yet, I am not satisfied with it, though
hereafter I may be.
Here you have my method of accounting for the principal phenomena,
which I submit to your candid examination.

And as I now seem to have almost written a book, instead of a letter, you
will think it high time I should conclude; which I beg leave to do, with
assuring you, that
I am, Sir, &c.
B. FRANKLIN.

FOOTNOTE:

[6] Perkins. Editor.

D O C T O R M — — [ 7 ] , T O B E N J A M I N F R A N K L I N , E S Q . AT
PHILADELPHIA.

Description of a Water-Spout at Antigua.

Read at the Royal Society, June 24, 1756.

New-Brunswick, November 11, 1752.
Sir,
I am favoured with your letter of the 2d instant, and shall, with pleasure,
comply with your request, in describing (as well as my memory serves me)
the water-spout I saw at Antigua; and shall think this, or any other service I
can do, well repaid, if it contributes to your satisfaction in so curious a
disquisition.
I had often seen water-spouts at a distance, and heard many strange
stories of them, but never knew any thing satisfactory of their nature or
cause, until that which I saw at Antigua; which convinced me that a water-
spout is a whirlwind, which becomes visible in all its dimensions by the
water it carries up with it.
There appeared, not far from the mouth of the harbour of St. John's, two
or three water-spouts, one of which took its course up the harbour. Its
progressive motion was slow and unequal, not in a strait line, but, as it
were, by jerks or starts. When just by the wharf, I stood about one hundred
yards from it. There appeared in the water a circle of about twenty yards
diameter, which, to me, had a dreadful, though pleasing appearance. The
water in this circle was violently agitated, being whisked about, and carried
up into the air with great rapidity and noise, and reflected a lustre, as if the
sun shined bright on that spot, which was more conspicuous, as there
appeared a dark circle around it. When it made the shore, it carried up with
the same violence shingles, staves[8], large pieces of the roofs of houses,
&c. and one small wooden house it lifted entire from the foundation on
which it stood, and carried it to the distance of fourteen feet, where it settled
without breaking or oversetting; and, what is remarkable, though the
whirlwind moved from west to east, the house moved from east to west.

Two or three negroes and a white woman, were killed by the fall of timber,
which it carried up into the air and dropped again. After passing through the
town, I believe it was soon dissipated; for, except tearing a large limb from
a tree, and part of the cover of a sugar-work near the town, I do not
remember any farther damage done by it. I conclude, wishing you success
in your enquiry,
And am, &c.
W. M.

FOOTNOTES:

[7] Dr. Mercer. Editor.
[8] I suppose shingles, staves, timber, and other lumber, might be lying in
quantities on the wharf, for sale, as brought from the northern colonies. B. F.

DOCTOR ——[9], OF BOSTON, TO BENJAMIN FRANKLIN, ESQ.
AT P H I L A D E L P H I A .

Shooting Stars.

Read at the Royal Society, July 8, 1756.

Boston, May 14, 1753.
Sir,
I received your letter of April last, and thank you for it. Several things in
it make me at a loss which side the truth lies on, and determine me to wait
for farther evidence.
As to shooting-stars, as they are called, I know very little, and hardly
know what to say. I imagine them to be passes of electric fire from place to
place in the atmosphere, perhaps occasioned by accidental pressures of a
non-electric circumambient fluid, and so by propulsion, or allicited by the
circumstance of a distant quantity minus electrified, which it shoots to
supply, and becomes apparent by its contracted passage through a non-
electric medium. Electric fire in our globe is always in action, sometimes
ascending, descending, or passing from region to region. I suppose it avoids
too dry air, and therefore we never see these shoots ascend. It always has
freedom enough to pass down unobserved, but, I imagine, not always so, to
pass to distant climes and meridians less stored with it.
The shoots are sometimes all one way, which, in the last case, they
should be.
Possibly there may be collections of particles in our atmosphere, which
gradually form, by attraction, either similar ones per se, or dissimilar
particles, by the intervention of others. But then, whether they shoot or
explode of themselves, or by the approach of some suitable foreign
collection, accidentally brought near by the usual commotions and
interchanges of our atmosphere, especially when the higher and lower
regions intermix, before change of winds and weather, I leave.

I believe I have now said enough of what I know nothing about. If it
should serve for your amusement, or any way oblige you, it is all I aim at,
and shall, at your desire, be always ready to say what I think, as I am sure
of your candour.
I am, &c.

FOOTNOTE:

[9] Dr. Perkins. Editor.

A subsequent Paper from the same.
Water-Spouts and Whirlwinds.

Read at the Royal Society, July 8, 1756.

Spouts have been generally believed ascents of water from below, to the
region of the clouds, and whirlwinds the means of conveyance. The world
has been very well satisfied with these opinions, and prejudiced with
respect to any observations about them. Men of learning and capacity have
had many opportunities in passing those regions where these phenomena
were most frequent, but seem industriously to have declined any notice of
them, unless to escape danger, as a matter of mere impertinence in a case so
clear and certain as their nature and manner of operation are taken to be.
Hence it has been very difficult to get any tolerable accounts of them. None
but those they fell near can inform us any thing to be depended on; three or
four such instances follow, where the vessels were so near, that their crews
could not avoid knowing something remarkable with respect to the matters
in question.
Capt. John Wakefield, junior, passing the Straits of Gibraltar, had one fall
by the side of his ship; it came down of a sudden, as they think, and all
agree the descent was certain.

Captain Langstaff, on a voyage to the West Indies, had one come across
the stern of his vessel, and passed away from him. The water came down in
such quantity that the present Captain Melling, who was then a common
sailor at helm, says it almost drowned him, running into his mouth, nose,
ears, &c. and adds, that it tasted perfectly fresh.
One passed by the side of Captain Howland's ship, so near that it
appeared pretty plain that the water descended from first to last.
Mr. Robert Spring was so near one in the Straits of Malacca, that he
could perceive it to be a small very thick rain.
All these assure me, that there was no wind drawing towards them, nor
have I found any others that have observed such a wind.
It seems plain, by these few instances, that whirlwinds do not always
attend spouts; and that the water really descends in some of them. But the
following consideration, in confirmation of this opinion, may, perhaps,
render it probable that all the spouts are descents.
It seems unlikely that there should be two sorts of spouts, one ascending
and the other descending.
It has not yet been proved that any one spout ever ascended. A specious
appearance is all that can be produced in favour of this; and those who have
been most positive about it, were at more than a league's distance when they
observed, as Stuart and others, if I am not mistaken. However, I believe it
impossible to be certain whether water ascends or descends at half the
distance.
It may not be amiss to consider the places where they happen most.
These are such as are liable to calms from departing winds on both sides, as
on the borders of the equinoctial trade, calms on the coast of Guinea, in the
Straits of Malacca, &c. places where the under region of the atmosphere is
drawn off horizontally. I think they do not come where the calms are
without departing winds; and I take the reason to be, that such places, and
places where winds blow towards one another, are liable to whirlwinds, or
other ascents of the lower region, which I suppose contrary to spouts. But
the former are liable to descents, which I take to be necessary to their
production. Agreeable to this, it seems reasonable to believe, that any
Mediterranean sea should be more subject to spouts than others. The sea

usually so called is so. The Straits of Malacca is. Some large gulphs may
probably be so, in suitable latitudes; so the Red Sea, &c. and all for this
reason, that the heated lands on each side draw off the under region of the
air, and make the upper descend, whence sudden and wonderful
condensations may take place, and make these descents.
It seems to me, that the manner of their appearance and procedure, favour
the notion of a descent.
More or less of a cloud, as I am informed, always appears over the place
first; then a spattering on the surface of the water below; and when this is
advanced to a considerable degree, the spout emerges from the cloud, and
descends, and that, if the causes are sufficient, down to the places of
spattering, with a roaring in proportion to the quantity of the discharge; then
it abates, or stops, sometimes more gradually, sometimes more suddenly.
I must observe a few things on these particulars, to shew how I think they
agree with my hypothesis.
The preceding cloud over the place shews condensation, and,
consequently, tendency downwards, which therefore must naturally prevent
any ascent. Besides that, so far as I can learn, a whirlwind never comes
under a cloud, but in a clear sky.
The spattering may be easily conceived to be caused by a stream of
drops, falling with great force on the place, imagining the spout to begin so,
when a sudden and great condensation happens in a contracted space, as the
Ox-Eye on the coast of Guinea.
The spout appearing to descend from the cloud seems to be, by the
stream of nearly contiguous drops bringing the air into consent, so as to
carry down a quantity of the vapour of the cloud; and the pointed
appearance it makes may be from the descending course being swiftest in
the middle, or centre of the spout: this naturally drawing the outer parts
inward, and the centre to a point; and that will appear foremost that moves
swiftest. The phenomenon of retiring and advancing, I think may be
accounted for, by supposing the progressive motion to exceed or not equal
the consumption of the vapour by condensation. Or more plainly thus: the
descending vapour which forms the apparent spout, if it be slow in its
progress downwards, is condensed as fast as it advances, and so appears at a

stand; when it is condensed faster than it advances, it appears to retire; and
vice versa.
Its duration, and manner of ending, are as the causes, and may vary by
several accidents.
The cloud itself may be so circumstanced as to stop it; as when,
extending wide, it weighs down at a distance round about, while a small
circle at the spout being exonerated by the discharge ascends and shuts up
the passage. A new determination of wind may, perhaps, stop it too. Places
liable to these appearances are very liable to frequent and sudden alterations
of it.
Such accidents as a clap of thunder, firing cannon, &c. may stop them,
and the reason may be, that any shock of this kind may occasion the
particles that are near cohering, immediately to do so; and then the whole,
thus condensed, falls at once (which is what I suppose is vulgarly called the
breaking of the spout) and in the interval, between this period and that of
the next set of particles being ready to unite, the spout shuts up. So that if
this reasoning is just, these phenomena agree with my hypothesis.
The usual temper of the air, at the time of their appearance, if I have a
right information, is for me to; it being then pretty cool for the season and
climate; and this is worth remark, because cool air is weighty, and will not
ascend; besides, when the air grows cool, it shews that the upper region
descends, and conveys this temper down; and when the tempers are equal,
no whirlwind can take place. But spouts have been known, when the lower
region has been really cold. Gordon's spout in the Downs is an instance of
this—(Vide Philosophical Transactions)—where the upper region was
probably not at all cooler, if so cold as the lower: it was a cold day in the
month of March, hail followed, but not snow, and it is observable, that not
so much as hail follows or accompanies them in moderate seasons or
climes, when and where they are most frequent. However, it is not
improbable, that just about the place of descent may be cooler than the
neighbouring parts, and so favour the wonderful celerity of condensation.
But, after all, should we allow the under region to be ever so much the
hottest, and a whirlwind to take place in it: suppose then the sea-water to
ascend, it would certainly cool the spout, and then, query, whether it would
not very much, if not wholly, obstruct its progress.

It commonly rains when spouts disappear, if it did not before, which it
frequently does not, by the best accounts I have had; but the cloud
encreases much faster after they disappear, and it soon rains. The first
shews the spout to be a contracted rain, instead of the diffused one that
follows; and the latter that the cloud was not formed by ascending water, for
then it would have ceased growing when the spout vanished.
However, it seems that spouts have sometimes appeared after it began to
rain; but this is one way a proof of my hypothesis, viz. as whirlwinds do not
come under a cloud.
I forgot to mention, that the increase of cloud, while the spout subsists, is
no argument of an ascent of water, by the spout. Since thunder-clouds
sometimes encrease greatly while it rains very hard.
Divers effects of spouts seem not so well accounted for any other way as
by descent.
The bush round the feet of them seems to be a great spray of water made
by the violence of descent, like that in great falls of water from high
precipices.
The great roar, like some vast inland falls, is so different from the roar of
whirlwinds, by all acounts, as to be no ways compatible.
The throwing things from it with great force, instead of carrying them up
into the air, is another difference.
There seems some probability that the sailors traditionary belief, that
spouts may break in their decks, and so destroy vessels, might originate
from some facts of that sort in former times. This danger is apparent on my
hypothesis, but it seems not so on the other: and my reason for it is, that the
whole column of a spout from the sea to the clouds, cannot, in a natural
way, even upon the largest supposition, support more than about three feet
water, and from truly supposeable causes, not above one foot, as may
appear more plainly by and by. Supposing now the largest of these
quantities to rise, it must be disseminated into drops, from the surface of the
sea to the region of the clouds, or higher; for this reason it is quite unlikely
to be collected into masses, or a body, upon its falling; but would descend
in progression according to the several degrees of altitude the different
portions had arrived at when it received this new determination.

Now that there cannot more rise upon the common hypothesis than I
have mentioned, may appear probable, if we attend to the only efficient
cause in supposed ascending spouts, viz. whirlwinds.
We know that the rarefaction of the lower, and the condensation of the
upper region of air, are the only natural causes of whirlwinds. Let us then
suppose the former as hot as their greatest summer heat in England, and the
latter as cold as the extent of their winter. These extremes have been found
there to alter the weight of the air one-tenth, which is equal to a little more
than three feet water. Were this case possible, and a whirlwind take place in
it, it might act with a force equal to the mentioned difference. But as this is
the whole strength, so much water could not rise; therefore to allow it due
motion upwards, we must abate, at least, one-fourth part, perhaps more, to
give it such a swift ascension as some think usual. But here several
difficulties occur, at least they are so to me. As, whether this quantity would
render the spout opaque? since it is plain that in drops it could not do so.
How, or by what means it may be reduced small enough? or, if the water be
not reduced into vapour, what will suspend it in the region of the clouds
when exonerated there? And, if vapourized while ascending, how can it be
dangerous by what they call the breaking? For it is difficult to conceive how
a condensative power should instantaneously take place of a rarefying and
disseminating one.
The sudden fall of the spout, or rather, the sudden ceasing of it, I
accounted for, in my way, before. But it seems necessary to mention
something I then forgot. Should it be said to do so (i. e.) to fall, because all
the lower rarefied air is ascended, whence the whirlwind must cease, and its
burden drop; I cannot agree to this, unless the air be observed on a sudden
to have grown much colder, which I cannot learn has been the case. Or
should it be supposed that the spout was, on a sudden, obstructed at the top,
and this the cause of the fall, however plausible this might appear, yet no
more water would fall than what was at the same time contained in the
column, which is often, by many and satisfactory accounts to me, again far
from being the case.
We are, I think, sufficiently assured, that not only tons, but scores or
hundreds of tons descend in one spout. Scores of tons more than can be
contained in the trunk of it, should we suppose water to ascend.

But, after all, it does not appear that the above-mentioned different
degrees of heat and cold concur in any region where spouts usually happen,
nor, indeed, in any other.

Observations on the Meteorological Paper; by a Gentleman in Connecticut.

Read at the Royal Society, Nov. 4, 1756.

"Air and water mutually attract each other, (saith Mr. F.) hence water will
dissolve in air, as salt in water." I think that he hath demonstrated, that the
supporting of salt in water is not owing to its superficies being increased,
because "the specific gravity of salt is not altered by dividing of it, any
more than that of lead, sixteen bullets of which, of an ounce each, weigh as
much in water as one of a pound." But yet, when this came to be applied to
the supporting of water in air, I found an objection rising in my mind.
In the first place, I have always been loth to seek for any new hypothesis,
or particular law of nature, to account for any thing that may be accounted
for from the known, general, and universal law of nature; it being an
argument of the infinite wisdom of the author of the world, to effect so
many things by one general law. Now I had thought that the rising and
support of water in air, might be accounted for from the general law of
gravitation, by only supposing the spaces occupied by the same quantity of
water increased.
And, with respect to the lead, I queried thus in my own mind; whether if
the superficies of a bullet of lead should be increased four or five fold by an
internal vacuity, it would weigh the same in water as before. I mean, if a
pound of lead should be formed into a hollow globe, empty within, whose
superficies should be four or five times as big as that of the same lead when
a solid lump, it would weigh as much in water as before. I supposed it
would not. If this concavity was filled with water, perhaps it might; if with
air, it would weigh at least as much less, as this difference between the
weight of that included air, and that of water.
Now although this would do nothing to account for the dissolution of salt
in water, the smallest lumps of salt being no more hollow spheres, or any

thing of the like nature than the greatest; yet, perhaps, it might account for
water's rising and being supported in air. For you know that such hollow
globules, or bubbles, abound upon the surface of the water, which even by
the breath of our mouths, we can cause to quit the water, and rise in the air.
These bubbles I used to suppose to be coats of water, containing within
them air rarefied and expanded with fire, and that, therefore, the more
friction and dashing there is upon the surface of the waters, and the more
heat and fire, the more they abound.
And I used to think, that although water be specifically heavier than air,
yet such a bubble, filled only with fire and very rarefied air, may be lighter
than a quantity of common air, of the same cubical dimensions, and,
therefore, ascend; for the rarefied air inclosed, may more fall short of the
same bulk of common air, in weight, than the watery coat exceeds a like
bulk of common air in gravity.
This was the objection in my mind, though, I must confess, I know not
how to account for the watery coat's encompassing the air, as above-
mentioned, without allowing the attraction between air and water, which the
gentleman supposes; so that I do not know but that this objection, examined
by that sagacious genius, will be an additional confirmation of the
hypothesis.
The gentleman observes, "that a certain quantity of moisture should be
every moment discharged and taken away from the lungs; and hence
accounts for the suffocating nature of snuffs of candles, as impregnating the
air with grease, between which and water there is a natural repellency; and
of air that hath been frequently breathed in, which is overloaded with water,
and, for that reason, can take no more air. Perhaps the same observation will
account for the suffocating nature of damps in wells."
But then if the air can support and take off but such a proportion of water,
and it is necessary that water be so taken off from the lungs, I queried with
myself how it is we can breathe in an air full of vapours, so full as that they
continually precipitated. Do not we see the air overloaded, and casting forth
water plentifully when there is no suffocation?
The gentleman again observes, "That the air under the equator, and
between the tropics, being constantly heated and rarefied by the sun, rises;

its place is supplied by air from northern and southern latitudes, which,
coming from parts where the air and earth had less motion, and not
suddenly acquiring the quicker motion of the equatorial earth, appears an
east wind blowing westward; the earth moving from west to east, and
slipping under the air."
In reading this, two objections occurred to my mind:
First, that it is said, the trade-wind doth not blow in the forenoon, but
only in the afternoon.
Secondly, that either the motion of the northern and southern air towards
the equator is so slow, as to acquire almost the same motion as the
equatorial air when it arrives there, so that there will be no sensible
difference; or else the motion of the northern and southern air towards the
equator, is quicker, and must be sensible; and then the trade-wind must
appear either as a south-east or north-east wind: south of the equator, a
south-east wind; north of the equator, a north-east. For the apparent wind
must be compounded of this motion from north to south, or vice versa; and
of the difference between its motion from west to east, and that of the
equatorial air.

Observations in Answer to the foregoing, by B. Franklin.

Read at the Royal Society, Nov. 4, 1756.

1st. The supposing a mutual attraction between the particles of water and
air is not introducing a new law of nature; such attractions taking place in
many other known instances.
2dly. Water is specifically 850 times heavier than air. To render a bubble
of water, then, specifically lighter than air, it seems to me that it must take
up more than 850 times the space it did before it formed the bubble; and
within the bubble should be either a vacuum or air rarefied more than 850
times. If a vacuum, would not the bubble be immediately crushed by the
weight of the atmosphere? And no heat, we know of, will rarefy air any
thing near so much; much less the common heat of the sun, or that of
friction by the dashing on the surface of the water. Besides, water agitated

ever so violently produces no heat, as has been found by accurate
experiments.
3dly. A hollow sphere of lead has a firmness and consistency in it, that a
hollow sphere or bubble of fluid unfrozen water cannot be supposed to
have. The lead may support the pressure of the water it is immersed in, but
the bubble could not support the pressure of the air, if empty within.
4thly. Was ever a visible bubble seen to rise in air? I have made many,
when a boy, with soap-suds and a tobacco-pipe; but they all descended
when loose from the pipe, though slowly, the air impeding their motion.
They may, indeed, be forced up by a wind from below, but do not rise of
themselves, though filled with warm breath.
5thly. The objection relating to our breathing moist air seems weighty,
and must be farther considered. The air that has been breathed has,
doubtless, acquired an addition of the perspirable matter which nature
intends to free the body from, and which would be pernicious if retained
and returned into the blood; such air then may become unfit for respiration,
as well for that reason, as on account of its moisture. Yet I should be glad to
learn, by some accurate experiment, whether a draft of air, two or three
times inspired, and expired, perhaps in a bladder, has, or has not, acquired
more moisture than our common air in the dampest weather. As to the
precipitation of water in the air we breathe, perhaps it is not always a mark
of that air's being overloaded. In the region of the clouds, indeed, the air
must be overloaded if it lets fall its water in drops, which we call rain; but
those drops may fall through a drier air near the earth; and accordingly we
find that the hygroscope sometimes shews a less degree of moisture, during
a shower, than at other times when it does not rain at all. The dewy
dampness, that settles on the insides of our walls and wainscots, seems
more certainly to denote an air overloaded with moisture; and yet this is no
sure sign: for, after a long continued cold season, if the air grows suddenly
warm, the walls, &c. continuing longer their coldness, will, for some time,
condense the moisture of such air, till they grow equally warm, and then
they condense no more, though the air is not become drier. And, on the
other hand, after a warm season, if the air grows cold, though moister than
before, the dew is not so apt to gather on the walls. A tankard of cold water
will, in a hot and dry summer's day, collect a dew on its outside; a tankard
of hot water will collect none in the moistest weather.

6thly. It is, I think, a mistake that the trade-winds blow only in the
afternoon. They blow all day and all night, and all the year round, except in
some particular places. The southerly sea-breezes on your coasts, indeed,
blow chiefly in the afternoon. In the very long run from the west side of
America to Guam, among the Philippine Islands, ships seldom have
occasion to hand their sails, so equal and steady is the gale, and yet they
make it in about 60 days, which could not be if the wind blew only in the
afternoon.
7thly. That really is, which the gentleman justly supposes ought to be on
my hypothesis. In sailing southward, when you first enter the trade-wind,
you find it north-east, or thereabouts, and it gradually grows more east as
you approach the line. The same observation is made of its changing from
south-east to east gradually, as you come from the southern latitudes to the
equator.

Observations on the Meteorological Paper; sent by a Gentleman[10] in New-York to B.
Franklin.

Read at the Royal Society, Nov. 4, 1756.

That power by which the air expands itself, you attribute to a mutual
repelling power in the particles which compose the air, by which they are
separated from each other with some degree of force: now this force, on this
supposition, must not only act when the particles are in mutual contact, but
likewise when they are at some distance from each other. How can two
bodies, whether they be great or small, act at any distance, whether that
distance be small or great, without something intermediate on which they
act? For if any body act on another, at any distance from it, however small
that distance be, without some medium to continue the action, it must act
where it is not, which to me seems absurd.
It seems to me, for the same reason, equally absurd to give a mutual
attractive power between any other particles supposed to be at a distance
from each other, without any thing intermediate to continue their mutual
action. I can neither attract nor repel any thing at a distance, without
something between my hand and that thing, like a string, or a stick; nor can
I conceive any mutual action without some middle thing, when the action is
continued to some distance.
The encrease of the surface of any body lessens its weight, both in air,
and water, or any other fluid, as appears by the slow descent of leaf-gold in
the air.
The observation of the different density of the upper and lower air, from
heat and cold, is good, and I do not remember it is taken notice of by others;
the consequences also are well drawn; but as to winds, they seem
principally to arise from some other cause. Winds generally blow from
some large tracts of land, and from mountains. Where I live, on the north
side of the mountains, we frequently have a strong southerly wind, when
they have as strong a northerly wind, or calm, on the other side of these
mountains. The continual passing of vessels on Hudson's River, through
these mountains, give frequent opportunities of observing this.

In the spring of the year the sea-wind (by a piercing cold) is always more
uneasy to me, accustomed to winds which pass over a tract of land, than the
north-west wind.
You have received the common notion of water-spouts, which, from my
own ocular observation, I am persuaded is a false conception. In a voyage
to the West-Indies, I had an opportunity of observing many water-spouts.
One of them passed nearer than thirty or forty yards to the vessel I was in,
which I viewed with a good deal of attention; and though it be now forty
years since I saw it, it made so strong an impression on me, that I very
distinctly remember it. These water-spouts were in the calm latitudes, that
is, between the trade and the variable winds, in the month of July. That
spout which passed so near us was an inverted cone, with the tip or apex
towards the sea, and reached within about eight feet of the surface of the
sea, its basis in a large black cloud. We were entirely becalmed. It passed
slowly by the vessel. I could plainly observe, that a violent stream of wind
issued from the spout, which made a hollow of about six feet diameter in
the surface of the water, and raised the water in a circular uneven ring round
the hollow, in the same manner that a strong blast from a pair of bellows
would do when the pipe is placed perpendicular to the surface of the water;
and we plainly heard the same hissing noise which such a blast of wind
must produce on the water. I am very sure there was nothing like the
sucking of water from the sea into the spout, unless the spray, which was
raised in a ring to a small height, could be mistaken for a raising of water. I
could plainly distinguish a distance of about eight feet between the sea and
the tip of the cone, in which nothing interrupted the sight, which must have
been, had the water been raised from the sea.
In the same voyage I saw several other spouts at a greater distance, but
none of them whose tip of the cone came so near the surface of the water. In
some of them the axis of the cone was considerably inclined from the
perpendicular, but in none of them was there the least appearance of
sucking up of water. Others of them were bent or arched. I believe that a
stream of wind issued from all of them, and it is from this stream of wind
that vessels are often overset, or founder at sea suddenly. I have heard of
vessels being overset when it was perfectly calm, the instant before the
stream of wind struck them, and immediately after they were overset; which
could not otherwise be but by such a stream of wind from a cloud.

That wind is generated in clouds will not admit of a dispute. Now if such
wind be generated within the body of the cloud, and issue in one particular
place, while it finds no passage in the other parts of the cloud, I think it may
not be difficult to account for all the appearances in water-spouts; and from
hence the reason of breaking those spouts, by firing a cannon-ball through
them, as thereby a horizontal vent is given to the wind. When the wind is
spent, which dilated the cloud, or the fermentation ceases, which generates
the air and wind, the clouds may descend in a prodigious fall of water or
rain. A remarkable intestine motion, like a violent fermentation, is very
observable in the cloud from whence the spout issues. No salt-water, I am
persuaded, was ever observed to fall from the clouds, which must certainly
have happened if sea-water had been raised by a spout.

FOOTNOTE:

[10] Mr. Cadwallader Colden. Editor.

Answer to the foregoing Observations, by B. Franklin.

Read at the Royal Society, Nov. 4, 1756.

I agree with you, that it seems absurd to suppose that a body can act
where it is not. I have no idea of bodies at a distance attracting or repelling
one another without the assistance of some medium, though I know not
what that medium is, or how it operates. When I speak of attraction or
repulsion, I make use of those words for want of others more proper, and
intend only to express effects which I see, and not causes of which I am
ignorant. When I press a blown bladder between my knees, and find I
cannot bring its sides together, but my knees feel a springy matter, pushing
them back to a greater distance, or repelling them, I conclude that the air it
contains is the cause. And when I operate on the air, and find I cannot by
pressure force its particles into contact, but they still spring back against the
pressure, I conceive there must be some medium between its particles that
prevents their closing, though I cannot tell what it is. And if I were

acquainted with that medium, and found its particles to approach and recede
from each other, according to the pressure they suffered, I should imagine
there must be some finer medium between them, by which these operations
were performed.
I allow that increase of the surface of a body may occasion it to descend
slower in air, water, or any other fluid; but do not conceive, therefore, that it
lessens its weight. Where the increased surface is so disposed as that in its
falling a greater quantity of the fluid it sinks in must be moved out of its
way, a greater time is required for such removal. Four square feet of sheet-
lead sinking in water broadways, cannot descend near so fast as it would
edgeways, yet its weight in the hydrostatic balance would, I imagine, be the
same, whether suspended by the middle or by the corner.
I make no doubt but that ridges of high mountains do often interrupt,
stop, reverberate, or turn the winds that blow against them, according to the
different degrees of strength of the winds, and angles of incidence. I
suppose, too, that the cold upper parts of mountains may condense the
warmer air that comes near them, and so by making it specifically heavier,
cause it to descend on one or both sides of the ridge into the warmer
valleys, which will seem a wind blowing from the mountain.
Damp winds, though not colder by the thermometer, give a more uneasy
sensation of cold than dry ones; because (to speak like an electrician) they
conduct better; that is, are better fitted to convey away the heat from our
bodies. The body cannot feel without itself; our sensation of cold is not in
the air without the body, but in those parts of the body which have been
deprived of their heat by the air. My desk, and its lock, are, I suppose, of the
same temperament when they have been long exposed to the same air; but
now if I lay my hand on the wood, it does not seem so cold to me as the
lock; because (as I imagine) wood is not so good a conductor, to receive and
convey away the heat from my skin, and the adjacent flesh, as metal is.
Take a piece of wood, of the size and shape of a dollar, between the thumb
and finger of one hand, and a dollar, in like manner, with the other hand;
place the edges of both, at the same time, in the flame of a candle; and
though the edge of the wooden piece takes flame, and the metal piece does
not, yet you will be obliged to drop the latter before the former, it
conducting the heat more suddenly to your fingers. Thus we can, without
pain, handle glass and china cups filled with hot liquors, as tea, &c. but not

silver ones. A silver tea-pot must have a wooden handle. Perhaps it is for
the same reason that woollen garments keep the body warmer than linen
ones equally thick; woollen keeping the natural heat in, or, in other words,
not conducting it out to air.
In regard to water-spouts, having, in a long letter to a gentleman of the
same sentiment with you as to their direction, said all that I have to say in
support of my opinion; I need not repeat the arguments therein contained, as
I intend to send you a copy of it by some other opportunity, for your
perusal. I imagine you will find all the appearances you saw, accounted for
by my hypothesis. I thank you for communicating the account of them. At
present I would only say, that the opinion of winds being generated in
clouds by fermentation, is new to me, and I am unacquainted with the facts
on which it is founded. I likewise find it difficult to conceive of winds
confined in the body of clouds, which I imagine have little more solidity
than the fogs on the earth's surface. The objection from the freshness of
rain-water is a strong one, but I think I have answered it in the letter above-
mentioned, to which I must beg leave, at present, to refer you.

[In Mr. Collinson's edition, there followed here, several extracts, on
water-spouts, from Dampier's Voyages, which, as Dampier's book is by no
means scarce, and is consequently accessible to the reader, we have
omitted, and shall content ourselves with giving the references. The extracts
are three. The first is from Vol. I. p. 451. The second and third from Vol. III.
p. 182 and 223.]

Gentleman of New York in Reply.

Read at the Royal Society, December 6, 1756.

April 2, 1754.
Any knowledge I have of the winds, and other changes which happen in
the atmosphere, is so very defective, that it does not deserve the name;

neither have I received any satisfaction from the attempts of others on this
subject. It deserves then your thoughts, as a subject in which you may
distinguish yourself, and be useful.
Your notion of some things conducting heat or cold better than others
pleases me, and I wish you may pursue the scent. If I remember right, Dr.
Boerhaave, in his chymistry, thinks that heat is propagated by the vibration
of a subtle elastic fluid, dispersed through the atmosphere and through all
bodies. Sir Isaac Newton says, there are many phenomena to prove the
existence of such a fluid; and this opinion has my assent to it. I shall only
observe that it is essentially different from that which I call ether; for ether,
properly speaking, is neither a fluid nor elastic; its power consists in re-
acting any action communicated to it, with the same force it receives the
action.
I long to see your explication of water-spouts, but I must tell you before-
hand, that it will not be easy for you to convince me that the principal
phenomena were not occasioned by a stream of wind issuing with great
force, my eyes and ears both concurring to give me this sentiment, I could
have no more evidence than to feel the effects, which I had no inclination to
do.
It surprises me a little, that wind, generated by fermentation, is new to
you, since it may be every day observed in fermenting liquor. You know
with what force fermenting liquors will burst the vessels which contain
them, if the generated wind have not vent; and with what force it issues on
giving it a small vent, or by drawing the cork of a bottle. Dr. Boerhaave
says, that the steam issuing from fermenting liquors received through a very
small vent-hole, into the nose, will kill as suddenly and certainly as
lightning. That air is generated by fermentation, I think you will find fully
proved in Dr. Hales's Analysis of the Air, in his Vegetable Statics. If you
have not read the book, you have a new pleasure to come.
The solution you give to the objection I made from the contrary winds
blowing from the opposite sides of the mountains, from their being eddies,
does not please me, because the extent of these winds is by far too large to
be occasioned by any eddy. It is forty miles from New York to our
mountains, through which Hudson's River passes. The river runs twelve
miles in the mountains, and from the north side of the mountains it is about

ninety miles to Albany. I have myself been on board a vessel more than
once, when we have had a strong northerly wind against us, all the way
from New York, for two or three days. We have met vessels from Albany,
who assured us, that, on the other side of the mountains, they had, at the
same time, a strong continued southerly wind against them; and this
frequently happens.
I have frequently seen, both on the river, in places where there could be
no eddy-weeds, and on the open sea, two vessels sailing with contrary
winds, within half a mile of each other; but this happens only in easy winds,
and generally calm in other places near these winds.
You have, no doubt, frequently observed a single cloud pass, from which
a violent gust of wind issues, but of no great extent. I have observed such a
gust make a lane through the woods, of some miles in length, by laying the
trees flat to the ground, and not above eight or ten chains in breadth.
Though the violence of the wind be in the same direction in which the cloud
moves and precedes it, yet wind issues from all sides of it; so that supposing
the cloud moves south-easterly, those on the north-east side of it feel a
south-west wind, and others on the south-west side, a north-east. And where
the cloud passes over, we frequently have a south-east wind from the hinder
part of it, but none violent, except the wind in the direction in which the
cloud moves. To shew what it is which prevents the wind from issuing out
equally on all sides, is not an easy problem to me, and I shall not attempt to
solve it; but when you shall show what it is which restrains the electrical
fluid from spreading itself into the air surrounding it, when it rushes with
great violence through the air along, or in the conductor, for a great extent
in length, then I may hope to explain the other problem, and remove the
difficulty we have in conceiving it.

TO PETER COLLINSON, ESQ. LONDON.

Account of a Whirlwind at Maryland.

Philadelphia, Aug. 25, 1755.
Dear Sir,

As you have my former papers on whirlwinds, &c. I now send you an
account of one which I had lately an opportunity of seeing and examining
myself.
Being in Maryland, riding with Colonel Tasker, and some other
gentlemen, to his country seat, where I and my son were entertained by that
amiable and worthy man with great hospitality and kindness, we saw, in the
vale below us, a small whirlwind beginning in the road, and shewing itself
by the dust it raised and contained. It appeared in the form of a sugar-loaf,
spinning on its point, moving up the hill towards us, and enlarging as it
came forward. When it passed by us, its smaller part near the ground
appeared no bigger than a common barrel, but widening upwards, it
seemed, at forty or fifty feet high, to be twenty or thirty feet in diameter.
The rest of the company stood looking after it, but my curiosity being
stronger, I followed it, riding close by its side, and observed its licking up,
in its progress, all the dust that was under its smaller part. As it is a common
opinion that a shot, fired through a water-spout, will break it, I tried to
break this little whirlwind, by striking my whip frequently through it, but
without any effect. Soon after, it quitted the road and took into the woods,
growing every moment larger and stronger, raising, instead of dust, the old
dry leaves with which the ground was thick covered, and making a great
noise with them and the branches of the trees, bending some tall trees round
in a circle swiftly and very surprisingly, though the progressive motion of
the whirl was not so swift but that a man on foot might have kept pace with
it, but the circular motion was amazingly rapid. By the leaves it was now
filled with, I could plainly perceive that the current of air they were driven
by moved upwards in a spiral line; and when I saw the passing whirl
continue entire, after leaving the trunks and bodies of large trees which it
had enveloped, I no longer wondered that my whip had no effect on it in its
smaller state. I accompanied it about three quarters of a mile, till some
limbs of dead trees, broken off by the whirl, flying about, and falling near
me, made me more apprehensive of danger; and then I stopped, looking at
the top of it as it went on, which was visible, by means of the leaves
contained in it, for a very great height above the trees. Many of the leaves,
as they got loose from the upper and widest part, were scattered in the wind;
but so great was their height in the air, that they appeared no bigger than
flies. My son, who was, by this time, come up with me, followed the
whirlwind till it left the woods, and crossed an old tobacco-field, where,

finding neither dust nor leaves to take up, it gradually became invisible
below as it went away over that field. The course of the general wind then
blowing was along with us as we travelled, and the progressive motion of
the whirlwind was in a direction nearly opposite, though it did not keep a
strait line, nor was its progressive motion uniform, it making little sallies on
either hand as it went, proceeding sometimes faster, and sometimes slower,
and seeming sometimes for a few seconds almost stationary, then starting
forwards pretty fast again. When we rejoined the company, they were
admiring the vast height of the leaves now brought by the common wind,
over our heads. These leaves accompanied us as we travelled, some falling
now and then round about us, and some not reaching the ground till we had
gone near three miles from the place where we first saw the whirlwind
begin. Upon my asking Colonel Tasker if such whirlwinds were common in
Maryland, he answered pleasantly, No, not at all common, but we got this
on purpose to treat Mr. Franklin. And a very high treat it was to,
Dear Sir,
Your affectionate friend and humble servant,
B. FRANKLIN.

TO MR. ALEXANDER SMALL, LONDON.

On the North-East Storms in North America.

May 12, 1760.
Dear Sir,
Agreeable to your request, I send you my reasons for thinking that our
north-east storms in North America begin first, in point of time, in the
south-west parts: that is to say, the air in Georgia, the farthest of our
colonies to the south-west, begins to move south-westerly before the air of
Carolina, which is the next colony north-eastward; the air of Carolina has
the same motion before the air of Virginia, which lies still more north-
eastward; and so on north-easterly through Pensylvania, New-York, New-
England, &c. quite to Newfoundland.
These north-east storms are generally very violent, continue sometimes
two or three days, and often do considerable damage in the harbours along
the coast. They are attended with thick clouds and rain.
What first gave me this idea, was the following circumstance. About
twenty years ago, a few more or less, I cannot from my memory be certain,
we were to have an eclipse of the moon at Philadelphia, on a Friday
evening, about nine o'clock. I intended to observe it, but was prevented by a
north-east storm, which came on about seven, with thick clouds as usual,
that quite obscured the whole hemisphere. Yet when the post brought us the
Boston news-paper, giving an account of the effects of the same storm in
those parts, I found the beginning of the eclipse had been well observed
there, though Boston lies N. E. of Philadelphia about four hundred miles.
This puzzled me, because the storm began with us so soon as to prevent any
observation, and being a north-east storm, I imagined it must have begun
rather sooner in places farther to the north-east-ward than it did at
Philadelphia. I therefore mentioned it in a letter to my brother, who lived at
Boston; and he informed me the storm did not begin with them till near
eleven o'clock, so that they had a good observation of the eclipse: and upon
comparing all the other accounts I received from the several colonies, of the
time of beginning of the same storm, and since that of other storms of the
same kind, I found the beginning to be always later the farther north-

eastward. I have not my notes with me here in England, and cannot, from
memory, say the proportion of time to distance, but I think it is about an
hour to every hundred miles.
From thence I formed an idea of the cause of these storms, which I would
explain by a familiar instance or two.—Suppose a long canal of water
stopped at the end by a gate. The water is quite at rest till the gate is open,
then it begins to move out through the gate; the water next the gate is first
in motion, and moves towards the gate; the water next to that first water
moves next, and so on successively, till the water at the head of the canal is
in motion, which is last of all. In this case all the water moves indeed
towards the gate, but the successive times of beginning motion are the
contrary way, viz. from the gate backwards to the head of the canal. Again,
suppose the air in a chamber at rest, no current through the room till you
make a fire in the chimney. Immediately the air in the chimney being
rarefied by the fire rises; the air next the chimney flows in to supply its
place, moving towards the chimney; and, in consequence, the rest of the air
successively, quite back to the door. Thus to produce our north-east storms,
I suppose some great heat and rarefaction of the air in or about the Gulph of
Mexico; the air thence rising has its place supplied by the next more
northern, cooler, and therefore denser and heavier, air; that, being in motion,
is followed by the next more northern air, &c. &c. in a successive current,
to which current our coast and inland ridge of mountains give the direction
of north-east, as they lie N. E. and S. W.
This I offer only as an hypothesis to account for this particular fact; and
perhaps, on farther examination, a better and truer may be found. I do not
suppose all storms generated in the same manner. Our north-west thunder-
gusts in America, I know are not; but of them I have written my opinion
fully in a paper which you have seen.
I am, &c.
B. FRANKLIN.

Meteorological Imaginations and Conjectures[11].

There seems to be a region higher in the air over all countries, where it is
always winter, where frost exists continually, since in the midst of summer,
on the surface of the earth, ice falls often from above in the form of hail.
Hailstones, of the great weight we sometimes find them, did not probably
acquire their magnitude before they began to descend. The air, being eight
hundred times rarer than water, is unable to support it but in the shape of
vapour, a state in which its particles are separated. As soon as they are
condensed by the cold of the upper region, so as to form a drop, that drop
begins to fall. If it freezes into a grain of ice, that ice descends. In
descending, both the drop of water and the grain of ice are augmented by
particles of the vapour they pass through in falling, and which they
condense by coldness, and attach to themselves.
It is possible that, in summer, much of what is rain, when it arrives at the
surface of the earth, might have been snow when it began its descent; but
being thawed, in passing through the warm air near the surface, it is
changed from snow into rain.
How immensely cold must be the original particle of hail, which forms
the centre of the future hailstone, since it is capable of communicating
sufficient cold, if I may so speak, to freeze all the mass of vapour
condensed round it, and form a lump of perhaps six or eight ounces in
weight!
When, in summer time, the sun is high, and continues long every day
above the horizon, his rays strike the earth more directly, and with longer
continuance, than in the winter; hence the surface is more heated, and to a
greater depth, by the effect of those rays.
When rain falls on the heated earth, and soaks down into it, it carries
down with it a great part of the heat, which by that means descends still
deeper.
The mass of earth, to the depth perhaps of thirty feet, being thus heated to
a certain degree, continues to retain its heat for some time. Thus the first
snows that fall in the beginning of winter, seldom lie long on the surface,
but are soon melted, and soon absorbed. After which, the winds, that blow
over the country on which the snows had fallen, are not rendered so cold as
they would have been, by those snows, if they had remained, and thus the

approach of the severity of winter is retarded; and the extreme degree of its
cold is not always at the time we might expect it, viz. when the sun is at its
greatest distance, and the day shortest, but some time after that period,
according to the English proverb, which says, "as the day lengthens, the
cold strengthens;" the causes of refrigeration continuing to operate, while
the sun returns too slowly, and his force continues too weak to counteract
them.
During several of the summer months of the year 1783, when the effects
of the sun's rays to heat the earth in these northern regions should have been
the greatest, there existed a constant fog over all Europe, and great part of
North America. This fog was of a permanent nature: it was dry, and the rays
of the sun seemed to have little effect towards dissipating it, as they easily
do a moist fog, arising from water. They were indeed rendered so faint in
passing through it, that when collected in the focus of a burning glass, they
would scarce kindle brown paper. Of course, their summer effect in heating
the earth was exceedingly diminished.
Hence the surface was early frozen.
Hence the first snows remained on it unmelted, and received continual
additions.
Hence perhaps the winter of 1783-4, was more severe than any that had
happened for many years.
The cause of this universal fog is not yet ascertained. Whether it was
adventitious to this earth, and merely a smoke proceeding from the
consumption by fire of some of those great burning balls or globes which
we happen to meet with in our rapid course round the sun, and which are
sometimes seen to kindle and be destroyed in passing our atmosphere, and
whose smoke might be attracted and retained by our earth; or whether it
was the vast quantity of smoke, long continuing to issue during the summer
from Hecla, in Iceland, and that other volcano which arose out of the sea
near that island, which smoke might be spread by various winds, over the
northern part of the world, is yet uncertain.
It seems however worth the enquiry, whether other hard winters,
recorded in history, were preceded by similar permanent and widely
extended summer fogs. Because, if found to be so, men might from such

fogs conjecture the probability of a succeeding hard winter, and of the
damage to be expected by the breaking up of frozen rivers in the spring; and
take such measures as are possible and practicable, to secure themselves
and effects from the mischiefs that attended the last.
Passy, May 1784.

FOOTNOTE:

[11] This paper is taken from the Memoirs of the Literary and Philosophical
Society of Manchester, Vol. II. page 373. It was communicated by Dr. Percival,
and read December 22, 1784. Editor.

Suppositions and Conjectures towards forming an Hypothesis, for the Explanation of the
Aurora Borealis[12].

1. Air heated by any means, becomes rarefied, and specifically lighter
than other air in the same situation not heated.
2. Air being made thus lighter rises, and the neighbouring cooler heavier
air takes its place.
3. If in the middle of a room you heat the air by a stove, or pot of burning
coals near the floor, the heated air will rise to the ceiling, spread over the
cooler air till it comes to the cold walls; there, being condensed and made
heavier, it descends to supply the place of that cool air, which had moved
towards the stove or fire, in order to supply the place of the heated air,
which had ascended from the space around the stove or fire.
4. Thus there will be a continual circulation of air in the room; which
may be rendered visible by making a little smoke, for that smoke will rise
and circulate with the air.
5. A similar operation is performed by nature on the air of this globe. Our
atmosphere is of a certain height, perhaps at a medium [ ] miles: above
that height it is so rare as to be almost a vacuum. The air heated between the

tropics is continually rising; its place is supplied by northerly and southerly
winds, which come from the cooler regions.
6. The light heated air, floating above the cooler and denser, must spread
northward and southward; and descend near the two poles, to supply the
place of the cool air, which had moved towards the equator.
7. Thus a circulation of air is kept up in our atmosphere, as in the room
above-mentioned.
8. That heavier and lighter air may move in currents of different and even
opposite direction, appears sometimes by the clouds that happen to be in
those currents, as plainly as by the smoke in the experiment above-
mentioned. Also in opening a door between two chambers, one of which
has been warmed, by holding a candle near the top, near the bottom, and
near the middle, you will find a strong current of warm air passing out of
the warmed room above, and another of cool air entering below; while in
the middle there is little or no motion.
9. The great quantity of vapour rising between the tropics forms clouds,
which contain much electricity.
Some of them fall in rain, before they come to the polar regions.
10. If the rain be received in an isolated vessel, the vessel will be
electrified; for every drop brings down some electricity with it.
11. The same is done by snow or hail.
12. The electricity so descending, in temperate climates, is received and
imbibed by the earth.
13. If the clouds are not sufficiently discharged by this gradual operation,
they sometimes discharge themselves suddenly by striking into the earth,
where the earth is fit to receive their electricity.
14. The earth in temperate and warm climates is generally fit to receive
it, being a good conductor.
15. A certain quantity of heat will make some bodies good conductors,
that will not otherwise conduct.
16. Thus wax rendered fluid, and glass softened by heat, will both of
them conduct.

17. And water, though naturally a good conductor, will not conduct well,
when frozen into ice by a common degree of cold; not at all, where the cold
is extreme.
18. Snow falling upon frozen ground has been found to retain its
electricity; and to communicate it to an isolated body, when after falling, it
has been driven about by the wind.
19. The humidity, contained in all the equatorial clouds that reach the
polar regions, must there be condensed and fall in snow.
20. The great cake of ice that eternally covers those regions may be too
hard frozen to permit the electricity, descending with that snow, to enter the
earth.
21. It may therefore be accumulated upon that ice.
22. The atmosphere being heavier in the polar regions than in the
equatorial, will there be lower; as well from that cause, as from the smaller
effect of the centrifugal force: consequently the distance of the vacuum
above the atmosphere will be less at the poles, than elsewhere; and probably
much less than the distance (upon the surface of the globe) extending from
the pole to those latitudes in which the earth is so thawed as to receive and
imbibe electricity; (the frost continuing to lat. 80, which is ten degrees, or
six hundred miles from the pole; while the height of the atmosphere there of
such density as to obstruct the motion of the electric fluid, can scarce be
esteemed above [ ] miles).
23. The vacuum above is a good conductor.
24. May not then the great quantity of electricity, brought into the polar
regions by the clouds, which are condensed there, and fall in snow, which
electricity would enter the, earth, but cannot penetrate the ice; may it not, I
say, (as a bottle overcharged) break through that low atmosphere, and run
along in the vacuum over the air towards the equator; diverging as the
degrees of longitude enlarge; strongly visible where densest, and becoming
less visible as it more diverges; till it finds a passage to the earth in more
temperate climates, or is mingled with their upper air?
25. If such an operation of nature were really performed, would it not
give all the appearances of an aurora borealis?

26. And would not the auroras become more frequent after the approach
of winter: not only because more visible in longer nights; but also because
in summer the long presence of the sun may soften the surface of the great
ice cake, and render it a conductor, by which the accumulation of electricity
in the polar regions will be prevented?
27. The atmosphere of the polar regions being made more dense by the
extreme cold, and all the moisture in that air being frozen; may not any
great light arising therein, and passing, through it, render its density in some
degree visible, during the night time, to those who live in the rarer air of
more southern latitudes; and would it not in that case, although in itself a
complete and full circle, extending perhaps ten degrees from the pole,
appear to spectators so placed (who could see only a part of it) in the form
of a segment; its chord resting on the horizon, and its arch elevated more or
less above it as seen from latitudes more or less distant; darkish in colour,
but yet sufficiently transparent to permit some stars to be seen through it.
28. The rays of electric matter issuing out of a body, diverge by mutually
repelling each other, unless there be some conducting body near, to receive
them: and if that conducting body be at a greater distance, they will first
diverge, and then converge in order to enter it. May not this account for
some of the varieties of figure seen at times in the motions of the luminous
matter of the auroras: since it is possible, that in passing over the
atmosphere, from the north in all directions or meridians, towards the
equator, the rays of that matter may find, in many places, portions of cloudy
region, or moist atmosphere under them, which (being in the natural or
negative state) may be fit to receive them, and towards which they may
therefore converge: and when one of those receiving bodies is more than
saturated, they may again diverge from it, towards other surrounding
masses of such humid atmosphere, and thus form the crowns, as they are
called, and other figures mentioned in the histories of this meteor?
29. If it be true that the clouds which go to the polar regions, and carry
thither the vapours of the equatorial and temperate regions, [have their]
vapours condensed by the extreme cold of the polar regions, and fall in
snow or hail; the winds which come from those regions ought to be
generally dry, unless they gain some humidity by sweeping the ocean in
their way. And if I mistake not, the winds between the north east and the

north west, are for the most part dry, when they have continued for some
time.

[In the Philosophical Transactions for 1774, p. 122, is a letter from Mr. I.
S. Winn to Dr. Franklin, stating, that since he had first made the observation
concerning the south or south west winds succeeding an aurora, he had
found it invariably obtaining in twenty-three instances; and he adds in a
note a fresh confirming instance. In reply, Dr. Franklin makes the following
conjecture.]
The Auroræ Boreales, though visible almost every night of clear weather
in the more northern regions and very high in the atmosphere, can scarce be
visible in England, but when the atmosphere is pretty clear of clouds for the
whole space between us and those regions; and therefore are seldom visible
here. This extensive clearness may have been produced by a long
continuance of northerly winds. When the winds have long continued in one
quarter, the return is often violent. Allowing the fact so repeatedly observed
by Mr. Winn, perhaps this may account for the violence of the southerly
winds, that soon follow the appearance of the aurora on our coasts.

FOOTNOTES:

[12] If I mistake not, this paper was read to the Royal Academy of Sciences, at
Paris, at the meeting held immediately after Easter, 1779. B. V[13].
[13] For an explanation of the signature B. V. see the note in page 399 of Vol. I.
Editor.

T O D R . L . [ 1 4 ] AT C H A R L E S - T O W N , S O U T H - C A R O L I N A .

On Cold produced by Evaporation.

New-York, April 14, 1757.
Sir,
It is a long time since I had the pleasure of a line from you; and, indeed,
the troubles of our country, with the hurry of business I have been engaged
in on that account, have made me so bad a correspondent, that I ought not to
expect punctuality in others.
But being about to embark for England, I could not quit the continent
without paying my respects to you, and, at the same time, taking leave to
introduce to your acquaintance a gentleman of learning and merit, colonel
Henry Bouquet, who does me the favour to present you this letter, and with
whom I am sure you will be much pleased.
Professor Simpson, of Glasgow, lately communicated to me some curious
experiments of a physician of his acquaintance, by which it appeared, that
an extraordinary degree of cold, even to freezing, might be produced by
evaporation. I have not had leisure to repeat and examine more than the first
and easiest of them, viz.—Wet the ball of a thermometer by a feather dipt in
spirit of wine, which has been kept in the same room, and has, of course,
the same degree of heat or cold. The mercury sinks presently three or four
degrees, and the quicker, if, during the evaporation, you blow on the ball
with bellows; a second wetting and blowing, when the mercury is down,
carries it yet lower. I think I did not get it lower than five or six degrees
from where it naturally stood, which was, at that time, sixty. But it is said,
that a vessel of water being placed in another somewhat larger, containing
spirit, in such a manner that the vessel of water is surrounded with the
spirit, and both placed under the receiver of an air-pump; on exhausting the
air, the spirit, evaporating, leaves such a degree of cold as to freeze the
water, though the thermometer, in the open air, stands many degrees above
the freezing point.
I know not how this phenomenon is to be accounted for, but it gives me
occasion to mention some loose notions relating to heat and cold, which I
have for some time entertained, but not yet reduced into any form. Allowing
common fire, as well as electrical, to be a fluid capable of permeating other
bodies, and seeking an equilibrium, I imagine some bodies are better fitted
by nature to be conductors of that fluid than others; and that, generally,

those which are the best conductors of the electrical fluid, are also the best
conductors of this; and e contra.
Thus a body which is a good conductor of fire readily receives it into its
substance, and conducts it through the whole to all the parts, as metals and
water do; and if two bodies, both good conductors, one heated, the other in
its common state, are brought into contact with each other, the body which
has most fire readily communicates of it to that which had least, and that
which had least readily receives it, till an equilibrium is produced. Thus, if
you take a dollar between your fingers with one hand, and a piece of wood,
of the same dimensions, with the other, and bring both at the same time to
the flame of a candle, you will find yourself obliged to drop the dollar
before you drop the wood, because it conducts the heat of the candle sooner
to your flesh. Thus, if a silver tea-pot had a handle of the same metal, it
would conduct the heat from the water to the hand, and become too hot to
be used; we therefore give to a metal tea-pot a handle of wood, which is not
so good a conductor as metal. But a china or stone tea-pot being in some
degree of the nature of glass, which is not a good conductor of heat, may
have a handle of the same stuff. Thus, also, a damp moist air shall make a
man more sensible of cold, or chill him more, than a dry air that is colder,
because a moist air is fitter to receive and conduct away the heat of his
body. This fluid, entering bodies in great quantity, first expands them, by
separating their parts a little, afterwards, by farther separating their parts, it
renders solids fluid, and at length dissipates their parts in air. Take this fluid
from melted lead, or from water, the parts cohere again, the first grows
solid, the latter becomes ice: and this is sooner done by the means of good
conductors.
Thus, if you take, as I have done, a square bar
of lead, four inches long, and one inch thick,
together with three pieces of wood planed to the
same dimensions, and lay them, as in the
margin, on a smooth board, fixt so as not to be
easily separated or moved, and pour into the
cavity they form, as much melted lead as will
fill it, you will see the melted lead chill, and
become firm, on the side next the leaden bar,
some time before it chills on the other three

sides in contact with the wooden bars, though before the lead was poured
in, they might all be supposed to have the same degree of heat or coldness,
as they had been exposed in the same room to the same air. You will
likewise observe, that the leaden bar, as it has cooled the melted lead more
than the wooden bars have done, so it is itself more heated by the melted
lead. There is a certain quantity of this fluid called fire, in every living
human body, which fluid, being in due proportion, keeps the parts of the
flesh and blood at such a just distance from each other, as that the flesh and
nerves are supple, and the blood fit for circulation. If part of this due
proportion of fire be conducted away, by means of a contact with other
bodies, as air, water, or metals, the parts of our skin and flesh that come into
such contact first draw more near together than is agreeable, and give that
sensation which we call cold; and if too much be conveyed away, the body
stiffens, the blood ceases to flow, and death ensues. On the other hand, if
too much of this fluid be communicated to the flesh, the parts are separated
too far, and pain ensues, as when they are separated by a pin or lancet. The
sensation that the separation by fire occasions, we call heat, or burning. My
desk on which I now write, and the lock of my desk, are both exposed to the
same temperature of the air, and have therefore the same degree of heat or
cold; yet if I lay my hand successively on the wood and on the metal, the
latter feels much the coldest, not that it is really so, but being a better
conductor, it more readily than the wood takes away and draws into itself
the fire that was in my skin. Accordingly if I lay one hand, part on the lock,
and part on the wood, and after it had lain so some time, I feel both parts
with my other hand, I find the part that has been in contact with the lock,
very sensibly colder to the touch, than the part that lay on the wood. How a
living animal obtains its quantity of this fluid called fire, is a curious
question. I have shown, that some bodies (as metals) have a power of
attracting it stronger than others; and I have sometimes suspected, that a
living body had some power of attracting out of the air, or other bodies, the
heat it wanted. Thus metals hammered, or repeatedly bent, grow hot in the
bent or hammered part. But when I consider that air, in contact with the
body, cools it; that the surrounding air is rather heated by its contact with
the body; that every breath of cooler air drawn in, carries off part of the
body's heat when it passes out again; that therefore there must be in the
body a fund for producing it, or otherwise the animal would soon grow
cold; I have been rather inclined to think, that the fluid fire, as well as the

fluid air, is attracted by plants in their growth, and becomes consolidated
with the other materials of which they are formed, and makes a great part of
their substance: that when they come to be digested, and to suffer in the
vessels a kind of fermentation, part of the fire, as well as part of the air,
recovers its fluid active state again, and diffuses itself in the body digesting
and separating it: that the fire so reproduced, by digestion and separation
continually leaving the body, its place is supplied by fresh quantities,
arising from the continual separation. That whatever quickens the motion of
the fluids in an animal quickens the separation, and reproduces more of the
fire; as exercise. That all the fire emitted by wood, and other combustibles,
when burning, existed in them before, in a solid state, being only discovered
when separating. That some fossils, as sulphur, sea-coal, &c. contain a great
deal of solid fire; and that, in short, what escapes and is dissipated in the
burning of bodies, besides water and earth, is generally the air and fire that
before made parts of the solid. Thus I imagine that animal heat arises by or
from a kind of fermentation in the juices of the body, in the same manner as
heat arises in the liquors preparing for distillation, wherein there is a
separation of the spirituous, from the watry and earthy parts. And it is
remarkable, that the liquor in a distiller's vat, when in its highest and best
state of fermentation, as I have been informed, has the same degree of heat
with the human body; that is, about 94 or 96.
Thus, as by a constant supply of fuel in a chimney, you keep a warm
room, so, by a constant supply of food in the stomach, you keep a warm
body; only where little exercise is used, the heat may possibly be conducted
away too fast; in which case such materials are to be used for cloathing and
bedding, against the effects of an immediate contact of the air, as are, in
themselves, bad conductors of heat, and, consequently, prevent its being
communicated through their substance to the air. Hence what is called
warmth in wool, and its preference on that account, to linen; wool not being
so good a conductor: and hence all the natural coverings of animals, to keep
them warm, are such as retain and confine the natural heat in the body, by
being bad conductors, such as wool, hair, feathers, and the silk by which the
silk-worm, in its tender embrio state, is first cloathed. Cloathing, thus
considered, does not make a man warm by giving warmth, but by
preventing the too quick dissipation of the heat produced in his body, and so
occasioning an accumulation.

There is another curious question I will just venture to touch upon, viz.
Whence arises the sudden extraordinary degree of cold, perceptible on
mixing some chemical liquors, and even on mixing salt and snow, where
the composition appears colder than the coldest of the ingredients? I have
never seen the chemical mixtures made, but salt and snow I have often
mixed myself, and am fully satisfied that the composition feels much colder
to the touch, and lowers the mercury in the thermometer more than either
ingredient would do separately. I suppose, with others, that cold is nothing
more than the absence of heat or fire. Now if the quantity of fire before
contained or diffused in the snow and salt was expelled in the uniting of the
two matters, it must be driven away either through the air or the vessel
containing them. If it is driven off thro' the air, it must warm the air, and a
thermometer held over the mixture, without touching it, would discover the
heat, by the rising of the mercury, as it must, and always does in warm air.
This, indeed, I have not tried, but I should guess it would rather be driven
off through the vessel, especially if the vessel be metal, as being a better
conductor than air; and so one should find the bason warmer after such
mixture. But, on the contrary, the vessel grows cold, and even water, in
which the vessel is sometimes placed for the experiment, freezes into hard
ice on the bason. Now I know not how to account for this, otherwise than
by supposing, that the composition is a better conductor of fire than the
ingredients separately, and, like the lock compared with the wood, has a
stronger power of attracting fire, and does accordingly attract it suddenly
from the fingers, or a thermometer put into it, from the bason that contains
it, and from the water in contact with the outside of the bason; so that the
fingers have the sensation of extreme cold, by being deprived of much of
their natural fire; the thermometer sinks, by having part of its fire drawn out
of the mercury; the bason grows colder to the touch, as, by having its fire
drawn into the mixture, it is become more capable of drawing and receiving
it from the hand; and through the bason, the water loses its fire that kept it
fluid; so it becomes ice. One would expect, that from all this attracted
acquisition of fire to the composition, it should become warmer; and, in
fact, the snow and salt dissolve at the same time into water, without
freezing.
I am, Sir, &c.
B. FRANKLIN.

FOOTNOTE:

[14] Dr. Lining. Editor.

TO THE SAME ON THE SAME SUBJECT.

London, June 17, 1758.
Dear Sir,
In a former letter I mentioned the experiment for cooling bodies by
evaporation, and that I had, by repeatedly wetting the thermometer with
common spirits, brought the mercury down five or six degrees. Being lately
at Cambridge, and mentioning this in conversation with Dr. Hadley,
professor of chemistry there, he proposed repeating the experiments with
ether, instead of common spirits, as the ether is much quicker in
evaporation. We accordingly went to his chamber, where he had both ether
and a thermometer. By dipping first the ball of the thermometer into the
ether, it appeared that the ether was precisely of the same temperament with
the thermometer, which stood then at 65; for it made no alteration in the
height of the little column of mercury. But when the thermometer was taken
out of the ether, and the ether, with which the ball was wet, began to
evaporate, the mercury sunk several degrees. The wetting was then repeated
by a feather that had been dipped into the ether, when the mercury sunk still
lower. We continued this operation, one of us wetting the ball, and another
of the company blowing on it with the bellows, to quicken the evaporation,
the mercury sinking all the time, till it came down to 7, which is 25 degrees
below the freezing point, when we left off. Soon after it passed the freezing
point, a thin coat of ice began to cover the ball. Whether this was water
collected and condensed by the coldness of the ball, from the moisture in
the air, or from our breath; or whether the feather, when dipped into the
ether, might not sometimes go through it, and bring up some of the water
that was under it, I am not certain; perhaps all might contribute. The ice
continued increasing till we ended the experiment, when it appeared near a
quarter of an inch thick all over the ball, with a number of small spicula,

pointing outwards. From this experiment one may see the possibility of
freezing a man to death on a warm summer's day, if he were to stand in a
passage through which the wind blew briskly, and to be wet frequently with
ether, a spirit that is more inflammable than brandy, or common spirits of
wine.
It is but within these few years, that the European philosophers seem to
have known this power in nature, of cooling bodies by evaporation. But in
the east they have long been acquainted with it. A friend tells me, there is a
passage in Bernier's Travels through Indostan, written near one hundred
years ago, that mentions it as a practice (in travelling over dry deserts in
that hot climate) to carry water in flasks wrapt in wet woollen cloths, and
hung on the shady side of the camel, or carriage, but in the free air;
whereby, as the cloths gradually grow drier, the water contained in the
flasks is made cool. They have likewise a kind of earthen pots, unglazed,
which let the water gradually and slowly ooze through their pores, so as to
keep the outside a little wet, notwithstanding the continual evaporation,
which gives great coldness to the vessel, and the water contained in it. Even
our common sailors seem to have had some notion of this property; for I
remember, that being at sea, when I was a youth, I observed one of the
sailors, during a calm in the night, often wetting his finger in his mouth, and
then holding it up in the air, to discover, as he said, if the air had any
motion, and from which side it came; and this he expected to do, by finding
one side of his finger grow suddenly cold, and from that side he should look
for the next wind; which I then laughed at as a fancy.
May not several phenomena, hitherto unconsidered, or unaccounted for,
be explained by this property? During the hot Sunday at Philadelphia, in
June 1750, when the thermometer was up at 100 in the shade, I sat in my
chamber without exercise, only reading or writing, with no other cloaths on
than a shirt, and a pair of long linen drawers, the windows all open, and a
brisk wind blowing through the house, the sweat ran off the backs of my
hands, and my shirt was often so wet, as to induce me to call for dry ones to
put on; in this situation, one might have expected, that the natural heat of
the body 96, added to the heat of the air 100, should jointly have created or
produced a much greater degree of heat in the body; but the fact was, that
my body never grew so hot as the air that surrounded it, or the inanimate
bodies immersed in the same air. For I remember well, that the desk, when I

laid my arm upon it; a chair, when I sat down in it; and a dry shirt out of the
drawer, when I put it on, all felt exceeding warm to me, as if they had been
warmed before a fire. And I suppose a dead body would have acquired the
temperature of the air, though a living one, by continual sweating, and by
the evaporation of that sweat, was kept cold. May not this be a reason why
our reapers in Pensylvania, working in the open field, in the clear hot sun-
shine common in our harvest-time[15], find themselves well able to go
through that labour, without being much incommoded by the heat, while
they continue to sweat, and while they supply matter for keeping up that
sweat, by drinking frequently of a thin evaporable liquor, water mixed with
rum; but if the sweat stops, they drop, and sometimes die suddenly, if a
sweating is not again brought on by drinking that liquor, or, as some rather
chuse in that case, a kind of hot punch, made with water, mixed with honey,
and a considerable proportion of vinegar? May there not be in negroes a
quicker evaporation of the perspirable matter from their skins and lungs,
which, by cooling them more, enables them to bear the sun's heat better
than whites do? (if that is a fact, as it is said to be; for the alledged necessity
of having negroes rather than whites, to work in the West-India fields, is
founded upon it) though the colour of their skins would otherwise make
them more sensible of the sun's heat, since black cloth heats much sooner,
and more, in the sun, than white cloth. I am persuaded, from several
instances happening within my knowledge, that they do not bear cold
weather so well as the whites; they will perish when exposed to a less
degree of it, and are more apt to have their limbs frostbitten; and may not
this be from the same cause? Would not the earth grow much hotter under
the summer-sun, if a constant evaporation from its surface, greater as the
sun shines stronger, did not, by tending to cool it; balance, in some degree,
the warmer effects of the sun's rays? Is it not owing to the constant
evaporation from the surface of every leaf, that trees, though shone on by
the sun, are always, even the leaves themselves, cool to our sense? at least
much cooler than they would otherwise be? May it not be owing to this, that
fanning ourselves when warm, does really cool us, though the air is itself
warm that we drive with the fan upon our faces; for the atmosphere round,
and next to our bodies, having imbibed as much of the perspired vapour as
it can well contain, receives no more, and the evaporation is therefore
checked and retarded, till we drive away that atmosphere, and bring drier
air in its place, that will receive the vapour, and thereby facilitate and

increase the evaporation? Certain it is, that mere blowing of air on a dry
body does not cool it, as any one may satisfy himself, by blowing with a
bellows on the dry ball of a thermometer; the mercury will not fall; if it
moves at all, it rather rises, as being warmed by the friction of the air on its
surface? To these queries of imagination, I will only add one practical
observation; that wherever it is thought proper to give ease, in cases of
painful inflammation in the flesh (as from burnings, or the like) by cooling
the part; linen cloths, wet with spirit, and applied to the part inflamed, will
produce the coolness required, better than if wet with water, and will
continue it longer. For water, though cold when first applied, will soon
acquire warmth from the flesh, as it does not evaporate fast enough; but the
cloths wet with spirit, will continue cold as long as any spirit is left to keep
up the evaporation, the parts warmed escaping as soon as they are warmed,
and carrying off the heat with them.
I am, Sir, &c.
B FRANKLIN.

FOOTNOTE:

[15] Pensylvania is in about lat. 40, and the sun, of course, about 12 degrees
higher, and therefore much hotter than in England. Their harvest is about the end
of June, or beginning of July, when the sun is nearly at the highest.

J. B.[16] ESQ. IN BOSTON, TO B. FRANKLIN.

Concerning the Light in Sea-Water.

Read at the Royal Society, December 6, 1756.

November 12, 1753.
**** When I was at the eastward, I had an opportunity of observing the
luminous appearance of the sea when disturbed: at the head and stern of the
vessel, when under way, it appeared very bright. The best opportunity I had
to observe it was in a boat, in company with several gentlemen going from
Portsmouth, about three miles, to our vessel lying at the mouth of
Piscataqua River. Soon after we set off (it being in the evening) we
observed a luminous appearance, where the oars dashed the water.
Sometimes it was very bright, and afterwards, as we rowed along, gradually
lessened, till almost imperceptible, and then re-illumined. This we took
notice of several times in the passage. When I got on board the vessel, I
ordered a pail to be dipped up, full of sea-water, in which, on the water's
being moved, a sparkling light appeared. I took a linen cloth, and strained
some of the water through it, and there was a like appearance on the cloth,
which soon went off; but on rubbing the cloth with my finger, it was
renewed. I then carried the cloth to the light, but could not perceive any
thing upon it which should cause that appearance.
Several gentlemen were of opinion, that the separated particles of putrid,
animal, and other bodies, floating on the surface of the sea, might cause that
appearance; for putrid fish, &c. they said, will cause it: and the sea-animals
which have died, and other bodies putrified therein since the creation, might
afford a sufficient quantity of these particles to cover a considerable portion
of the surface of the sea; which particles being differently dispersed, might
account for the different degrees of light in the appearance above-
mentioned. But this account seems liable to this obvious objection, that as
putrid fish, &c. make a luminous appearance without being moved or
disturbed, it might be expected that the supposed putrid particles on the
surface of the sea, should always appear luminous, where there is not a

greater light; and, consequently, that the whole surface of the sea, covered
with those particles, should always, in dark nights, appear luminous,
without being disturbed. But this is not fact.
Among the rest, I threw out my conjecture, that the said appearance
might be caused by a great number of little animals, floating on the surface
of the sea, which, on being disturbed, might, by expanding their finns, or
otherwise moving themselves, expose such a part of their bodies as exhibits
a luminous appearance, somewhat in the manner of a glow-worm, or fire-
fly: that these animals may be more numerous in some places than others;
and, therefore, that the appearance above-mentioned being fainter and
stronger in different places, might be owing to that: that certain
circumstances of weather, &c. might invite them to the surface, on which,
in a calm, they might sport themselves and glow; or in storms, being forced
up, make the same appearance.
There is no difficulty in conceiving that the sea may be stocked with
animalcula for this purpose, as we find all nature crowded with life. But it
seems difficult to conceive that such small portions of matter, even if they
were wholly luminous, should affect our sight; much more so, when it is
supposed that only a part of them is luminous. But, if we consider some
other appearances, we may find the same difficulty to conceive of them;
and yet we know they take place. For instance, the flame of a candle,
which, it is said, may be seen four miles round. The light which fills this
circle of eight miles diameter, was contained, when it first left the candle,
within a circle of half an inch diameter. If the density of light, in these
circumstances, be as those circles to each other, that is, as the squares of
their diameters, the candle-light, when come to the eye, will be
1027709337600 times rarer than when it quitted the half inch circle. Now
the aperture of the eye, through which the light passes, does not exceed one-
tenth of an inch diameter, and the portion of the lesser circle, which
corresponds to this small portion of the greater circle, must be
proportionably, that is, 1027709337600 times less than one-tenth of an inch;
and yet this infinitely small point (if you will allow the expression) affords
light enough to make it visible four miles; or, rather, affords light sufficient
to affect the sight at that distance.
The smallness of the animalcula is no objection then to this conjecture;
for supposing them to be ten thousand times less than the minimum visibile,

they may, notwithstanding, emit light enough to affect the eyes, and so to
cause the luminous appearance aforesaid. This conjecture I send you for
want of something better ****.

FOOTNOTE:

[16] I. Badoin. Editor.

T O M R . P. F . [ 1 7 ] I N N E W P O R T .

On the Saltness of Sea-Water.

London, May 7, 1760.
Sir,
**** It has, indeed, as you observe, been the opinion of some very great
naturalists, that the sea is salt only from the dissolution of mineral or rock-
salt, which its waters happened to meet with. But this opinion takes it for
granted that all water was originally fresh, of which we can have no proof. I
own I am inclined to a different opinion, and rather think all the water on
this globe was originally salt, and that the fresh water we find in springs and
rivers, is the produce of distillation. The sun raises the vapours from the sea,
which form clouds, and fall in rain upon the land, and springs and rivers are
formed of that rain. As to the rock-salt found in mines, I conceive, that
instead of communicating its saltness to the sea, it is itself drawn from the
sea, and that of course the sea is now fresher than it was originally. This is
only another effect of nature's distillery, and might be performed various
ways.
It is evident from the quantities of sea-shells, and the bones and teeth of
fishes found in high lands, that the sea has formerly covered them. Then,
either the sea has been higher than it now is, and has fallen away from those
high lands, or they have been lower than they are, and were lifted up out of
the water to their present height, by some internal mighty force, such as we

still feel some remains of, when whole continents are moved by
earthquakes. In either case it may be supposed that large hollows or valleys
among hills, might be left filled with sea-water, which evaporating, and the
fluid part drying away in a course of years, would leave the salt covering
the bottom; and that salt coming afterwards to be covered with earth, from
the neighbouring hills, could only be found by digging through that earth.
Or, as we know from their effects, that there are deep fiery caverns under
the earth, and even under the sea, if at any time the sea leaks into any of
them, the fluid parts of the water must evaporate from that heat, and pass
off through some volcano, while the salt remains, and by degrees, and
continual acretion, becomes a great mass. Thus the cavern may at length be
filled, and the volcano connected with it cease burning, as many it is said
have done; and future miners, penetrating such cavern, find what we call a
salt-mine. This is a fancy I had on visiting the salt-mines at Northwich, with
my son. I send you a piece of the rock-salt which he brought up with him
out of the mine. ****
I am, Sir, &c.
B. FRANKLIN.

FOOTNOTE:

[17] Peter Franklin. Editor.

TO MISS STEPHENSON.

On the Effect of Air on the Barometer, and the Benefits derived from the Study of Insects.

Craven Street, June 11, 1760.
'Tis a very sensible question you ask, how the air can affect the
barometer, when its opening appears covered with wood? If indeed it was
so closely covered as to admit of no communication of the outward air to
the surface of the mercury, the change of weight in the air could not

possibly affect it. But the least crevice is sufficient for the purpose; a
pinhole will do the business. And if you could look behind the frame to
which your barometer is fixed, you would certainly find some small
opening.
There are indeed some barometers in which the body of mercury at the
lower end is contained in a close leather bag, and so the air cannot come
into immediate contact with the mercury; yet the same effect is produced.
For the leather being flexible, when the bag is pressed by any additional
weight of air it contracts, and the mercury is forced up into the tube; when
the air becomes lighter, and its pressure less, the weight of the mercury
prevails, and it descends again into the bag.
Your observation on what you have lately read concerning insects is very
just and solid. Superficial minds are apt to despise those who make that part
of the creation their study, as mere triflers; but certainly the world has been
much obliged to them. Under the care and management of man, the labours
of the little silkworm afford employment and subsistence to thousands of
families, and become an immense article of commerce. The bee, too, yields
us its delicious honey, and its wax useful to a multitude of purposes.
Another insect, it is said, produces the cochineal, from whence we have our
rich scarlet dye. The usefulness of the cantharides or Spanish flies, in
medicine, is known to all, and thousands owe their lives to that knowledge.
By human industry and observation, other properties of other insects may
possibly be hereafter discovered, and of equal utility. A thorough
acquaintance with the nature of these little creatures may also enable
mankind to prevent the increase of such as are noxious, or secure us against
the mischiefs they occasion. These things doubtless your books make
mention of: I can only add a particular late instance which I had from a
Swedish gentleman of good credit. In the green timber, intended for ship-
building at the king's yards in that country, a kind of worms were found,
which every year became more numerous and more pernicious, so that the
ships were greatly damaged before they came into use. The king sent
Linnæus, the great naturalist, from Stockholm, to enquire into the affair, and
see if the mischief was capable of any remedy. He found, on examination,
that the worm was produced from a small egg, deposited in the little
roughnesses on the surface of the wood, by a particular kind of fly or beetle;
from whence the worm, as soon as it was hatched, began to eat into the

substance of the wood, and after some time came out again a fly of the
parent kind, and so the species increased. The season in which the fly laid
its eggs, Linnæus knew to be about a fortnight (I think) in the month of
May, and at no other time in the year. He therefore advised, that some days
before that season, all the green timber should be thrown into the water, and
kept under water till the season was over. Which being done by the king's
order, the flies missing their usual nests, could not increase; and the species
was either destroyed or went elsewhere; and the wood was effectually
preserved, for after the first year, it became too dry and hard for their
purpose.
There is, however, a prudent moderation to be used in studies of this
kind. The knowledge of nature may be ornamental, and it may be useful,
but if to attain an eminence in that, we neglect the knowledge and practice
of essential duties, we deserve reprehension. For there is no rank in natural
knowledge of equal dignity and importance with that of being a good
parent, a good child, a good husband, or wife, a good neighbour or friend, a
good subject or citizen, that is, in short, a good christian. Nicholas
Gimcrack, therefore, who neglected the care of his family, to pursue
butterflies, was a just object of ridicule, and we must give him up as fair
game to the satyrist.
Adieu, my dear friend, and believe me ever
Yours affectionately,
B. FRANKLIN.

TO THE SAME.

On the Bristol Waters, and the Tide in Rivers.

London, Sept. 13, 1760.
My dear Friend,
I have your agreeable letter from Bristol, which I take this first leisure
hour to answer, having for some time been much engaged in business.

Your first question, What is the reason the water at this place, though
cold at the spring, becomes warm by pumping? It will be most prudent in
me to forbear attempting to answer, till, by a more circumstantial account,
you assure me of the fact. I own I should expect that operation to warm, not
so much the water pumped, as the person pumping.—The rubbing of dry
solids together has been long observed to produce heat; but the like effect
has never yet, that I have heard, been produced by the mere agitation of
fluids, or friction of fluids with solids. Water in a bottle shook for hours by
a mill-hopper, it is said, discovered no sensible addition of heat. The
production of animal heat by exercise is therefore to be accounted for in
another manner, which I may hereafter endeavour to make you acquainted
with.
This prudence of not attempting to give reasons before one is sure of
facts, I learnt from one of your sex, who, as Selden tells us, being in
company with some gentlemen that were viewing, and considering
something which they called a Chinese shoe, and disputing earnestly about
the manner of wearing it, and how it could possibly be put on; put in her
word, and said modestly, Gentlemen, are you sure it is a shoe?—Should not
that be settled first?
But I shall now endeavour to explain what I said to you about the tide in
rivers, and to that end shall make a figure, which though not very like a
river, may serve to convey my meaning.—Suppose a canal one hundred and
forty miles long, communicating at one end with the sea, and filled
therefore with sea water. I chuse a canal at first, rather than a river, to throw
out of consideration the effects produced by the streams of fresh water from
the land, the inequality in breadth, and the crookedness of courses.

Let A, C, be the head of the canal; C, D, the bottom of it; D, F, the open
mouth of it next the sea. Let the strait pricked line, B, G, represent low
water mark the whole length of the canal, A, F, high water mark:—Now if a
person standing at E, and observing at the time of high water there, that the
canal is quite full at that place up to the line E, should conclude that the
canal is equally full to the same height from end to end, and therefore there
was as much more water come into the canal since it was down at low water
mark, as would be included in the oblong space A, B, G, F, he would be
greatly mistaken. For the tide is a wave, and the top of the wave, which
makes high water, as well as every other lower part, is progressive; and it is
high water successively, but not at the same time, in all the several points
between G, F, and A, B.—And in such a length as I have mentioned it is
low water at F, G, and also at A, B, at or near the same time with its being
high water at E; so that the surface of the water in the canal, during that
situation, is properly represented by the curve pricked line B, E, G. And on
the other hand, when it is low water at E, H, it is high water both at F, G,
and at A, B, at or near the same time: and the surface would then be
described by the inverted curve line, A, H, F.
In this view of the case, you will easily see, that there must be very little
more water in the canal at what we call high water, than there is at low
water, those terms not relating to the whole canal at the same time, but
successively to its parts. And if you suppose the canal six times as long, the
case would not vary as to the quantity of water at different times of the tide;
there would only be six waves in the canal at the same time, instead of one,
and the hollows in the water would be equal to the hills.
That this is not mere theory, but conformable to fact, we know by our
long rivers in America. The Delaware, on which Philadelphia stands, is in
this particular similar to the canal I have supposed of one wave: for when it
is high water at the Capes or mouth of the river, it is also high water at
Philadelphia, which stands about one hundred and forty miles from the sea;
and there is at the same time a low water in the middle between the two
high waters; where, when it comes to be high water, it is at the same time
low water at the Capes and at Philadelphia. And the longer rivers have some
a wave and half, some two, three, or four waves, according to their length.
In the shorter rivers of this island, one may see the same thing in part: for
instance, it is high water at Gravesend an hour before it is high water at

London Bridge; and twenty miles below Gravesend an hour before it is high
water at Gravesend. Therefore at the time of high water at Gravesend the
top of the wave is there, and the water is then not so high by some feet
where the top of the wave was an hour before, or where it will be an hour
after, as it is just then at Gravesend.
Now we are not to suppose, that because the swell or top of the wave
runs at the rate of twenty miles an hour, that therefore the current, or water
itself of which the wave is composed, runs at that rate. Far from it. To
conceive this motion of a wave, make a small experiment or two. Fasten
one end of a cord in a window near the top of a house, and let the other end
come down to the ground; take this end in your hand, and you may, by a
sudden motion, occasion a wave in the cord that will run quite up to the
window; but though the wave is progressive from your hand to the window,
the parts of the rope do not proceed with the wave, but remain where they
were, except only that kind of motion that produces the wave. So if you
throw a stone into a pond of water when the surface is still and smooth, you
will see a circular wave proceed from the stone as its centre, quite to the
sides of the pond; but the water does not proceed with the wave, it only
rises and falls to form it in the different parts of its course; and the waves
that follow the first, all make use of the same water with their predecessors.
But a wave in water is not indeed in all circumstances exactly like that in
a cord; for water being a fluid, and gravitating to the earth, it naturally runs
from a higher place to a lower; therefore the parts of the wave in water do
actually run a little both ways from its top towards its lower sides, which
the parts of the wave in the cord cannot do. Thus, when it is high and
standing water at Gravesend, the water twenty miles below has been
running ebb, or towards the sea for an hour, or ever since it was high water
there; but the water at London Bridge will run flood, or from the sea yet
another hour, till it is high water, or the top of the wave arrives at that
bridge, and then it will have run ebb an hour at Gravesend, &c. &c. Now
this motion of the water, occasioned only by its gravity, or tendency to run
from a higher place to a lower, is by no means so swift as the motion of the
wave. It scarce exceeds perhaps two miles in an hour.
If it went as the wave does twenty miles an hour, no ships could ride at
anchor in such a stream, nor boats row against it.

In common speech, indeed, this current of the water both ways from the
top of the wave is called the tide; thus we say, the tide runs strong, the tide
runs at the rate of one, two, or three miles an hour, &c. and when we are at
a part of the river behind the top of the wave, and find the water lower than
high-water mark, and running towards the sea, we say, the tide runs ebb;
and when we are before the top of the wave, and find the water higher than
low-water mark, and running from the sea, we say, the tide runs flood; but
these expressions are only locally proper; for a tide, strictly speaking, is one
whole wave, including all its parts higher and lower, and these waves
succeed one another about twice in twenty-four hours.
This motion of the water, occasioned by its gravity, will explain to you
why the water near the mouths of rivers may be salter at high water than at
low. Some of the salt-water, as the tide wave enters the river, runs from its
top and fore side, and mixes with the fresh, and also pushes it back up the
river.
Supposing that the water commonly runs during the flood at the rate of
two miles in an hour, and that the flood runs five hours, you see that it can
bring at most into our canal only a quantity of water equal to the space
included in the breadth of the canal, ten miles of its length, and the depth
between low and high-water mark; which is but a fourteenth part of what
would be necessary to fill all the space between low and high-water mark,
for one hundred and forty miles, the whole length of the canal.
And indeed such a quantity of water as would fill that whole space, to run
in and out every tide, must create so outrageous a current, as would do
infinite damage to the shores, shipping, &c. and make the navigation of a
river almost impracticable.
I have made this letter longer than I intended, and therefore reserve for
another what I have further to say on the subject of tides and rivers. I shall
now only add, that I have not been exact in the numbers, because I would
avoid perplexing you with minute calculations, my design at present being
chiefly to give you distinct and clear ideas of the first principles.
After writing six folio pages of philosophy to a young girl, is it necessary
to finish such a letter with a compliment?—Is not such a letter of itself a
compliment?—Does it not say, she has a mind thirsty after knowledge, and
capable of receiving it; and that the most agreeable things one can write to

her are those that tend to the improvement of her understanding?—It does
indeed say all this, but then it is still no compliment; it is no more than plain
honest truth, which is not the character of a compliment. So if I would
finish my letter in the mode, I should yet add some thing that means
nothing, and is merely civil and polite. But being naturally aukward at every
circumstance of ceremony, I shall not attempt it. I had rather conclude
abruptly with what pleases me more than any compliment can please you,
that I am allowed to subscribe myself
Your affectionate friend,
B. FRANKLIN.

TO THE SAME.

On the same Subject.

Craven-street, Monday, March 30, 1761.
My dear Friend,
Supposing the fact, that the water of the well at Bristol is warmer after
sometime pumping, I think your manner of accounting for that increased
warmth very ingenious and probable. It did not occur to me, and therefore I
doubted of the fact.
You are, I think quite right in your opinion, that the rising of the tides in
rivers is not owing to the immediate influence of the moon on the rivers. It
is rather a subsequent effect of the influence of the moon on the sea, and
does not make its appearance in some rivers till the moon has long passed
by. I have not expressed myself clearly if you have understood me to mean
otherwise. You know I have mentioned it as a fact, that there are in some
rivers several tides all existing at the same time; that is, two, three, or more,
high-waters, and as many low-waters, in different parts of the same river,
which cannot possibly be all effects of the moon's immediate action on that
river; but they may be subsequent effects of her action on the sea.
In the enclosed paper you will find my sentiments on several points
relating to the air, and the evaporation of water. It is Mr. Collinson's copy,

who took it from one I sent through his hands to a correspondent in France
some years since; I have, as he desired me, corrected the mistakes he made
in transcribing, and must return it to him; but if you think it worth while,
you may take a copy of it: I would have saved you any trouble of that kind,
but had not time.
Some day in the next or the following week, I purpose to have the
pleasure of seeing you at Wanstead: I shall accompany your good mamma
thither, and stay till the next morning, if it may be done without
incommoding your family too much.—We may then discourse any points in
that paper that do not seem clear to you; and taking a walk to lord Tilney's
ponds, make a few experiments there to explain the nature of the tides more
fully. In the mean time, believe me to be, with the highest esteem and
regard, your sincerely affectionate friend,
B. FRANKLIN.

TO THE SAME.

Salt-Water rendered fresh by Distillation.—Method of relieving Thirst by Sea-Water.

Craven-street, August 10, 1761.
We are to set out this week for Holland, where we may possibly spend a
month, but purpose to be at home again before the coronation. I could not
go without taking leave of you by a line at least, when I am so many letters
in your debt.
In yours of May 19, which I have before me, you speak of the ease with
which salt water may be made fresh by distillation, supposing it to be, as I
had said, that in evaporation the air would take up water but not the salt that
was mixed with it. It is true that distilled sea water will not be salt, but there
are other disagreeable qualities that rise with the water in distillation; which
indeed several besides Dr. Hales have endeavoured by some means to
prevent; but as yet their methods have not been brought much into use.
I have a singular opinion on this subject, which I will venture to
communicate to you, though I doubt you will rank it among my whims. It is
certain that the skin has imbibing as well as discharging pores; witness the
effects of a blistering plaister, &c. I have read that a man, hired by a
physician to stand by way of experiment in the open air naked during a
moist night, weighed near three pounds heavier in the morning. I have often
observed myself, that however thirsty I may have been before going into the
water to swim, I am never long so in the water. These imbibing pores,
however, are very fine, perhaps fine enough in filtering to separate salt from
water; for though I have soaked (by swimming, when a boy) several hours
in the day for several days successively in salt-water, I never found my
blood and juices salted by that means, so as to make me thirsty or feel a salt
taste in my mouth: and it is remarkable, that the flesh of sea fish, though
bred in salt-water, is not salt.—Hence I imagine, that if people at sea,
distressed by thirst when their fresh water is unfortunately spent, would
make bathing-tubs of their empty water-casks, and, filling them with sea-
water, sit in them an hour or two each day, they might be greatly relieved.
Perhaps keeping their clothes constantly wet might have an almost equal
effect; and this without danger of catching cold. Men do not catch cold by

wet cloaths at sea. Damp, but not wet linen may possibly give colds; but no
one catches cold by bathing, and no clothes can be wetter than water itself.
Why damp clothes should then occasion colds, is a curious question, the
discussion of which I reserve for a future letter, or some future
conversation.
Adieu, my little philosopher. Present my respectful compliments to the
good ladies your aunts, and to miss Pitt; and believe me ever
Your affectionate friend,
And humble Servant,
B. FRANKLIN.

TO THE SAME.

Tendency of Rivers to the Sea.—Effect of the Sun's Rays on Cloths of different Colours.

Sept. 20, 1761.
My dear Friend,
It is, as you observed in our late conversation, a very general opinion,
that all rivers run into the sea, or deposite their waters there. 'Tis a kind of
audacity to call such general opinions in question, and may subject one to
censure. But we must hazard something in what we think the cause of truth:
and if we propose our objections modestly, we shall, though mistaken,
deserve a censure less severe, than when we are both mistaken and insolent.
That some rivers run into the sea is beyond a doubt: such, for instance,
are the Amazons, and I think the Oronoko and the Mississippi. The proof is,
that their waters are fresh quite to the sea, and out to some distance from the
land. Our question is, whether the fresh waters of those rivers whose beds
are filled with salt water to a considerable distance up from the sea (as the
Thames, the Delaware, and the rivers that communicate with Chesapeak-
bay in Virginia) do ever arrive at the sea? And as I suspect they do not, I am
now to acquaint you with my reasons; or, if they are not allowed to be
reasons, my conceptions at least, of this matter.

The common supply of rivers is from springs, which draw their origin
from rain that has soaked into the earth. The union of a number of springs
forms a river. The waters as they run, exposed to the sun, air, and wind, are
continually evaporating. Hence in travelling one may often see where a
river runs, by a long blueish mist over it, though we are at such a distance
as not to see the river itself. The quantity of this evaporation is greater or
less, in proportion to the surface exposed by the same quantity of water to
those causes of evaporation. While the river runs in a narrow confined
channel in the upper hilly country, only a small surface is exposed; a greater
as the river widens. Now if a river ends in a lake, as some do, whereby its
waters are spread so wide as that the evaporation is equal to the sum of all
its springs, that lake will never overflow:—And if instead of ending in a
lake, it was drawn into greater length as a river, so as to expose a surface
equal in the whole to that lake, the evaporation would be equal, and such
river would end as a canal; when the ignorant might suppose, as they
actually do in such cases, that the river loses itself by running under ground,
whereas in truth it has run up into the air.
Now, many rivers that are open to the sea widen much before they arrive
at it, not merely by the additional waters they receive, but by having their
course stopped by the opposing flood-tide; by being turned back twice in
twenty-four hours, and by finding broader beds in the low flat countries to
dilate themselves in; hence the evaporation of the fresh water is
proportionably increased; so that in some rivers it may equal the springs of
supply. In such cases, the salt water comes up the river, and meets the fresh
in that part where, if there were a wall or bank of earth across from side to
side, the river would form a lake, fuller indeed at some times than at others,
according to the seasons, but whose evaporation would, one time with
another, be equal to its supply.
When the communication between the two kinds of water is open, this
supposed wall of separation may be conceived as a moveable one, which is
not only pushed some miles higher up the river by every flood tide from the
sea, and carried down again as far by every tide of ebb, but which has even
this space of vibration removed nearer to the sea in wet seasons, when the
springs and brooks in the upper country are augmented by the falling rains,
so as to swell the river, and farther from the sea in dry seasons.

Within a few miles above and below this moveable line of separation, the
different waters mix a little, partly by their motion to and fro, and partly
from the greater specific gravity of the salt water, which inclines it to run
under the fresh, while the fresh water, being lighter, runs over the salt.
Cast your eye on the map of North America, and observe the bay of
Chesapeak in Virginia, mentioned above; you will see, communicating with
it by their mouths, the great rivers Sasquehanah, Potowmack, Rappahanock,
York, and James, besides a number of smaller streams, each as big as the
Thames. It has been proposed by philosophical writers, that to compute how
much water any river discharges into the sea in a given time, we should
measure its depth and swiftness at any part above the tide; as, for the
Thames, at Kingston or Windsor. But can one imagine, that if all the water
of those vast rivers went to the sea, it would not first have pushed the salt
water out of that narrow-mouthed bay, and filled it with fresh?—The
Sasquehanah alone would seem to be sufficient for this, if it were not for
the loss by evaporation. And yet that bay is salt quite up to Annapolis.
As to our other subject, the different degrees of heat imbibed from the
sun's rays by cloths of different colours, since I cannot find the notes of my
experiment to send you, I must give it as well as I can from memory.
But first let me mention an experiment you may easily make yourself.
Walk but a quarter of an hour in your garden when the sun shines, with a
part of your dress white, and a part black; then apply your hand to them
alternately, and you will find a very great difference in their warmth. The
black will be quite hot to the touch, the white still cool.
Another. Try to fire the paper with a burning glass. If it is white, you will
not easily burn it;—but if you bring the focus to a black spot, or upon
letters, written or printed, the paper will immediately be on fire under the
letters.
Thus fullers and dyers find black cloths, of equal thickness with white
ones, and hung out equally wet, dry in the sun much sooner than the white,
being more readily heated by the sun's rays. It is the same before a fire; the
heat of which sooner penetrates black stockings than white ones, and so is
apt sooner to burn a man's shins. Also beer much sooner warms in a black
mug set before the fire, than in a white one, or in a bright silver tankard.

My experiment was this. I took a number of little square pieces of broad
cloth from a taylor's pattern-card, of various colours. There were black,
deep blue, lighter blue, green, purple, red, yellow, white, and other colours,
or shades of colours. I laid them all out upon the snow in a bright sun-shiny
morning. In a few hours (I cannot now be exact as to the time) the black,
being warmed most by the sun, was sunk so low as to be below the stroke
of the sun's rays; the dark blue almost as low, the lighter blue not quite so
much as the dark, the other colours less as they were lighter; and the quite
white remained on the surface of the snow, not having entered it at all.
What signifies philosophy that does not apply to some use?—-May we
not learn from hence, that black clothes are not so fit to wear in a hot sunny
climate or season, as white ones; because in such clothes the body is more
heated by the sun when we walk abroad, and are at the same time heated by
the exercise, which double heat is apt to bring on putrid dangerous fevers?
That soldiers and seamen, who must march and labour in the sun, should in
the East or West Indies have an uniform of white? That summer hats, for
men or women, should be white, as repelling that heat which gives head-
achs to many, and to some the fatal stroke that the French call the coup de
soleil? That the ladies summer hats, however, should be lined with black, as
not reverberating on their faces those rays which are reflected upwards from
the earth or water? That the putting a white cap of paper or linen within the
crown of a black hat, as some do, will not keep out the heat, though it
would if placed without. That fruit-walls being blacked may receive so
much heat from the sun in the day-time, as to continue warm in some
degree through the night, and thereby preserve the fruit from frosts, or
forward its growth?—with sundry other particulars of less or greater
importance, that will occur from time to time to attentive minds?—I am,
Yours affectionately,
B. FRANKLIN.

TO MR. HOPKINSON.

On the Vis Inertiæ of Matter.

Philadelphia, 1748.
Sir,
According to my promise, I send you in writing my observations on your
book[18]: you will be the better able to consider them; which I desire you to
do at your leisure, and to set me right where I am wrong.
I stumble at the threshold of the building, and therefore have not read
farther. The author's vis inertiæ essential to matter, upon which the whole
work is founded, I have not been able to comprehend. And I do not think he
demonstrates at all clearly (at least to me he does not) that there is really
such a property in matter.
He says, No. 2. "Let a given body or mass of matter be called a, and let
any given celerity be called c. That celerity doubled, tripled, &c. or halved,
thirded, &c. will be 2 c, 3 c, &c. or ½ c, ⅓ c, &c. respectively: also the body
doubled, tripled, or halved, thirded, will be 2 a, 3 a, or ½ a, ⅓ a,
respectively." Thus far is clear.—But he adds, "Now to move the body a
with the celerity c, requires a certain force to be impressed upon it; and to
move it with a celerity as 2 c, requires twice that force to be impressed upon
it, &c." Here I suspect some mistake creeps in by the author's not
distinguishing between a great force applied at once, or a small one
continually applied, to a mass of matter, in order to move it. I think it is
generally allowed by the philosophers, and, for aught we know, is certainly
true, that there is no mass of matter, how great soever, but may be moved by
any force how small soever (taking friction out of the question) and this
small force continued, will in time bring the mass to move with any
velocity whatsoever.—Our author himself seems to allow this towards the
end of the same No. 2. when he is subdividing his celerities and forces: for
as in continuing the division to eternity by his method of ½ c, ⅓ c, ¼ c, ⅕ c,
&c. you can never come to a fraction of velocity that is equal to 0 c, or no
celerity at all; so dividing the force in the same manner, you can never come
to a fraction of force that will not produce an equal fraction of celerity.—
Where then is the mighty vis inertiæ, and what is its strength; when the
greatest assignable mass of matter will give way to, or be moved by the
least assignable force? Suppose two globes, equal to the sun and to one
another, exactly equipoised in Jove's balance; suppose no friction in the
centre of motion, in the beam or elsewhere: if a musketo then were to light

on one of them, would he not give motion to them both, causing one to
descend and the other to rise? If it is objected, that the force of gravity helps
one globe to descend, I answer, the same force opposes the other's rising:
here is an equality that leaves the whole motion to be produced by the
musketo, without whom those globes would not be moved at all.—What
then does vis inertiæ do in this case? and what other effect could we expect
if there were no such thing? Surely if it were any thing more than a
phantom, there might be enough of it in such vast bodies to annihilate, by
its opposition to motion, so trifling a force?
Our author would have reasoned more clearly, I think, if, as he has used
the letter a for a certain quantity of matter, and c for a certain quantity of
celerity, he had employed one letter more, and put f perhaps, for a certain
quantity of force. This let us suppose to be done; and then as it is a maxim
that the force of bodies in motion is equal to the quantity of matter
multiplied by the celerity, (or f = c X a); and as the force received by and
subsisting in matter, when it is put in motion, can never exceed the force
given; so if, f moves a with c, there must needs be required 2 f to move a
with 2 c; for a moving with 2 c would have a force equal to 2 f, which it
could not receive from 1 f; and this, not because there is such a thing as vis
inertiæ, for the case would be the same if that had no existence; but because
nothing can give more than it has, if 1 f can to 1 a give 1 c, which is the
same thing as giving it 1 f; (i. e. if force applied to matter at rest, can put it
in motion, and give it equal force) where then is vis inertiæ? If it existed at
all in matter, should we not find the quantity of its resistance subtracted
from the force given?
In No. 4. our author goes on and says, "the body a requires a certain force
to be impressed on it to be moved with a celerity as c, or such a force is
necessary; and therefore makes a certain resistance, &c. A body as 2 a
requires twice that force to be moved with the same celerity, or it makes
twice that resistance; and so on."—This I think is not true; but that the body
2 a moved by the force 1 f (though the eye may judge otherwise of it) does
really move with the same celerity as it did when impelled by the same
force; for 2 a is compounded of 1 a+1 a: and if each of the 1 a's or each part
of the compound were made to move with 1 c (as they might be by 2 f) then
the whole would move with 2 c, and not with 1 c, as our author supposes.
But 1 f applied to 2 a, makes each a move with ½ c; and so the whole

moves with 1 c; exactly the same as 1 a was made to do by 1 f before. What
is equal celerity but a measuring the same space by moving bodies in the
same time?—Now if 1 a impelled by 1 f measures 100 yards in a minute;
and in 2 a impelled by 1 f, each a measures 50 yards in a minute, which
added make 100; are not the celerities as the forces equal? and since force
and celerity in the same quantity of matter are always in proportion to each
other, why should we, when the quantity of matter is doubled, allow the
force to continue unimpaired, and yet suppose one half of the celerity to be
lost?—I wonder the more at our author's mistake in this point, since in the
same number I find him observing: "We may easily conceive that a body as
3 a, 4 a, &c. would make 3 or 4 bodies equal to once a, each of which
would require once the first force to be moved with the celerity c." If then
in 3 a, each a requires once the first force f to be moved with the celerity c,
would not each move with the force f and celerity c; and consequently the
whole be 3 a moving with 3 f and 3 c? After so distinct an observation, how
could he miss of the consequence, and imagine that 1 c and 3 c were the
same? Thus as our author's abatement of celerity in the case of 2 a moved
by 1 f is imaginary, so must be his additional resistance.—And here again, I
am at a loss to discover any effect of the vis inertiæ.
In No. 6, he tells us, "that all this is likewise certain when taken the
contrary way, viz. from motion to rest; for the body a moving with a certain
velocity, as c, requires a certain degree of force or resistance to stop that
motion, &c. &c." that is, in other words, equal force is necessary to destroy
force. It may be so. But how does that discover a vis inertiæ? would not the
effect be the same if there were no such thing? A force 1 f strikes a body 1
a, and moves it with the celerity 1 c, i. e. with the force 1 f: It requires, even
according to our author, only an opposing 1 f to stop it. But ought it not (if
there were a vis inertiæ) to have not only the force 1 f, but an additional
force equal to the force of vis inertiæ, that obstinate power by which a body
endeavours with all its might to continue in its present state, whether of
motion or rest? I say, ought there not to be an opposing force equal to the
sum of these?—The truth however is, that there is no body, how large
soever, moving with any velocity, how great soever, but may be stopped by
any opposing force, how small soever, continually applied. At least all our
modern philosophers agree to tell us so.

Let me turn the thing in what light I please, I cannot discover the vis
inertiæ, nor any effect of it. It is allowed by all, that a body 1 a moving with
a velocity 1 c, and a force 1 f striking another body 1 a at rest, they will
afterwards move on together, each with ½ c and ½ f; which, as I said before,
is equal in the whole to 1 c and 1 f. If vis inertiæ, as in this case, neither
abates the force nor the velocity of bodies, what does it, or how does it
discover itself?
I imagine I may venture to conclude my observations on this piece,
almost in the words of the author; that if the doctrines of the immateriality
of the soul and the existence of God and of divine providence are
demonstrable from no plainer principles, the deist [i.e. theist] has a
desperate cause in hand. I oppose my theist to his atheist, because I think
they are diametrically opposite; and not near of kin, as Mr. Whitfield seems
to suppose; where (in his journal) he tells us, "M. B. was a deist, I had
almost said an atheist;" that is, chalk, I had almost said charcoal.
The din of the market[19] increases upon me; and that, with frequent
interruptions, has, I find, made me say some things twice over; and, I
suppose, forget some others I intended to say. It has, however, one good
effect, as it obliges me to come to the relief of your patience with
Your humble servant,
B. FRANKLIN.

FOOTNOTES:

[18] Baxter's Inquiry into the Nature of the Human Soul. B. V.
[19] Philadelphia market, in which Dr. Franklin lived. B. V.

T O J O H N P R I N G L E , M . D . A N D F. R . S .

On the different Strata of the Earth.

Craven-Street, Jan. 6, 1758.

Sir,
I return you Mr. Mitchell's paper on the strata of the earth[20] with thanks.
The reading of it, and perusal of the draft that accompanies it, have
reconciled me to those convulsions which all naturalists agree this globe has
suffered. Had the different strata of clay, gravel, marble, coals, lime-stone,
sand, minerals, &c. continued to lie level, one under the other, as they may
be supposed to have done before those convulsions, we should have had the
use only of a few of the uppermost of the strata, the others lying too deep
and too difficult to be come at; but the shell of the earth being broke, and
the fragments thrown into this oblique position, the disjointed ends of a
great number of strata of different kinds are brought up to day, and a great
variety of useful materials put into our power, which would otherwise have
remained eternally concealed from us. So that what has been usually looked
upon as a ruin suffered by this part of the universe, was, in reality, only a
preparation, or means of rendering the earth more fit for use, more capable
of being to mankind a convenient and comfortable habitation.
I am, Sir, with great esteem, yours, &c.
B. FRANKLIN.

FOOTNOTE:

[20] See this paper afterwards printed in the Philosophical Transactions.

T O T H E A B B E S O U L AV I E .

Occasioned by his sending me some notes he had taken of what I had said to him in
conversation on the Theory of the Earth. I wrote it to set him right in some points wherein
he had mistaken my meaning.[21]

Passy, September 22, 1782.
Sir,

I return the papers with some corrections. I did not find coal mines under
the calcareous rock in Derbyshire. I only remarked, that at the lowest part of
that rocky mountain which was in sight, there were oyster shells mixed in
the stone; and part of the high county of Derby being probably as much
above the level of the sea, as the coal mines of Whitehaven were below it,
seemed a proof, that there had been a great bouleversement in the surface of
that island, some part of it having been depressed under the sea, and other
parts, which had been under it, being raised above it. Such changes in the
superficial parts of the globe, seemed to me unlikely to happen, if the earth
were solid to the centre. I therefore imagined, that the internal parts might
be a fluid more dense, and of greater specific gravity than any of the solids
we are acquainted with, which therefore might swim in or upon that fluid.
Thus the surface of the globe would be a shell, capable of being broken and
disordered by the violent movements of the fluid on which it rested. And as
air has been compressed by art so as to be twice as dense as water, in which
case, if such air and water could be contained in a strong glass vessel, the
air would be seen to take the lowest place, and the water to float above and
upon it; and as we know not yet the degree of density to which air may be
compressed, and M. Amontons calculated, that its density increasing as it
approached the centre, in the same proportion as above the surface, it would
at the depth of [ ] leagues, be heavier than gold, possibly the dense fluid
occupying the internal parts of the globe might be air compressed. And as
the force of expansion in dense air when heated is in proportion to its
density, this central air might afford another agent to move the surface, as
well as be of use in keeping alive the subterraneous fires; though, as you
observe, the sudden rarefaction of water coming into contact without those
fires, may also be an agent sufficiently strong for that purpose, when acting
between the incumbent earth and the fluid on which it rests.
If one might indulge imagination in supposing how such a globe was
formed, I should conceive, that all the elements in separate particles being
originally mixed in confusion, and occupying a great space, they would (as
soon as the almighty fiat ordained gravity, or the mutual attraction of certain
parts, and the mutual repulsion of others, to exist) all move to their common
centre: that the air being a fluid whose parts repel each other, though drawn
to the common centre by their gravity, would be densest towards the centre,
and rarer as more remote; consequently all matters lighter than the central
parts of that air, and immersed in it, would recede from the centre, and rise

till they arrived at that region of the air which was of the same specific
gravity with themselves, where they would rest; while other matter, mixed
with the lighter air, would descend, and the two meeting would form the
shell of the first earth, leaving the upper atmosphere nearly clear. The
original movement of the parts towards their common centre would
naturally form a whirl there; which would continue upon the turning of the
new-formed globe upon its axis, and the greatest diameter of the shell
would be in its equator. If by any accident afterwards the axis should be
changed, the dense internal fluid, by altering its form, must burst the shell,
and throw all its substance into the confusion in which we find it. I will not
trouble you at present with my fancies concerning the manner of forming
the rest of our system. Superior beings smile at our theories, and at our
presumption in making them. I will just mention, that your observation of
the ferruginous nature of the lava which is thrown out from the depths of
our volcanoes, gave me great pleasure. It has long been a supposition of
mine, that the iron contained in the surface of the globe has made it capable
of becoming, as it is, a great magnet; that the fluid of magnetism perhaps
exists in all space; so that there is a magnetical north and south of the
universe, as well as of this globe, and that if it were possible for a man to
fly from star to star, he might govern his course by the compass; that it was
by the power of this general magnetism this globe became a particular
magnet. In soft or hot iron the fluid of magnetism is naturally diffused
equally; when within the influence of the magnet it is drawn to one end of
the iron, made denser there and rarer at the other. While the iron continues
soft and hot, it is only a temporary magnet; if it cools or grows hard in that
situation, it becomes a permanent one, the magnetic fluid not easily
resuming its equilibrium. Perhaps it may be owing to the permanent
magnetism of this globe, which it had not at first, that its axis is at present
kept parallel to itself, and not liable to the changes it formerly suffered,
which occasioned the rupture of its shell, the submersions and emersions of
its lands and the confusion of its seasons. The present polar and equatorial
diameters differing from each other near ten leagues, it is easy to conceive,
in case some power should shift the axis gradually, and place it in the
present equator, and make the new equator pass through the present poles,
what a sinking of the waters would happen in the present equatorial regions,
and what a rising in the present polar regions; so that vast tracts would be
discovered, that now are under water, and others covered, that are now dry,

the water rising and sinking in the different extremes near five leagues.
Such an operation as this possibly occasioned much of Europe, and among
the rest this Mountain of Passy on which I live, and which is composed of
limestone, rock and sea-shells, to be abandoned by the sea, and to change
its ancient climate, which seems to have been a hot one. The globe being
now become a perfect magnet, we are, perhaps, safe from any change of its
axis. But we are still subject to the accidents on the surface, which are
occasioned by a wave in the internal ponderous fluid; and such a wave is
producible by the sudden violent explosion you mention, happening from
the junction of water and fire under the earth, which not only lifts the
incumbent earth that is over the explosion, but impressing with the same
force the fluid under it, creates a wave, that may run a thousand leagues,
lifting, and thereby shaking, successively, all the countries under which it
passes. I know not, whether I have expressed myself so clearly, as not to get
out of your sight in these reveries. It they occasion any new enquiries, and
produce a better hypothesis, they will not be quite useless. You see I have
given a loose to imagination; but I approve much more your method of
philosophising, which proceeds upon actual observation, makes a collection
of facts, and concludes no farther than those facts will warrant. In my
present circumstances, that mode of studying the nature of the globe is out
of my power, and therefore I have permitted myself to wander a little in the
wilds of fancy. With great esteem,
I have the honour to be, Sir, &c.
BENJ. FRANKLIN.

P. S. I have heard, that chymists can by their art decompose stone and
wood, extracting a considerable quantity of water from the one, and air
from the other. It seems natural to conclude from this, that water and air
were ingredients in their original composition: for men cannot make new
matter of any kind. In the same manner may we not suppose, that when we
consume combustibles of all kinds, and produce heat or light, we do not
create that heat or light; but only decompose a substance, which received it
originally as a part of its composition? Heat may be thus considered as
originally in a fluid state; but, attracted by organized bodies in their growth,
becomes a part of the solid. Besides this, I can conceive, that in the first

assemblage of the particles of which this earth is composed, each brought
its portion of the loose heat that had been connected with it, and the whole,
when pressed together, produced the internal fire that still subsists.

FOOTNOTE:

[21] In an American periodical publication, this paper is said to have been so
endorsed in Dr. Franklin's hand. We extract the paper itself, from the
Transactions of the American Philosophical Society, where it was read Nov. 21,
1788. The two papers that follow it are from the same work, and were read in the
Society the preceding day, and the other Jan. 15, 1790. Editor.

T O D AV I D R I T T E N H O U S E , E S Q .

New and curious Theory of Light and Heat.

[No date.]

Universal space, as far as we know of it, seems to be filled with a subtle
fluid, whose motion, or vibration, is called light.
This fluid may possibly be the same with that, which, being attracted by,
and entering into other more solid matter, dilates the substance by
separating the constituent particles, and so rendering some solids fluid, and
maintaining the fluidity of others; of which fluid, when our bodies are
totally deprived, they are said to be frozen; when they have a proper
quantity, they are in health, and fit to perform all their functions; it is then
called natural heat; when too much, it is called fever; and when forced into
the body in too great a quantity from without, it gives pain, by separating
and destroying the flesh, and is then called burning, and the fluid so
entering and acting is called fire.
While organised bodies, animal or vegetable, are augmenting in growth,
or are supplying their continual waste, is not this done by attracting and
consolidating this fluid called fire, so as to form of it a part of their
substance? And is it not a separation of the parts of such substance, which,
dissolving its solid state, sets that subtle fluid at liberty, when it again
makes its appearance as fire?
For the power of man relative to matter, seems limited to the separating
or mixing the various kinds of it, or changing its form and appearance by
different compositions of it; but does not extend to the making or creating
new matter, or annihilating the old. Thus, if fire be an original element or
kind of matter, its quantity is fixed and permanent in the universe. We
cannot destroy any part of it, or make addition to it; we can only separate it
from that which confines it, and so set it at liberty; as when we put wood in
a situation to be burnt, or transfer it from one solid to another, as when we
make lime by burning stone, a part of the fire dislodged in the fuel being
left in the stone. May not this fluid, when at liberty, be capable of

penetrating and entering into all bodies, organised or not, quitting easily in
totality those not organised, and quitting easily in part those which are; the
part assumed and fixed remaining till the body is dissolved?
Is it not this fluid which keeps asunder the particles of air, permitting
them to approach, or separating them more, in proportion as its quantity is
diminished or augmented?
Is it not the greater gravity of the particles of air, which forces the
particles of this fluid to mount with the matters to which it is attached, as
smoke or vapour?
Does it not seem to have a greater affinity with water, since it will quit a
solid to unite with that fluid, and go off with it in vapour, leaving the solid
cold to the touch, and the degree measurable by the thermometer?
The vapour rises attached to this fluid, but at a certain height they
separate, and the vapour descends in rain, retaining but little of it, in snow
or hail less. What becomes of that fluid? Does it rise above our atmosphere,
and mix with the universal mass of the same kind?
Or does a spherical stratum of it, denser, as less mixed with air, attracted
by this globe, and repelled or pushed up only to a certain height from its
surface, by the greater weight of air, remain there surrounding the globe,
and proceeding with it round the sun?
In such case, as there may be a continuity or communication of this fluid
through the air quite down to the earth, is it not by the vibrations given to it,
by the sun, that light appears to us? And may it not be, that every one of the
infinitely small vibrations, striking common matter with a certain force,
enters its substance, is held there by attraction, and augmented by
succeeding vibrations, till the matter has received as much as their force can
drive into it?
Is it not thus, that the surface of this globe is continually heated by such
repeated vibrations in the day, and cooled by the escape of the heat when
those vibrations are discontinued in the night, or intercepted and reflected
by clouds?
Is it not thus, that fire is amassed and makes the greatest part of the
substance of combustible bodies?

Perhaps, when this globe was first formed, and its original particles took
their place at certain distances from the centre, in proportion to their greater
or less gravity, the fluid fire, attracted towards that centre, might in great
part be obliged, as lightest, to take place above the rest, and thus form the
sphere of fire above supposed, which would afterwards be continually
diminishing by the substance it afforded to organised bodies, and the
quantity restored to it again, by the burning or other separating of the parts
of those bodies.
Is not the natural heat of animals thus produced, by separating in
digestion the parts of food, and setting their fire at liberty?
Is it not this sphere of fire which kindles the wandering globes that
sometimes pass through it in our course round the sun, have their surface
kindled by it, and burst when their included air is greatly rarefied by the
heat on their burning surfaces?
May it not have been from such considerations that the ancient
philosophers supposed a sphere of fire to exist above the air of our
atmosphere?
B. FRANKLIN.

TO MR. BODOIN.

Queries and Conjectures relating to Magnetism and the Theory of the Earth.

[No date.]

Dear Sir,
I received your favours by Messrs. Gore, Hilliard, and Lee, with whose
conversation I was much pleased, and wished for more of it; but their stay
with us was too short. Whenever you recommend any of your friends to me,
you oblige me.
I want to know whether your Philosophical Society received the second
volume of our Transactions. I sent it, but never heard of its arriving. If it
miscarried, I will send another. Has your Society among its books the
French work Sur les Arts, et les Metiers? It is voluminous, well executed,

and may be useful in our country. I have bequeathed it them in my will; but
if they have it already, I will substitute something else.
Our ancient correspondence used to have something philosophical in it.
As you are now more free from public cares, and I expect to be so in a few
months, why may we not resume that kind of correspondence? Our much
regretted friend Winthrop once made me the compliment, that I was good at
starting game for philosophers, let me try if I can start a little for you.
Has the question, how came the earth by its magnetism, ever been
considered?
Is it likely that iron ore immediately existed when this globe was first
formed; or may it not rather be supposed a gradual production of time?
If the earth is at present magnetical, in virtue of the masses of iron ore
contained in it, might not some ages pass before it had magnetic polarity?
Since iron ore may exist without that polarity, and by being placed in
certain circumstances may obtain it, from an external cause, is it not
possible that the earth received its magnetism from some such cause?
In short, may not a magnetic power exist throughout our system, perhaps
through all systems, so that if men could make a voyage in the starry
regions, a compass might be of use? And may not such universal
magnetism, with its uniform direction, be serviceable in keeping the diurnal
revolution of a planet more steady to the same axis?
Lastly, as the poles of magnets may be changed by the presence of
stronger magnets, might not, in ancient times, the near passing of some
large comet of greater magnetic power than this globe of ours have been a
means of changing its poles, and thereby wrecking and deranging its
surface, placing in different regions the effect of centrifugal force, so as to
raise the waters of the sea in some, while they were depressed in others?
Let me add another question or two, not relating indeed to magnetism,
but, however, to the theory of the earth.
Is not the finding of great quantities of shells and bones of animals
(natural to hot climates) in the cold ones of our present world, some proof
that its poles have been changed? Is not the supposition that the poles have
been changed, the easiest way of accounting for the deluge, by getting rid of

the old difficulty how to dispose of its waters after it was over? Since if the
poles were again to be changed, and placed in the present equator, the sea
would fall there about fifteen miles in height, and rise as much in the
present polar regions; and the effect would be proportionable if the new
poles were placed any where between the present and the equator.
Does not the apparent wreck of the surface of this globe, thrown up into
long ridges of mountains, with strata in various positions, make it probable,
that its internal mass is a fluid; but a fluid so dense as to float the heaviest
of our substances? Do we know the limit of condensation air is capable of?
Supposing it to grow denser within the surface, in the same proportion
nearly as it does without, at what depth may it be equal in density with
gold?
Can we easily conceive how the strata of the earth could have been so
deranged, if it had not been a mere shell supported by a heavier fluid?
Would not such a supposed internal fluid globe be immediately sensible of a
change in the situation of the earth's axis, alter its form, and thereby burst
the shell, and throw up parts of it above the rest? As, if we would alter the
position of the fluid contained in the shell of an egg, and place its longest
diameter where the shortest now is, the shell must break; but would be
much harder to break; if the whole internal substance were as solid and hard
as the shell.
Might not a wave, by any means raised in this supposed internal ocean of
extremely dense fluid, raise in some degree, as it passes, the present shell of
incumbent earth, and break it in some places, as in earthquakes? And may
not the progress of such wave, and the disorders it occasions among the
solids of the shell, account for the rumbling sound being first heard at a
distance, augmenting as it approaches, and gradually dying away as it
proceeds? A circumstance observed by the inhabitants of South America in
their last great earthquake, that noise coming from a place, some degrees
north of Lima, and being traced by enquiry quite down to Buenos Ayres,
proceeded regularly from north to south at the rate of [ ] leagues per
minute, as I was informed by a very ingenious Peruvian whom I met with at
Paris.
B. FRANKLIN.

TO M. DUBOURG.

On the Nature of Sea Coal.[22]

**** I am persuaded, as well as you, that the sea coal has a vegetable
origin, and that it has been formed near the surface of the earth; but as
preceding convulsions of nature had served to bring it very deep in many
places, and covered it with many different strata, we are indebted to
subsequent convulsions for having brought within our view the extremities
of its veins, so as to lead us to penetrate the earth in search of it. I visited
last summer a large coal-mine at Whitehaven, in Cumberland; and in
following the vein and descending by degrees towards the sea, I penetrated
below the ocean, where the level of its surface was more than eight hundred
fathom above my head, and the miners assured me, that their works
extended some miles beyond the place where I then was, continually and
gradually descending under the sea. The slate, which forms the roof of this
coal mine, is impressed in many places with the figures of leaves and
branches of fern, which undoubtedly grew at the surface when the slate was
in the state of sand on the banks of the sea. Thus it appears that this vein of
coal has suffered a prodigious settlement. ****
B. FRANKLIN.

FOOTNOTE:

[22] Retranslated from the French edition of Dr. Franklin's works. Editor.

TO DR. PRIESTLEY[23].

Effect of Vegetation on noxious Air.

**** That the vegetable creation should restore the air which is spoiled
by the animal part of it, looks like a rational system, and seems to be of a

piece with the rest. Thus fire purifies water all the world over. It purifies it
by distillation, when it raises it in vapours, and lets it fall in rain; and farther
still by filtration, when, keeping it fluid, it suffers that rain to percolate the
earth. We knew before, that putrid animal substances were converted into
sweet vegetables, when mixed with the earth, and applied as manure; and
now, it seems, that the same putrid substances, mixed with the air, have a
similar effect. The strong thriving state of your mint, in putrid air, seems to
shew, that the air is mended by taking something from it, and not by adding
to it. I hope this will give some check to the rage of destroying trees that
grow near houses, which has accompanied our late improvements in
gardening, from an opinion of their being unwholesome. I am certain, from
long observation, that there is nothing unhealthy in the air of woods; for we
Americans have every where our country habitations in the midst of woods,
and no people on earth enjoy better health, or are more prolific. ****
B. FRANKLIN.

FOOTNOTE:

[23] This extract is taken from Dr. Priestley's Experiments on Air, Vol. I. page
94. It was written in answer to a note from Dr. Priestley, informing our author of
the result of certain experiments on some plants which he had seen at Dr.
Priestley's house in a very flourishing state, in jars of highly noxious air. Editor.

TO THE SAME[24].

On the Inflammability of the Surface of certain Rivers in America.

Craven-street, April 10, 1774.
Dear Sir,
In compliance with your request, I have endeavoured to recollect the
circumstances of the American experiments I formerly mentioned to you, of
raising a flame on the surface of some waters there.

When I passed through New Jersey in 1764, I heard it several times
mentioned, that by applying a lighted candle near the surface of some of
their rivers, a sudden flame would catch and spread on the water, continuing
to burn for near half a minute. But the accounts I received were so
imperfect, that I could form no guess at the cause of such an effect, and
rather doubted the truth of it. I had no opportunity of seeing the experiment;
but calling to see a friend who happened to be just returning home from
making it himself, I learned from him the manner of it; which was to choose
a shallow place, where the bottom could be reached by a walking-stick, and
was muddy; the mud was first to be stirred with the stick, and when a
number of small bubbles began to arise from it, the candle was applied. The
flame was so sudden and so strong, that it catched his ruffle and spoiled it,
as I saw. New Jersey having many pine-trees in many parts of it, I then
imagined that something like a volatile oil of turpentine might be mixed
with the waters from a pine-swamp, but this supposition did not quite
satisfy me. I mentioned the fact to some philosophical friends on my return
to England, but it was not much attended to. I suppose I was thought a little
too credulous.
In 1765, the Reverend Dr. Chandler received a letter from Dr. Finley,
President of the College in that province, relating the same experiment. It
was read at the Royal Society, November 21 of that year, but not printed in
the Transactions; perhaps because it was thought too strange to be true, and
some ridicule might be apprehended, if any member should attempt to
repeat it, in order to ascertain, or refute it. The following is a copy of that
account.
"A worthy gentleman, who lives at a few miles distance, informed me,
that in a certain small cove of a mill-pond, near his house, he was surprized
to see the surface of the water blaze like inflamed spirits. I soon after went
to the place, and made the experiment with the same success. The bottom of
the creek was muddy, and when stirred up, so as to cause a considerable
curl on the surface, and a lighted candle held within two or three inches of
it, the whole surface was in a blaze, as instantly as the vapour of warm
inflammable spirits, and continued, when strongly agitated, for the space of
several seconds. It was at first imagined to be peculiar to that place; but
upon trial it was soon found, that such a bottom in other places exhibited

the same phenomenon. The discovery was accidentally made by one
belonging to the mill."
I have tried the experiment twice here in England, but without success.
The first was in a slow running water with a muddy bottom. The second in a
stagnant water at the bottom of a deep ditch. Being some time employed in
stirring this water, I ascribed an intermitting fever, which seized me a few
days after, to my breathing too much of that foul air, which I stirred up from
the bottom, and which I could not avoid while I stooped, endeavouring to
kindle it. The discoveries you have lately made, of the manner in which
inflammable air is in some cases produced, may throw light on this
experiment, and explain its succeeding in some cases, and not in others.
With the highest esteem and respect,
I am, dear Sir, your most obedient humble servant,
B. FRANKLIN.

FOOTNOTE:

[24] From his Experiments on Air, Vol. I. page 321. Editor.

T O D R . P E R C I VA L [ 2 5 ] .

On the different Quantities of Rain which fall at different Heights over the same Ground.

[No date.]
On my return to London I found your favour of the 16th of May (1771). I
wish I could, as you desire, give you a better explanation of the
phenomenon in question, since you seem not quite satisfied with your own;
but I think we want more and a greater variety of experiments, in different
circumstances, to enable us to form a thoroughly satisfactory hypothesis.
Not that I make the least doubt of the facts already related, as I know both
Lord Charles Cavendish, and Dr. Heberden to be very accurate
experimenters: but I wish to know the event of the trials proposed in your
six queries; and also, whether in the same place where the lower vessel
receives nearly twice the quantity of water that is received by the upper, a
third vessel placed at half the height will receive a quantity proportionable.
I will however endeavour to explain to you what occurred to me, when I
first heard of the fact.
I suppose it will be generally allowed, on a little consideration of the
subject, that scarce any drop of water was, when it began to fall from the
clouds, of a magnitude equal to that it has acquired, when it arrives at the
earth; the same of the several pieces of hail; because they are often so large
and so weighty, that we cannot conceive a possibility of their being
suspended in the air, and remaining at rest there, for any time, how small
soever; nor do we conceive any means of forming them so large, before
they set out to fall. It seems then, that each beginning drop, and particle of
hail, receives continual addition in its progress downwards. This may be
several ways: by the union of numbers in their course, so that what was at
first only descending mist, becomes a shower; or by each particle, in its
descent through air that contains a great quantity of dissolved water,
striking against, attaching to itself, and carrying down with it such particles
of that dissolved water, as happen to be in its way; or attracting to itself

such as do not lie directly in its course by its different state with regard
either to common or electric fire; or by all these causes united.
In the first case, by the uniting of numbers, larger drops might be made,
but the quantity falling in the same place would be the same at all heights;
unless, as you mention, the whole should be contracted in falling, the lines
described by all the drops converging, so that what set out to fall from a
cloud of many thousand acres, should reach the earth in perhaps a third of
that extent, of which I somewhat doubt. In the other cases we have two
experiments.
1. A dry glass bottle filled with very cold water, in a warm day, will
presently collect from the seemingly dry air that surrounds it a quantity of
water, that shall cover its surface and run down its sides, which perhaps is
done by the power wherewith the cold water attracts the fluid, common fire
that had been united with the dissolved water in the air, and drawing the fire
through the glass into itself, leaves the water on the outside.
2. An electrified body left in a room for some time, will be more covered
with dust than other bodies in the same room not electrified, which dust
seems to be attracted from the circumambient air.
Now we know that the rain, even in our hottest days, comes from a very
cold region. Its falling sometimes in the form of ice, shows this clearly; and
perhaps even the rain is snow or ice, when it first moves downwards,
though thawed in falling: and we know that the drops of rain are often
electrified: but those causes of addition to each drop of water, or piece of
hail, one would think could not long continue to produce the same effect;
since the air, through which the drops fall, must soon be stripped of its
previously dissolved water, so as to be no longer capable of augmenting
them. Indeed very heavy showers, of either, are never of long continuance;
but moderate rains often continue so long as to puzzle this hypothesis: so
that upon the whole I think, as I intimated before, that we are yet hardly ripe
for making one. ****
B. FRANKLIN.

FOOTNOTE:

[25] This letter is taken from the Memoirs of the Literary and Philosophical
Society of Manchester, Vol. II. page 126. It was communicated by the person to
whom it is addressed, and was read in the Society, January 21, 1784, as an
appendix to a paper by Dr. Percival on the same subject. Editor.

TO MR. NAIRNE, OF LONDON[26].

Proposing a slowly sensible Hygrometer for certain Purposes.

Passy, near Paris, Nov. 13, 1780.
Sir,
The qualities hitherto sought in a hygrometer, or instrument to discover
the degrees of moisture and dryness in the air, seem to have been, an
aptitude to receive humidity readily from a moist air, and to part with it is as
readily to a dry air. Different substances have been found to possess more or
less of this quality; but when we shall have found the substance that has it
in the greatest perfection, there will still remain some uncertainty in the
conclusions to be drawn from the degree shown by the instrument, arising
from the actual state of the instrument itself as to heat and cold. Thus, if two
bottles or vessels of glass or metal being filled, the one with cold and the
other with hot water, are brought into a room, the moisture of the air in the
room will attach itself in quantities to the surface of the cold vessel, while if
you actually wet the surface of the hot vessel, the moisture will immediately
quit it, and be absorbed by the same air. And thus, in a sudden change of the
air from cold to warm, the instrument remaining longer cold may condense
and absorb more moisture, and mark the air as having become more humid
than it is in reality, and the contrary in a change from warm to cold.
But if such a suddenly changing instrument could be freed from these
imperfections, yet when the design is to discover the different degrees of
humidity in the air of different countries, I apprehend the quick sensibility
of the instrument to be rather a disadvantage; since, to draw the desired
conclusions from it, a constant and frequent observation day and night in
each country will be necessary for a year or years, and the mean of each
different set of observations is to be found and determined. After all which
some uncertainty will remain respecting the different degrees of exactitude

with which different persons may have made and taken notes of their
observations.
For these reasons, I apprehend that a substance which, though capable of
being distended by moisture and contracted by dryness, is so slow in
receiving and parting with its humidity, that the frequent changes in the
atmosphere have not time to affect it sensibly, and which therefore should
gradually take nearly the medium of all those changes and preserve it
constantly, would be the most proper substance of which to make such an
hygrometer.
Such an instrument, you, my dear sir, though without intending it, have
made for me; and I, without desiring or expecting it, have received from
you. It is therefore with propriety that I address to you the following
account of it; and the more, as you have both a head to contrive and a hand
to execute the means of perfecting it. And I do this with greater pleasure, as
it affords me the opportunity of renewing that antient correspondence and
acquaintance with you, which to me was always so pleasing and so
instructive.
You may possibly remember, that in or about the year 1758, you made
for me a set of artificial magnets, six in number, each five and a half inches
long, half an inch broad, and one eighth of an inch thick. These, with two
pieces of soft iron, which together equalled one of the magnets, were
inclosed in a little box of mahogany wood, the grain of which ran with, and
not across, the length of the box: and the box was closed by a little shutter
of the same wood, the grain of which ran across the box; and the ends of
this shutting piece were bevelled so as to fit and slide in a kind of dovetail
groove when the box was to be shut or opened.
I had been of opinion, that good mahogany wood was not affected by
moisture so as to change its dimensions, and that it was always to be found
as the tools of the workman left it. Indeed the difference at different times
in the same country is so small as to be scarcely in a common way
observable. Hence the box, which was made so as to allow sufficient room
for the magnets to slide out and in freely, and, when in, afforded them so
much play that by shaking the box one could make them strike the opposite
sides alternately, continued in the same state all the time I remained in
England, which was four years, without any apparent alteration. I left

England in August 1762, and arrived at Philadelphia in October the same
year. In a few weeks after my arrival, being desirous of showing your
magnets to a philosophical friend, I found them so tight in the box, that it
was with difficulty I got them out; and constantly during the two years I
remained there, viz. till November 1764, this difficulty of getting them out
and in continued. The little shutter too, as wood does not shrink lengthways
of the grain, was found too long to enter its grooves, and, not being used,
was mislaid and lost; and I afterwards had another made that fitted.
In December 1764 I returned to England, and after some time I observed
that my box was become full big enough for my magnets, and too wide for
my new shutter; which was so much too short for its grooves, that it was apt
to fall out; and to make it keep in, I lengthened it by adding to each end a
little coat of sealing-wax.
I continued in England more than ten years, and during all that time, after
the first change, I perceived no alteration. The magnets had the same
freedom in their box, and the little shutter continued with the added sealing-
wax to fit its grooves, till some weeks after my second return to America.
As I could not imagine any other cause for this change of dimensions in
the box, when in the different countries, I concluded, first generally that the
air of England was moister than that of America. And this I supposed an
effect of its being an island, where every wind that blew must necessarily
pass over some sea before it arrived, and of course lick up some vapour. I
afterwards indeed doubted whether it might be just only so far as related to
the city of London, where I resided; because there are many causes of
moisture in the city air, which do not exist to the same degree in the
country; such as the brewers' and dyers' boiling caldrons, and the great
number of pots and tea-kettles continually on the fire, sending forth
abundance of vapour; and also the number of animals who by their breath
continually increase it; to which may be added, that even the vast quantity
of sea coals burnt there, do in kindling discharge a great deal of moisture.
When I was in England, the last time, you also made for me a little
achromatic pocket telescope, the body was brass, and it had a round case (I
think of thin wood) covered with shagrin. All the while I remained in
England, though possibly there might be some small changes in the
dimensions of this case, I neither perceived nor suspected any. There was

always comfortable room for the telescope to slip in and out. But soon after
I arrived in America, which was in May 1775, the case became too small
for the instrument, it was with much difficulty and various contrivances that
I got it out, and I could never after get it in again, during my stay there,
which was eighteen months. I brought it with me to Europe, but left the
case as useless, imagining that I should find the continental air of France as
dry as that of Pennsylvania, where my magnet box had also returned a
second time to its narrowness, and pinched the pieces, as heretofore,
obliging me too, to scrape the sealing-wax off the ends of the shutter.
I had not been long in France, before I was surprised to find, that my box
was become as large as it had always been in England, the magnets entered
and came out with the same freedom, and, when in, I could rattle them
against its sides; this has continued to be the case without sensible variation.
My habitation is out of Paris distant almost a league, so that the moist air of
the city cannot be supposed to have much effect upon the box. I am on a
high dry hill, in a free air, as likely to be dry as any air in France. Whence it
seems probable that the air of England in general may, as well as that of
London, be moister than the air of America, since that of France is so, and
in a part so distant from the sea.
The greater dryness of the air in America appears from some other
observations. The cabinet work formerly sent us from London, which
consisted in thin plates of fine wood glued upon fir, never would stand with
us; the vaneering, as those plates are called, would get loose and come off;
both woods shrinking, and their grains often crossing, they were forever
cracking and flying. And in my electrical experiments there, it was
remarkable, that a mahogany table, on which my jars stood under the prime
conductor to be charged, would often be so dry, particularly when the wind
had been some time at north-west, which with us is a very drying wind, as
to isolate the jars, and prevent their being charged till I had formed a
communication between their coatings and the earth. I had a like table in
London, which I used for the same purpose all the time I resided there; but
it was never so dry as to refuse conducting the electricity.
Now what I would beg leave to recommend to you, is, that you would
recollect, if you can, the species of mahogany of which you made my box,
for you know there is a good deal of difference in woods that go under that
name; or if that cannot be, that you would take a number of pieces of the

closest and finest grained mahogany that you can meet with, plane them to
the thinness of about a line, and the width of about two inches across the
grain, and fix each of the pieces in some instrument that you can contrive,
which will permit them to contract and dilate, and will show, in sensible
degrees, by a moveable hand upon a marked scale, the otherwise less
sensible quantities of such contraction and dilatation. If these instruments
are all kept in the same place while making, and are graduated together
while subject to the same degrees of moisture or dryness, I apprehend you
will have so many comparable hygrometers, which, being sent into different
countries, and continued there for some time, will find and show there the
mean of the different dryness and moisture of the air of those countries, and
that with much less trouble than by any hygrometer hitherto in use.
With great esteem, I am,
Dear Sir, your most obedient,
And most humble servant,
B. FRANKLIN.

FOOTNOTE:

[26] This letter is taken from the Transactions of the American Philosophical
Society, in which it was read, January 26, 1786. Editor.

T O D R . P. [ 2 7 ] I N L O N D O N .

Relating a curious Instance of the Effect of Oil on Water.

Philadelphia, Dec. 1, 1762.
Sir,
During our passage to Madeira, the weather being warm, and the cabin
windows constantly open for the benefit of the air, the candles at night
flared and run very much, which was an inconvenience. At Madeira, we got

oil to burn, and with a common glass tumbler or beaker, slung in wire, and
suspended to the cieling of the cabin, and a little wire hoop for the wick,
furnished with corks to float on the oil, I made an Italian lamp, that gave us
very good light all over the table.—The glass at bottom contained water to
about one third of its height; another third was taken up with oil; the rest
was left empty that the sides of the glass might protect the flame from the
wind. There is nothing remarkable in all this; but what follows is particular.
At supper, looking on the lamp, I remarked, that though the surface of the
oil was perfectly tranquil, and duly preserved its position and distance with
regard to the brim of the glass, the water under the oil was in great
commotion, rising and falling in irregular waves, which continued during
the whole evening. The lamp was kept burning as a watch light all night, till
the oil was spent, and the water only remained. In the morning I observed,
that though the motion of the ship continued the same, the water was now
quiet, and its surface as tranquil as that of the oil had been the evening
before.
At night again, when oil was put upon it, the water resumed its irregular
motions, rising in high waves almost to the surface of the oil, but without
disturbing the smooth level of that surface. And this was repeated every day
during the voyage.
Since my arrival in America, I have repeated the experiment frequently
thus. I have put a pack-thread round a tumbler, with strings of the same,
from each side, meeting above it in a knot at about a foot distance from the
top of the tumbler. Then putting in as much water as would fill about one
third part of the tumbler, I lifted it up by the knot, and swung it to and fro in
the air; when the water appeared to keep its place in the tumbler as steadily
as if it had been ice. But pouring gently in upon the water about as much
oil, and then again swinging it in the air as before, the tranquility before
possessed by the water, was transferred to the surface of the oil, and the
water under it was agitated with the same commotions as at sea.
I have shewn this experiment to a number of ingenious persons. Those
who are but slightly acquainted with the principles of hydrostatics, &c. are
apt to fancy immediately that they understand it, and readily attempt to
explain it; but their explanations have been different, and to me not very
intelligible. Others, more deeply skilled in those principles, seem to wonder
at it, and promise to consider it. And I think it is worth considering: for a

new appearance, if it cannot be explained by our old principles, may afford
us new ones, of use perhaps in explaining some other obscure parts of
natural knowledge.
I am, &c.
B. FRANKLIN.

FOOTNOTE:

[27] Dr. Pringle. Editor.

Of the Stilling of Waves by Means of Oil. Extracted from Sundry Letters between Benjamin Franklin,
L. L. D. F. R. S. William Brownrigg, M. D. F. R. S. and the Rev. Mr. Farish.

Read at the Royal Society, June 2, 1774.

Extract of a Letter from Dr. Brownrigg to Dr. Franklin, dated
Ormathwait, January 27, 1773.
By the enclosed from an old friend, a worthy clergyman at Carlisle,
whose great learning and extensive knowledge in most sciences would have
more distinguished him, had he been placed in a more conspicuous point of
view, you will find, that he had heard of your experiment on Derwent Lake,
and has thrown together what he could collect on that subject; to which I
have subjoined one experiment from the relation of another gentleman.

Extract of a Letter from the Rev. Mr. Farish, to Dr. Brownrigg.
I some time ago met with Mr. Dun, who surprised me with an account of
an experiment you had tried upon the Derwent Water, in company with Sir
John Pringle and Dr. Franklin. According to his representation, the water,

which had been in great agitation before, was instantly calmed upon
pouring in only a very small quantity of oil, and that to so great a distance
round the boat as seemed incredible. I have since had the same accounts
from others, but I suspect all of a little exaggeration. Pliny mentions this
property of oil as known particularly to the divers, who made use of it in his
days, in order to have a more steady light at the bottom.[28] The sailors, I
have been told, have observed something of the same kind in our days, that
the water is always remarkably smoother, in the wake of a ship that has
been newly tallowed, than it is in one that is foul. Mr. Pennant also
mentions an observation of the like nature made by the seal catchers in
Scotland. Brit. Zool. Vol. IV. Article Seal. When these animals are
devouring a very oily fish, which they always do under water, the waves
alone are observed to be remarkably smooth, and by this mark the
fishermen know where to look for them. Old Pliny does not usually meet
with all the credit I am inclined to think he deserves. I shall be glad to have
an authentic account of the Keswick experiment, and if it comes up to the
representations that have been made of it, I shall not much hesitate to
believe the old gentleman in another more wonderful phenomenon he
relates of stilling a tempest only by throwing up a little vinegar into the air.

Extract of a Letter to Dr. Brownrigg from Dr. Franklin.
London Nov. 7, 1773.
Dear Sir,
I thank you for the remarks of your learned friend at Carlisle. I had, when
a youth, read and smiled at Pliny's account of a practice among the seamen
of his time, to still the waves in a storm by pouring oil into the sea; which
he mentions, as well as the use made of oil by the divers; but the stilling a
tempest by throwing vinegar into the air had escaped me. I think with your
friend, that it has been of late too much the mode to slight the learning of
the ancients. The learned, too, are apt to slight too much the knowledge of
the vulgar. The cooling by evaporation was long an instance of the latter.
This art of smoothing the waves by oil is an instance of both.

Perhaps you may not dislike to have an account of all I have heard, and
learnt, and done in this way. Take it if you please as follows.
In 1757, being at sea in a fleet of 96 sail bound against Louisbourg, I
observed the wakes of two of the ships to be remarkably smooth, while all
the others were ruffled by the wind, which blew fresh. Being puzzled with
the differing appearance, I at last pointed it out to our captain, and asked
him the meaning of it. "The cooks," says he, "have, I suppose, been just
emptying their greasy water through the scuppers, which has greased the
sides of those ships a little;" and this answer he gave me with an air of some
little contempt, as to a person ignorant of what every body else knew. In my
own mind I at first slighted his solution, though I was not able to think of
another, but recollecting what I had formerly read in Pliny, I resolved to
make some experiment of the effect of oil on water, when I should have
opportunity.
Afterwards being again at sea in 1762, I first observed the wonderful
quietness of oil on agitated water, in the swinging glass lamp I made to
hang up in the cabin, as described in my printed papers[29]. This I was
continually looking at and considering, as an appearance to me
inexplicable. An old sea captain, then a passenger with me, thought little of
it, supposing it an effect of the same kind with that of oil put on water to
smooth it, which he said was a practice of the Bermudians when they would
strike fish, which they could not see, if the surface of the water was ruffled
by the wind. This practice I had never before heard of, and was obliged to
him for the information; though I thought him mistaken as to the sameness
of the experiment, the operations being different as well as the effects. In
one case, the water is smooth till the oil is put on, and then becomes
agitated. In the other it is agitated before the oil is applied, and then
becomes smooth. The same gentleman told me, he had heard it was a
practice with the fisherman of Lisbon when about to return into the river (if
they saw before them too great a surf upon the bar, which they apprehended
might fill their boats in passing) to empty a bottle or two of oil into the sea,
which would suppress the breakers, and allow them to pass safely. A
confirmation of this I have not since had an opportunity of obtaining: but
discoursing of it with another person, who had often been in the
Mediterranean, I was informed, that the divers there, who, when under
water in their business, need light, which the curling of the surface

interrupts by the refractions of so many little waves, let a small quantity of
oil now and then out of their mouths, which rising to the surface smooths it,
and permits the light to come down to them. All these informations I at
times revolved in my mind, and wondered to find no mention of them in our
books of experimental philosophy.
At length being at Clapham, where there is, on the common, a large
pond, which I observed one day to be very rough with the wind, I fetched
out a cruet of oil, and dropt a little of it on the water. I saw it spread itself
with surprising swiftness upon the surface; but the effect of smoothing the
waves was not produced; for I had applied it first on the leeward side of the
pond, where the waves were largest, and the wind drove my oil back upon
the shore. I then went to the windward side where they began to form; and
there the oil, though not more than a tea spoonful, produced an instant calm
over a space several yards square, which spread amazingly, and extended
itself gradually till it reached the lee side, making all that quarter of the
pond, perhaps half an acre, as smooth as a looking-glass.
After this I contrived to take with me, whenever I went into the country, a
little oil in the upper hollow joint of my bamboo cane, with which I might
repeat the experiment as opportunity should offer, and I found it constantly
to succeed.
In these experiments, one circumstance struck me with particular
surprise. This was the sudden, wide and forcible spreading of a drop of oil
on the face of the water, which I do not know that any body has hitherto
considered. If a drop of oil is put on a highly polished marble table, or on a
looking-glass that lies horizontally, the drop remains in its place, spreading
very little. But when put on water, it spreads instantly many feet round,
becoming so thin as to produce the prismatic colours, for a considerable
space, and beyond them so much thinner as to be invisible, except in its
effect of smoothing the waves at a much greater distance. It seems as if a
mutual repulsion between its particles took place as soon as it touched the
water, and a repulsion so strong as to act on other bodies swimming on the
surface, as straw, leaves, chips, &c. forcing them to recede every way from
the drop, as from a centre, leaving a large clear space. The quantity of this
force, and the distance to which it will operate, I have not yet ascertained;
but I think it a curious enquiry, and I wish to understand whence it arises.

In our journey to the north, when we had the pleasure of seeing you at
Ormathwaite, we visited the celebrated Mr. Smeaton, near Leeds. Being
about to show him the smoothing experiment on a little pond near his
house, an ingenious pupil of his, Mr. Jessop, then present, told us of an odd
appearance on that pond, which had lately occurred to him. He was about to
clean a little cup in which he kept oil, and he threw upon the water some
flies that had been drowned in the oil. These flies presently began to move,
and turned round on the water very rapidly, as if they were vigorously alive,
though on examination he found they were not so. I immediately concluded
that the motion was occasioned by the power of the repulsion above
mentioned, and that the oil issuing gradually from the spungy body of the
fly continued the motion. He found some more flies drowned in oil, with
which the experiment was repeated before us. To show that it was not any
effect of life recovered by the flies, I imitated it by little bits of oiled chips
and paper cut in the form of a comma, of the size of a common fly; when
the stream of repelling particles issuing from the point made the comma
turn round the contrary way. This is not a chamber experiment; for it cannot
be well repeated in a bowl or dish of water on a table. A considerable
surface of water is necessary to give room for the expansion of a small
quantity of oil. In a dish of water, if the smallest drop of oil be let fall in the
middle, the whole surface is presently covered with a thin greasy film
proceeding from the drop; but as soon as that film has reached the sides of
the dish, no more will issue from the drop, but it remains in the form of oil,
the sides of the dish putting a stop to its dissipation by prohibiting the
farther expansion of the film.
Our friend Sir John Pringle, being soon after in Scotland, learned there,
that those employed in the herring-fishery could at a distance see where the
shoals of herrings were, by the smoothness of the water over them, which
might possibly be occasioned, he thought, by some oiliness proceeding
from their bodies.
A gentleman from Rhode-island told me, it had been remarked, that the
harbour of Newport was ever smooth while any whaling vessels were in it;
which probably arose from hence, that the blubber which they sometimes
bring loose in the hold, or the leakage of their barrels, might afford some
oil, to mix with that water, which from time to time they pump out to keep

their vessel free, and that some oil might spread over the surface of the
water in the harbour, and prevent the forming of any waves.
This prevention I would thus endeavour to explain.
There seems to be no natural repulsion between water and air, such as to
keep them from coming into contact with each other. Hence we find a
quantity of air in water; and if we extract it by means of the air-pump, the
same water, again exposed to the air, will soon imbibe an equal quantity.
Therefore air in motion, which is wind, in passing over the smooth
surface of water, may rub, as it were, upon that surface, and raise it into
wrinkles, which, if the wind continues, are the elements of future waves.
The smallest wave once raised does not immediately subside, and leave
the neighbouring water quiet: but in subsiding raises nearly as much of the
water next to it, the friction of the parts making little difference. Thus a
stone dropped in a pool raises first a single wave round itself; and leaves it,
by sinking to the bottom; but that first wave subsiding raises a second, the
second a third, and so on in circles to a great extent.
A small power continually operating will produce a great action. A finger
applied to a weighty suspended bell can at first move it but little; if
repeatedly applied, though with no greater strength, the motion increases till
the bell swings to its utmost height, and with a force that cannot be resisted
by the whole strength of the arm and body. Thus the small first-raised
waves, being continually acted upon by the wind, are, though the wind does
not increase in strength, continually increased in magnitude, rising higher
and extending their bases, so as to include a vast mass of water in each
wave, which in its motion acts with great violence.
But if there be a mutual repulsion between the particles of oil, and no
attraction between oil and water, oil dropped on water will not be held
together by adhesion to the spot whereon it falls; it will not be imbibed by
the water; it will be at liberty to expand itself; and it will spread on a
surface that, besides being smooth to the most perfect degree of polish,
prevents, perhaps by repelling the oil, all immediate contact, keeping it at a
minute distance from itself; and the expansion will continue till the mutual
repulsion between the particles of the oil is weakened and reduced to
nothing by their distance.

Now I imagine that the wind, blowing over water thus covered with a
film of oil, cannot easily catch upon it, so as to raise the first wrinkles, but
slides over it, and leaves it smooth as it finds it. It moves a little the oil
indeed, which being between it and the water, serves it to slide with, and
prevents friction, as oil does between those parts of a machine, that would
otherwise rub hard together. Hence the oil dropped on the windward side of
a pond proceeds gradually to leeward, as may be seen by the smoothness it
carries with it, quite to the opposite side. For the wind being thus prevented
from raising the first wrinkles, that I call the elements of waves, cannot
produce waves, which are to be made by continually acting upon, and
enlarging those elements, and thus the whole pond is calmed.
Totally therefore we might suppress the waves in any required place, if
we could come at the windward place where they take their rise. This in the
ocean can seldom if ever be done. But perhaps something may be done on
particular occasions, to moderate the violence of the waves when we are in
the midst of them, and prevent their breaking where that would be
inconvenient.
For when the wind blows fresh, there are continually rising on the back
of every great wave a number of small ones, which roughen its surface, and
give the wind hold, as it were, to push it with greater force. This hold is
diminished, by preventing the generation of those small ones. And possibly
too, when a wave's surface is oiled, the wind, in passing over it, may rather
in some degree press it down, and contribute to prevent it, rising again,
instead of promoting it.
This as mere conjecture would have little weight, if the apparent effects
of pouring oil into the midst of waves were not considerable, and as yet not
otherwise accounted for.
When the wind blows so fresh, as that the waves are not sufficiently
quick in obeying its impulse, their tops being thinner and lighter are pushed
forward, broken, and turned over in a white foam. Common waves lift a
vessel without entering it; but these when large sometimes break above and
pour over it, doing great damage.
That this effect might in any degree be prevented, or the height and
violence of waves in the sea moderated, we had no certain account; Pliny's
authority for the practice of seamen in his time being slighted. But

discoursing lately on this subject with his excellency Count Bentinck, of
Holland, his son the honourable Captain Bentinck, and the learned
professor Allemand (to all whom I showed the experiment of smoothing in
a windy day the large piece of water at the head of the Green Park) a letter
was mentioned, which had been received by the Count from Batavia,
relative to the saving of a Dutch ship in a storm by pouring oil into the sea.
I much desired to see that letter, and a copy of it was promised me, which I
afterward received.

FOOTNOTES:

[28] Note by Dr. Brownrigg.
Sir Gilfred Lawson, who served long in the army at Gibraltar, assures me, that
the fishermen in that place are accustomed to pour a little oil on the sea, in order
to still its motion, that they may be enabled to see the oysters lying at its bottom;
which are there very large, and which they take up with a proper instrument.
This Sir Gilfred had often seen there performed, and said the same was practised
on other parts of the Spanish coast.
[29] See the preceding paper. Editor.

Extract of a Letter from Mr. Tengnagel to Count Bentinck, dated at Batavia, the 5th of
January, 1770.

"Near the islands Paul and Amsterdam, we met with a storm, which had
nothing particular in it worthy of being communicated to you, except that
the captain found himself obliged for greater safety in wearing the ship, to
pour oil into the sea, to prevent the waves breaking over her, which had an
excellent effect, and succeeded in preserving us. As he poured out but a
little at a time, the East India Company owes perhaps its ship to only six
demi-ames of oil-olive. I was present upon deck when this was done; and I
should not have mentioned this circumstance to you, but that we have found
people here so prejudiced against the experiment, as to make it necessary
for the officers on board and myself to give a certificate of the truth on this
head, of which we made no difficulty."

On this occasion, I mentioned to Captain Bentinck, a thought which had
occurred to me in reading the voyages of our late circumnavigators,
particularly where accounts are given of pleasant and fertile islands which
they much desired to land upon, when sickness made it more necessary, but
could not effect a landing through a violent surf breaking on the shore,
which rendered it impracticable. My idea was, that possibly by sailing to
and fro at some distance from such lee-shore, continually pouring oil into
the sea, the waves might be so much depressed, and lessened before they
reached the shore, as to abate the height and violence of the surf, and permit
a landing; which, in such circumstances, was a point of sufficient
importance to justify the expense of the oil that might be requisite for the
purpose. That gentleman, who is ever ready to promote what may be of
public utility, though his own ingenious inventions have not always met
with the countenance they merited, was so obliging as to invite me to
Portsmouth, where an opportunity would probably offer, in the course of a
few days, of making the experiment on some of the shores about Spithead,
in which he kindly proposed to accompany me, and to give assistance with
such boats as might be necessary. Accordingly, about the middle of October
last, I went with some friends to Portsmouth; and a day of wind happening,
which made a lee-shore between Haslar-hospital and the point near
Jillkecker, we went from the Centaur with the long-boat and barge towards
that shore. Our disposition was this: the long-boat was anchored about a
quarter of a mile from the shore; part of the company were landed behind
the point (a place more sheltered from the sea) who came round and placed
themselves opposite to the long-boat, where they might observe the surf,
and note if any change occurred in it upon using the oil. Another party, in
the barge, plied to windward of the long-boat, as far from her as she was
from the shore, making trips of about half a mile each, pouring oil
continually out of a large stone-bottle, through a hole in the cork, somewhat
bigger than a goose-quill. The experiment had not, in the main point, the
success we wished, for no material difference was observed in the height or
force of the surf upon the shore; but those who were in the long-boat could
observe a tract of smoothed water, the whole of the distance in which the
barge poured the oil, and gradually spreading in breadth towards the long-
boat. I call it smoothed, not that it was laid level; but because, though the
swell continued, its surface was not roughened by the wrinkles, or smaller
waves, before-mentioned; and none or very few white caps (or waves

whose tops turn over in foam) appeared in that whole space, though to
windward and leeward of it there were plenty; and a wherry, that came
round the point under sail, in her way to Portsmouth, seemed to turn into
that tract of choice, and to use it from end to end, as a piece of turnpike-
road.
It may be of use to relate the circumstances of an experiment that does
not succeed, since they may give hints of amendment in future trials: it is
therefore I have been thus particular. I shall only add what I apprehend may
have been the reason of our disappointment.
I conceive, that the operation of oil on water is, first, to prevent the
raising of new waves by the wind; and, secondly, to prevent its pushing
those before raised with such force, and consequently their continuance of
the same repeated height, as they would have done, if their surface were not
oiled. But oil will not prevent waves being raised by another power, by a
stone, for instance, falling into a still pool; for they then rise by the
mechanical impulse of the stone, which the greasiness on the surrounding
water cannot lessen or prevent, as it can prevent the winds catching the
surface and raising it into waves. Now waves once raised, whether by the
wind or any other power, have the same mechanical operation, by which
they continue to rise and fall, as a pendulum will continue to swing, a long
time after the force ceases to act by which the motion was first produced:
that motion will, however, cease in time; but time is necessary. Therefore,
though oil spread on an agitated sea may weaken the push of the wind on
those waves whose surfaces are covered by it, and so, by receiving less
fresh impulse, they may gradually subside; yet a considerable time, or a
distance through which they will take time to move, may be necessary to
make the effect sensible on any shore in a diminution of the surf: for we
know, that when wind ceases suddenly, the waves it has raised do not as
suddenly subside, but settle gradually, and are not quite down till after the
wind has ceased. So though we should, by oiling them, take off the effect of
wind on waves already raised, it is not to be expected that those waves
should be instantly levelled. The motion they have received will, for some
time, continue; and if the shore is not far distant, they arrive there so soon,
that their effect upon it will not be visibly diminished. Possibly, therefore, if
we had begun our operations at a greater distance, the effect might have

been more sensible. And perhaps we did not pour oil in sufficient quantity.
Future experiments may determine this.
I was, however, greatly obliged to Captain Bentinck, for the chearful and
ready aids he gave me: and I ought not to omit mentioning Mr. Banks, Dr.
Solander, General Carnoc, and Dr. Blagden, who all assisted at the
experiment, during that blustering unpleasant day, with a patience and
activity that could only be inspired by a zeal for the improvement of
knowledge, such especially as might possibly be of use to men in situations
of distress.
I would wish you to communicate this to your ingenious friend, Mr.
Farish, with my respects; and believe me to be, with sincere esteem,
Dear Sir,
Your most obedient, humble servant,
B. FRANKLIN.

T O S I R J O H N P R I N G L E , B A RT.

On the Difference of Navigation in shoal and deep Water.

Craven-street, May 10, 1768.
Sir,
You may remember, that when, we were travelling together in Holland,
you remarked, that the trackschuyt in one of the stages went slower than
usual, and enquired of the boatman, what might be the reason; who
answered, that it had been a dry season, and the water in the canal was low.
On being again asked if it was so low as that the boat touched the muddy
bottom; he said, no, not so low as that, but so low as to make it harder for
the horse to draw the boat. We neither of us at first could conceive that if
there was water enough for the boat to swim clear of the bottom, its being
deeper would make any difference; but as the man affirmed it seriously as a
thing well known among them; and as the punctuality required in their
stages was likely to make such difference, if any there were, more readily
observed by them, than by other watermen who did not pass so regularly
and constantly backwards and forwards in the same track; I began to
apprehend there might be something in it, and attempted to account for it
from this consideration, that the boat in proceeding along the canal, must in
every boat's length of her course, move out of her way a body of water,
equal in bulk to the room her bottom took up in the water; that the water so
moved must pass on each side of her and under her bottom to get behind
her; that if the passage under her bottom was straitened by the shallows,
more of that water must pass by her sides, and with a swifter motion, which
would retard her, as moving the contrary way; or that the water becoming
lower behind the boat than before, she was pressed back by the weight of its
difference in height, and her motion retarded by having that weight
constantly to overcome. But as it is often lost time to attempt accounting for
uncertain facts, I determined to make an experiment of this when I should
have convenient time and opportunity.
After our return to England, as often as I happened to be on the Thames, I
enquired of our watermen whether they were sensible of any difference in
rowing over shallow or deep water. I found them all agreeing in the fact,

that there was a very great difference, but they differed widely in expressing
the quantity of the difference; some supposing it was equal to a mile in six,
others to a mile in three, &c. As I did not recollect to have met with any
mention of this matter in our philosophical books, and conceiving that if the
difference should really be great, it might be an object of consideration in
the many projects now on foot for digging new navigable canals in this
island, I lately put my design of making the experiment in execution, in the
following manner.
I provided a trough of plained boards fourteen feet long, six inches wide
and six inches deep, in the clear, filled with water within half an inch of the
edge, to represent a canal. I had a loose board of nearly the same length and
breadth, that, being put into the water, might be sunk to any depth, and
fixed by little wedges where I would chuse to have it stay, in order to make
different depths of water, leaving the surface at the same height with regard
to the sides of the trough. I had a little boat in form of a lighter or boat of
burthen, six inches long, two inches and a quarter wide, and one inch and a
quarter deep. When swimming, it drew one inch water. To give motion to
the boat, I fixed one end of a long silk thread to its bow, just even with the
water's edge, the other end passed over a well-made brass pully, of about an
inch diameter, turning freely on a small axis; and a shilling was the weight.
Then placing the boat at one end of the trough, the weight would draw it
through the water to the other.
Not having a watch that shows seconds, in order to measure the time
taken up by the boat in passing from end to end, I counted as fast as I could
count to ten repeatedly, keeping an account of the number of tens on my
fingers. And as much as possible to correct any little inequalities in my
counting, I repeated the experiment a number of times at each depth of
water, that I might take the medium. And the following are the results.
Water 1½ inches deep. 2 inches. 4½ inches.
1st exp. 100 94 79
2 104 93 78
3 104 91 77
4 106 87 79
5 100 88 79
6 99 86 80

7 100 90 79
8 100 88 81
—— —— ——
813 717 632
—— —— ——
Medium 101 Medium 89 Medium 79

I made many other experiments, but the above are those in which I was
most exact; and they serve sufficiently to show that the difference is
considerable. Between the deepest and shallowest it appears to be
somewhat more than one fifth. So that supposing large canals and boats and
depths of water to bear the same proportions, and that four men or horses
would draw a boat in deep water four leagues in four hours, it would require
five to draw the same boat in the same time as far in shallow water; or four
would require five hours.
Whether this difference is of consequence enough to justify a greater
expence in deepening canals, is a matter of calculation, which our ingenious
engineers in that way will readily determine.
I am, &c.
B. FRANKLIN.

T O M R . A L P H O N S U S L E R O Y, M E M B E R O F S E V E R A L
A C A D E M I E S AT P A R I S . [ 3 0 ]

Containing sundry Maritime Observations.

At Sea, on board the London Packet, Capt. Truxton.

Aug. 1785.
Sir,
Your learned writings on the navigation of the antients, which contain a
great deal of curious information, and your very ingenious contrivances for
improving the modern sails (voilure) of which I saw with great pleasure a

successful trial on the river Seine, have induced me to submit to your
consideration and judgment, some thoughts I have had on the latter subject.
Those mathematicians, who have endeavoured to improve the swiftness
of vessels, by calculating to find the form of least resistance, seem to have
considered a ship as a body moving through one fluid only, the water; and
to have given little attention to the circumstance of her moving through
another fluid, the air. It is true that when a vessel sails right before the wind,
this circumstance is of no importance, because the wind goes with her; but
in every deviation from that course, the resistance of the air is something,
and becomes greater in proportion as that deviation increases. I wave at
present the consideration of those different degrees of resistance given by
the air to that part of the hull which is above water, and confine myself to
that given to the sails; for their motion through the air is resisted by the air,
as the motion of the hull through the water is resisted by the water, though
with less force as the air is a lighter fluid. And to simplify the discussion as
much as possible, I would state one situation only, to wit, that of the wind
upon the beam, the ship's course being directly across the wind; and I would
suppose the sail set in an angle of 45 degrees with the keel, as in the
following figure; wherein (Plate VI, Fig. 1.)

Plate VI. Vol. II. page 163.

Maritime Observations.

View larger image here
Published as the Act directs, April 1, 1806, by Longman, Hurst, Rees & Orme, Paternoster Row.

A B represents the body of the vessel, C D the position of the sail, EEE
the direction of the wind, MM the line of motion. In observing this figure it
will appear, that so much of the body of the vessel as is immersed in the
water must, to go forward, remove out of its way what water it meets with
between the pricked lines FF. And the sail, to go forward, must move out of
its way all the air its whole dimension meets with between the pricked lines
CG and DG. Thus both the fluids give resistance to the motion, each in
proportion to the quantity of matter contained in the dimension to be
removed. And though the air is vastly lighter than the water, and therefore
more easily removed, yet the dimension being much greater its effect is
very considerable.
It is true that in the case stated, the resistance given by the air between
those lines to the motion of the sail is not apparent to the eye, because the
greater force of the wind, which strikes it in the direction EEE, overpowers

its effect, and keeps the sail full in the curve a, a, a, a, a. But suppose the
wind to cease, and the vessel in a calm to be impelled with the same
swiftness by oars, the sail would then appear filled in the contrary curve b,
b, b, b, b, when prudent men would immediately perceive, that the air
resisted its motion, and would order it to be taken in.
Is there any possible means of diminishing this resistance, while the same
quantity of sail is exposed to the action of the wind, and therefore the same
force obtained from it? I think there is, and that it may be done by dividing
the sail into a number of parts, and placing those parts in a line one behind
the other; thus instead of one sail extending from C to D, figure 2, if four
sails containing together the same quantity of canvas, were placed as in
figure 3, each having one quarter of the dimensions of the great sail, and
exposing a quarter of its surface to the wind, would give a quarter of the
force; so that the whole force obtained from the wind would be the same,
while the resistance from the air would be nearly reduced to the space
between the pricked lines a b and c d, before the foremost sail.
It may perhaps be doubted whether the resistance from the air would be
so diminished; since possibly each of the following small sails having also
air before it, which must be removed, the resistance on the whole would be
the same.
This is then a matter to be determined by experiment. I will mention one
that I many years since made with success for another purpose; and I will
propose another small one easily made. If that too succeeds, I should think
it worth while to make a larger, though at some expense, on a river boat;
and perhaps time, and the improvements experience will afford, may make
it applicable with advantage to larger vessels.
Having near my kitchen chimney a round hole of eight inches diameter,
through which was a constant steady current of air, increasing or
diminishing only as the fire increased or diminished, I contrived to place
my jack so as to receive that current; and taking off the flyers, I fixed in
their stead on the same pivot a round tin plate of nearly the same diameter
with the hole; and having cut it in radial lines almost to the centre, so as to
have six equal vanes, I gave to each of them the obliquity of forty-five
degrees. They moved round, without the weight, by the impression only of
the current of air, but too slowly for the purpose of roasting. I suspected that

the air struck by the back of each vane might possibly by its resistance
retard the motion; and to try this, I cut each of them into two, and I placed
the twelve, each having the same obliquity, in a line behind each other,
when I perceived a great augmentation in its velocity, which encouraged me
to divide them once more, and, continuing the same obliquity, I placed the
twenty-four behind each other in a line, when the force of the wind being
the same, and the surface of vane the same, they moved round with much
greater rapidity, and perfectly answered my purpose.
The second experiment that I propose, is, to take two playing cards of the
same dimensions, and cut one of them transversely into eight equal pieces;
then with a needle string them upon two threads one near each end, and
place them so upon the threads that, when hung up, they may be one exactly
over the other, at a distance equal to their breadth, each in a horizontal
position; and let a small weight, such as a bird-shot, be hung under them, to
make them fall in a straight line when let loose. Suspend also the whole
card by threads from its four corners, and hang to it an equal weight, so as
to draw it downwards when let fall, its whole breadth pressing against the
air. Let those two bodies be attached, one of them to one end of a thread a
yard long, the other to the other end. Extend a twine under the ceiling of a
room, and put through it at thirty inches distance two pins bent in the form
of fish-hooks. On these two hooks hang the two bodies, the thread that
connects them extending parallel to the twine, which thread being cut, they
must begin to fall at the same instant. If they take equal time in falling to
the floor, it is a proof that the resistance of the air is in both cases equal. If
the whole card requires a longer time, it shows that the sum of the
resistances to the pieces of the cut card is not equal to the resistance of the
whole one[31].
This principle so far confirmed, I would proceed to make a larger
experiment, with a shallop, which I would rig in this manner. (Plate VI. Fig.
4.)
A B is a long boom, from which are hoisted seven jibs, a, b, c, d, e, f, g,
each a seventh part of the whole dimensions, and as much more as will fill
the whole space when set in an angle of forty-five degrees, so that they may
lap when going before the wind, and hold more wind when going large.
Thus rigged, when going right before the wind, the boom should be brought

at right angles with the keel, by means of the sheet ropes C D, and all the
sails hauled flat to the boom.
These positions of boom and sails to be varied as the wind quarters. But
when the wind is on the beam, or when you would turn to windward, the
boom is to be hauled right fore and aft, and the sails trimmed according as
the wind is more or less against your course.
It seems to me, that the management of a shallop so rigged would be very
easy, the sails being run up and down separately, so that more or less sail
may be made at pleasure; and I imagine, that there being full as much sail
exposed to the force of the wind which impels the vessel in its course, as if
the whole were in one piece, and the resistance of the dead air against the
foreside of the sail being diminished, the advantage of swiftness would be
very considerable; besides that the vessel would lie nearer the wind.
Since we are on the subject of improvements in navigation, permit me to
detain you a little longer with a small relative observation. Being, in one of
my voyages, with ten merchant-ships under convoy of a frigate at anchor in
Torbay, waiting for a wind to go to the westward; it came fair, but brought
in with it a considerable swell. A signal was given for weighing, and we put
to sea all together; but three of the ships left their anchors, their cables
parting just as the anchors came a-peak. Our cable held, and we got up our
anchor; but the shocks the ship felt before the anchor got loose from the
ground, made me reflect on what might possibly have caused the breaking
of the other cables; and I imagined it might be the short bending of the
cable just without the hause-hole, from a horizontal to an almost vertical
position, and the sudden violent jerk it receives by the rising of the head of
the ship on the swell of a wave while in that position. For example, suppose
a vessel hove up so as to have her head nearly over her anchor, which still
keeps its hold, perhaps in a tough bottom; if it were calm, the cable still out
would form nearly a perpendicular line, measuring the distance between the
hause-hole and the anchor; but if there is a swell, her head in the trough of
the sea will fall below the level, and when lifted on the wave will be much
above it. In the first case the cable will hang loose and bend perhaps as in
figure 5. In the second case, figure 6, the cable will be drawn straight with a
jerk, must sustain the whole force of the rising ship, and must either loosen
the anchor, resist the rising force of the ship, or break. But why does it
break at the hause-hole?

Let us suppose it a cable of three inches diameter, and represented by
figure 7. If this cable is to be bent round the corner A, it is evident that
either the part of the triangle contained between the letters a, b, c, must
stretch considerably, and those most that are nearest the surface; or that the
parts between d, e, f, must be compressed; or both, which most probably
happens. In this case the lower half of the thickness affords no strength
against the jerk, it not being strained, the upper half bears the whole, and
the yarns near the upper surface being first and most strained, break first,
and the next yarns follow; for in this bent situation they cannot bear the
strain all together, and each contributes its strength to the whole, as they do
when the cable is strained in a straight line.
To remedy this, methinks it would be well to have a kind of large pulley
wheel, fixed in the hause-hole, suppose of two feet diameter, over which the
cable might pass; and being there bent gradually to the round of the wheel,
would thereby be more equally strained, and better able to bear the jerk,
which may save the anchor, and by that means in the course of the voyage
may happen to save the ship.
One maritime observation more shall finish this letter. I have been a
reader of news-papers now near seventy years, and I think few years pass
without an account of some vessel met with at sea, with no living soul on
board, and so many feet of water in her hold, which vessel has nevertheless
been saved and brought into port: and when not met with at sea, such
forsaken vessels have often come ashore on some coast. The crews, who
have taken to their boats and thus abandoned such vessels, are sometimes
met with and taken up at sea by other ships, sometimes reach a coast, and
are sometimes never heard of. Those that give an account of quitting their
vessels generally say, that she sprung a leak, that they pumped for some
time, that the water continued to rise upon them, and that, despairing to
save her, they had quitted her lest they should go down with her. It seems
by the event that this fear was not always well founded, and I have
endeavoured to guess at the reason of the people's too hasty
discouragement.
When a vessel springs a leak near her bottom, the water enters with all
the force given by the weight of the column of water, without, which force
is in proportion to the difference of level between the water without and that
within. It enters therefore with more force at first and in greater quantity,

than it can afterwards when the water within is higher. The bottom of the
vessel too is narrower, so that the same quantity of water coming into that
narrow part, rises faster than when the space for it to flow in is larger. This
helps to terrify. But as the quantity entering is less and less as the surfaces
without and within become more nearly equal in height, the pumps that
could not keep the water from rising at first, might afterwards be able to
prevent its rising higher, and the people might have remained on board in
safety, without hazarding themselves in an open boat on the wide ocean.
(Fig. 8.)
Besides the greater equality in the height of the two surfaces, there may
sometimes be other causes that retard the farther sinking of a leaky vessel.
The rising water within may arrive at quantities of light wooden work,
empty chests, and particularly empty water-casks, which if fixed so as not
to float themselves may help to sustain her. Many bodies which compose a
ship's cargo may be specifically lighter than water, all these when out of
water are an additional weight to that of the ship, and she is in proportion
pressed deeper into the water; but as soon as these bodies are immersed,
they weigh no longer on the ship, but on the contrary, if fixed, they help to
support her, in proportion as they are specifically lighter than the water. And
it should be remembered, that the largest body of a ship may be so balanced
in the water, that an ounce less or more of weight may leave her at the
surface or sink her to the bottom. There are also certain heavy cargoes, that,
when the water gets at them, are continually dissolving, and thereby
lightening the vessel, such as salt and sugar. And as to water-casks
mentioned above, since the quantity of them must be great in ships of war
where the number of men consume a great deal of water every day, if it had
been made a constant rule to bung them up as fast as they were emptied,
and to dispose the empty casks in proper situations, I am persuaded that
many ships which have been sunk in engagements, or have gone down
afterwards, might with the unhappy people have been saved; as well as
many of those which in the last war foundered, and were never heard of.
While on this topic of sinking, one cannot help recollecting the well known
practice of the Chinese, to divide the hold of a great ship into a number of
separate chambers by partitions tight caulked (of which you gave a model
in your boat upon the Seine) so that if a leak should spring in one of them
the others are not affected by it; and though that chamber should fill to a
level with the sea, it would not be sufficient to sink the vessel. We have not

imitated this practice. Some little disadvantage it might occasion in the
stowage is perhaps one reason, though that I think might be more than
compensated by an abatement in the insurance that would be reasonable,
and by a higher price taken of passengers, who would rather prefer going in
such a vessel. But our seafaring people are brave, despise danger, and reject
such precautions of safety, being cowards only in one sense, that of fearing
to be thought afraid.
I promised to finish my letter with the last observation, but the garrulity
of the old man has got hold of me, and as I may never have another
occasion of writing on this subject, I think I may as well now, once for all,
empty my nautical budget, and give you all the thoughts that have in my
various long voyages occurred to me relating to navigation. I am sure that
in you they will meet with a candid judge, who will excuse my mistakes on
account of my good intention.
There are six accidents that may occasion the loss of ships at sea. We
have considered one of them, that of foundering by a leak. The other five
are, 1. Oversetting by sudden flaws of wind, or by carrying sail beyond the
bearing. 2. Fire by accident or carelessness. 3. A heavy stroke of lightning,
making a breach in the ship, or firing the powder. 4. Meeting and shocking
with other ships in the night. 5. Meeting in the night with islands of ice.
To that of oversetting, privateers in their first cruize have, as far as has
fallen within my knowledge or information, been more subject than any
other kind of vessels. The double desire of being able to overtake a weaker
flying enemy, or to escape when pursued by a stronger, has induced the
owners to overmast their cruizers, and to spread too much canvass; and the
great number of men, many of them not seamen, who being upon deck
when a ship heels suddenly are huddled down to leeward, and increase by
their weight the effect of the wind. This therefore should be more attended
to and guarded against, especially as the advantage of lofty masts is
problematical. For the upper sails have greater power to lay a vessel more
on her side, which is not the most advantageous position for going swiftly
through the water. And hence it is that vessels, which have lost their lofty
masts, and been able to make little more sail afterwards than permitted the
ship to sail upon an even keel, have made so much way, even under jury
masts, as to surprize the mariners themselves. But there is besides,
something in the modern form of our ships that seems as if calculated

expressly to allow their oversetting more easily. The sides of a ship, instead
of spreading out as they formerly did in the upper works, are of late years
turned in, so as to make the body nearly round, and more resembling a cask.
I do not know what the advantages of this construction are, except that such
ships are not easily boarded. To me it seems a contrivance to have less room
in a ship at nearly the same expense. For it is evident that the same timber
and plank consumed in raising the sides from a to b, and from d to c, would
have raised them from a to e, and from d to f, fig. 9. In this form all the
spaces between e, a, b, and c, d, f, would have been gained, the deck would
have been larger, the men would have had more room to act, and not have
stood so thick in the way of the enemy's shot; and the vessel, the more she
was laid down on her side, the more bearing she would meet with, and more
effectual to support her, as being farther from the centre. Whereas in the
present form, her ballast makes the chief part of her bearing, without which
she would turn in the sea almost as easily as a barrel. More ballast by this
means becomes necessary, and that sinking a vessel deeper in the water
occasions more resistance to her going through it. The Bermudian sloops
still keep with advantage to the old spreading form. The islanders in the
great Pacific ocean, though they have no large ships, are the most expert
boat-sailors in the world, navigating that sea safely with their proas, which
they prevent oversetting by various means. Their sailing proas for this
purpose have outriggers generally to windward, above the water, on which,
one or more men are placed, to move occasionally further from or nearer to
the vessel as the wind freshens or slackens. But some have their outriggers
to leeward, which, resting on the water, support the boat so as to keep her
upright when pressed down by the wind. Their boats moved by oars or
rather by paddles are, for long voyages, fixed two together by cross bars of
wood that keep them at some distance from each other, and so render their
oversetting next to impossible. How far this may be practicable in larger
vessels, we have not yet sufficient experience. I know of but one trial made
in Europe, which was about one hundred years since, by Sir William Petty.
He built a double vessel, to serve as a packet boat between England and
Ireland. Her model still exists in the museum of the Royal Society, where I
have seen it. By the accounts we have of her, she answered well the purpose
of her construction, making several voyages; and though wrecked at last by
a storm, the misfortune did not appear owing to her particular construction,
since many other vessels of the common form were wrecked at the same

time. The advantage of such a vessel is, that she needs no ballast, therefore
swims either lighter or will carry more goods; and that passengers are not so
much incommoded by her rolling: to which may be added, that if she is to
defend herself by her cannon, they will probably have more effect, being
kept more generally in a horizontal position, than those in common vessels.
I think, however, that it would be an improvement of that model, to make
the sides which are opposed to each other perfectly parallel, though the
other sides are formed as in common thus, figure 10.
The building of a double ship would indeed be more expensive in
proportion to her burthen; and that perhaps is sufficient to discourage the
method.
The accident of fire is generally well guarded against by the prudent
captain's strict orders against smoking between decks, or carrying a candle
there out of a lanthorn. But there is one dangerous practice which frequent
terrible accidents have not yet been sufficient to abolish; that of carrying
store-spirits to sea in casks. Two large ships, the Seraphis and the Duke of
Athol, one an East-Indiaman, the other a frigate, have been burnt within
these two last years, and many lives miserably destroyed, by drawing spirits
out of a cask near a candle. It is high time to make it a general rule, that all
the ship's store of spirits should be carried in bottles.
The misfortune by a stroke of lightning I have in my former writings
endeavoured to show a method of guarding against, by a chain and pointed
rod, extending, when run up, from above the top of the mast to the sea.
These instruments are now made and sold at a reasonable price by Nairne &
Co. in London, and there are several instances of success attending the use
of them. They are kept in a box, and may be ran up and fixed in about five
minutes, on the apparent approach of a thunder gust.
Of the meeting and shocking with other ships in the night, I have known
two instances in voyages between London and America. In one both ships
arrived though much damaged, each reporting their belief that the other
must have gone to the bottom. In the other, only one got to port; the other
was never afterwards heard of. These instances happened many years ago,
when the commerce between Europe and America was not a tenth part of
what it is at present, ships of course thinner scattered, and the chance of
meeting proportionably less. It has long been the practice to keep a look-out

before in the channel, but at sea it has been neglected. If it is not at present
thought worth while to take that precaution, it will in time become of more
consequence; since the number of ships at sea is continually augmenting. A
drum frequently beat, or a bell rung in a dark night, might help to prevent
such accidents.
Islands of ice are frequently seen off the banks of Newfoundland, by
ships going between North-America and Europe. In the day time they are
easily avoided, unless in a very thick fog. I remember two instances of
ship's running against them in the night. The first lost her bowsprit, but
received little other damage. The other struck where the warmth of the sea
had wasted the ice next to it, and a part hung over above. This perhaps
saved her, for she was under great way; but the upper part of the cliff taking
her foretopmast, broke the shock, though it carried away the mast. She
disengaged herself with some difficulty, and got safe into port; but the
accident shows the possibility of other ships being wrecked and sunk by
striking those vast masses of ice, of which I have seen one that we judged to
be seventy feet high above the water, consequently eight times as much
under water; and it is another reason for keeping a good look-out before,
though far from any coast that may threaten danger.
It is remarkable, that the people we consider as savages have improved
the art of sailing and rowing-boats in several points beyond what we can
pretend to. We have no sailing-boats equal to the flying proas of of the
South Seas, no rowing or paddling-boat equal to that of the Greenlanders
for swiftness and safety. The birch canoes of the North-American Indians
have also some advantageous properties. They are so light that two men
may carry one of them over land, which is capable of carrying a dozen upon
the water; and in heeling they are not so subject to take in water as our
boats, the sides of which are lowest in the middle where it is most likely to
enter, this being highest in that part, as in figure 11.
The Chinese are an enlightened people, the most antiently civilized of
any existing, and their arts are antient, a presumption in their favour: their
method of rowing their boats differs from ours, the oars being worked either
two a-stern as we scull, or on the sides with the same kind of motion, being
hung parallel to the keel on a rail and always acting in the water, not
perpendicular to the side as ours are, nor lifted out at every stroke, which is

a loss of time, and the boat in the interval loses motion. They see our
manner, and we theirs, but neither are disposed to learn of or copy the other.
To the several means of moving boats mentioned above, may be added
the singular one lately exhibited at Javelle, on the Seine below Paris, where
a clumsy boat was moved across that river in three minutes by rowing, not
in the water, but in the air, that is, by whirling round a set of windmill vanes
fixed to a horizontal axis, parallel to the keel, and placed at the head of the
boat. The axis was bent into an elbow at the end, by the help of which it
was turned by one man at a time. I saw the operation at a distance. The four
vanes appeared to be about five feet long, and perhaps two and a half wide.
The weather was calm. The labour appeared to be great for one man, as the
two several times relieved each other. But the action upon the air by the
oblique surfaces of the vanes must have been considerable, as the motion of
the boat appeared tolerably quick going and returning; and she returned to
the same place from whence she first set out, notwithstanding the current.
This machine is since applied to the moving of air-balloons: an instrument
similar may be contrived to move a boat by turning under water.
Several mechanical projectors have at different times proposed to give
motion to boats, and even to ships, by means of circular rowing, or paddles
placed on the circumference of wheels to be turned constantly on each side
of the vessel; but this method, though frequently tried, has never been found
so effectual as to encourage a continuance of the practice. I do not know
that the reason has hitherto been given. Perhaps it may be this, that great
part of the force employed contributes little to the motion. For instance,
(fig. 12) of the four paddles a, b, c, d, all under water, and turning to move a
boat from X to Y, c has the most power, b nearly though not quite as much,
their motion being nearly horizontal; but the force employed in moving a, is
consumed in pressing almost downright upon the water till it comes to the
place of b; and the force employed in moving d is consumed in lifting the
water till d arrives at the surface; by which means much of the labour is
lost. It is true, that by placing the wheels higher out of the water, this waste
labour will be diminished in a calm, but where a sea runs, the wheels must
unavoidably be often dipt deep in the waves, and the turning of them
thereby rendered very laborious to little purpose.
Among the various means of giving motion to a boat, that of M.
Bernoulli appears one of the most singular, which was to have fixed in the

boat a tube in the form of an L, the upright part to have a funnel-kind of
opening at top, convenient for filling the tube with water; which,
descending and passing through the lower horizontal part, and issuing in the
middle of the stern, but under the surface of the river, should push the boat
forward. There is no doubt that the force of the descending water would
have a considerable effect, greater in proportion to the height from which it
descended; but then it is to be considered, that every bucket-full pumped or
dipped up into the boat, from its side or through its bottom, must have its
vis inertiæ overcome so as to receive the motion of the boat, before it can
come to give motion by its descent; and that will be a deduction from the
moving power. To remedy this, I would propose the addition of another
such L pipe, and that they should stand back to back in the boat thus, figure
13, the forward one being worked as a pump, and sucking in the water at
the head of the boat, would draw it forward while pushed in the same
direction by the force at the stern. And after all it should be calculated
whether the labour of pumping would be less than that of rowing. A fire-
engine might possibly in some cases be applied in this operation with
advantage.
Perhaps this labour of raising water might be spared, and the whole force
of a man applied to the moving of a boat by the use of air instead of water;
suppose the boat constructed in this form, figure 14. A, a tube round or
square of two feet diameter, in which a piston may move up and down. The
piston to have valves in it, opening inwards to admit air when the piston
rises; and shutting, when it is forced down by means of the lever B turning
on the centre C. The tube to have a valve D, to open when the piston is
forced down, and let the air pass out at E, which striking forcibly against
the water abaft must push the boat forward. If there is added an air-vessel F
properly valved and placed, the force would continue to act while a fresh
stroke is taken with the lever. The boat-man might stand with his back to
the stern, and putting his hands behind him, work the motion by taking hold
of the cross bar at B, while another should steer; or if he had two such
pumps, one on each side of the stern, with a lever for each hand, he might
steer himself by working occasionally more or harder with either hand, as
watermen now do with a pair of sculls. There is no position in which the
body of a man can exert more strength than in pulling right upwards. To
obtain more swiftness, greasing the bottom of a vessel is sometimes used,
and with good effect. I do not know that any writer has hitherto attempted

to explain this. At first sight one would imagine, that though the friction of
a hard body, sliding on another hard body, and the resistance occasioned by
that friction, might be diminished by putting grease between them, yet that
a body sliding on a fluid, such as water, should have no need of, nor receive
any advantage from such greasing. But the fact is not disputed. And the
reason perhaps may be this—The particles of water have a mutual
attraction, called the attraction of adhesion. Water also adheres to wood, and
to many other substances, but not to grease: on the contrary they have a
mutual repulsion, so that it is a question whether when oil is poured on
water, they ever actually touch each other; for a drop of oil upon water,
instead of sticking to the spot where it falls, as it would if it fell on a
looking-glass, spreads instantly to an immense distance in a film extremely
thin, which it could not easily do if it touched and rubbed or adhered even
in a small degree to the surface of the water. Now the adhesive force of
water to itself, and to other substances, may be estimated from the weight of
it necessary to separate a drop, which adheres, while growing, till it has
weight enough to force the separation and break the drop off. Let us
suppose the drop to be the size of a pea, then there will be as many of these
adhesions as there are drops of that size touching the bottom of a vessel,
and these must be broken by the moving power, every step of her motion
that amounts to a drop's breadth: and there being no such adhesions to break
between the water and a greased bottom, may occasion the difference.
So much respecting the motion of vessels. But we have sometimes
occasion to stop their motion; and if a bottom is near enough we can cast
anchor: where there are no soundings, we have as yet no means to prevent
driving in a storm, but by lying-to, which still permits driving at the rate of
about two miles an hour; so that in a storm continuing fifty hours, which is
not an uncommon case, the ship may drive one hundred miles out of her
course; and should she in that distance meet with a lee shore, she may be
lost.
To prevent this driving to leeward in deep water, a swimming anchor is
wanting, which ought to have these properties.
1. It should have a surface so large as, being at the end of a hauser in the
water, and placed perpendicularly, should hold so much of it, as to bring the
ship's head to the wind, in which situation the wind has least power to drive
her.

2. It should be able by its resistance to prevent the ship's receiving way.
3. It should be capable of being situated below the heave of the sea, but
not below the undertow.
4. It should not take up much room in the ship.
5. It should be easily thrown out, and put into its proper situation.
6. It should be easy to take in again, and stow away.
An ingenious old mariner, whom I formerly knew, proposed, as a
swimming anchor for a large ship, to have a stem of wood twenty-five feet
long and four inches square, with four boards of 18, 16, 14, and 12, feet
long, and one foot wide, the boards to have their substance thickened
several inches in the middle by additional wood, and to have each a four
inch square hole through its middle, to permit its being slipt on occasionally
upon the stem, and at right angles with it; where all being placed and fixed
at four feet distance from each other, it would have the appearance of the
old mathematical instrument called a forestaff. This thrown into the sea, and
held by a hauser veered out to some length, he conceived would bring a
vessel up, and prevent her driving, and when taken in might be stowed
away by separating the boards from the stem. Figure 15. Probably such a
swimming anchor would have some good effect, but it is subject to this
objection, that lying on the surface of the sea, it is liable to be hove forward
by every wave, and thereby give so much leave for the ship to drive.
Two machines for this purpose have occurred to me, which, though not
so simple as the above, I imagine would be more effectual, and more easily
manageable. I will endeavour to describe them, that they may be submitted
to your judgment, whether either would be serviceable; and if they would,
to which we should give the preference.
The first is to be formed, and to be used in the water on almost the same
principles with those of a paper kite used in the air. Only as the paper kite
rises in the air, this is to descend in the water. Its dimensions will be
different for ships of different size.
To make one of suppose fifteen feet high; take a small spar of that length
for the back-bone, AB, figure 16, a smaller of half that length CD, for the
cross piece. Let these be united by a bolt at E, yet so as that by turning on
the bolt they may be laid parallel to each other. Then make a sail of strong

canvas, in the shape of figure 17. To form this, without waste of sail-cloth,
sew together pieces of the proper length, and for half the breadth, as in
figure 18, then cut the whole in the diagonal lines a, b, c, and turn the piece
F so as to place its broad part opposite to that of the piece G, and the piece
H in like manner opposite to I, which when all sewed together will appear
as in fig. 17. This sail is to be extended on the cross of figure 16, the top
and bottom points well secured to the ends of the long spar; the two side
points d, e, fastened to the ends of two cords, which coming from the angle
of the loop (which must be similar to the loop of a kite) pass through two
rings at the ends of the short spar, so as that on pulling upon the loop the
sail will be drawn to its extent. The whole may, when aboard, be furled up,
as in figure 19, having a rope from its broad end, to which is tied a bag of
ballast for keeping that end downwards when in the water, and at the other
end another rope with an empty keg at its end to float on the surface; this
rope long enough to permit the kite's descending into the undertow, or if
you please lower into still water. It should be held by a hauser. To get it
home easily, a small loose rope may be veered out with it, fixed to the keg.
Hauling on that rope will bring the kite home with small force, the
resistance being small as it will then come end ways.
It seems probable that such a kite at the end of a long hauser would keep
a ship with her head to the wind, and, resisting every tug, would prevent her
driving so fast as when her side is exposed to it, and nothing to hold her
back. If only half the driving is prevented, so as that she moves but fifty
miles instead of the hundred during a storm, it may be some advantage,
both in holding so much distance as is saved, and in keeping from a lee-
shore. If single canvas should not be found strong enough to bear the tug
without splitting, it may be doubled, or strengthened by a netting behind it,
represented by figure 20.
The other machine for the same purpose, is to be made more in the form
of an umbrella, as represented, figure 21. The stem of the umbrella a square
spar of proper length, with four moveable arms, of which two are
represented C, C, figure 22. These arms to be fixed in four joint cleats, as D,
D, &c. one on each side of the spar, but so as that the four arms may open
by turning on a pin in the joint. When open they form a cross, on which a
four-square canvas sail is to be extended, its corners fastened to the ends of
the four arms. Those ends are also to be stayed by ropes fastened to the

stem or spar, so as to keep them short of being at right angles with it: and to
the end of one of the arms should be hung the small bag of ballast, and to
the end of the opposite arm the empty keg. This, on being thrown into the
sea, would immediately open; and when it had performed its function, and
the storm over, a small rope from its other end being pulled on, would turn
it, close it, and draw it easily home to the ship. This machine seems more
simple in its operation, and more easily manageable than the first, and
perhaps may be as effectual[32].
Vessels are sometimes retarded, and sometimes forwarded in their
voyages, by currents at sea, which are often not perceived. About the year
1769 or 70, there was an application made by the board of customs at
Boston, to the lords of the treasury in London, complaining that the packets
between Falmouth and New-York, were generally a fortnight longer in their
passages, than merchant-ships from London to Rhode-Island, and proposing
that for the future they should be ordered to Rhode-Island instead of New-
York. Being then concerned in the management of the American post-
office, I happened to be consulted on the occasion; and it appearing strange
to me that there should be such a difference between two places, scarce a
day's run asunder, especially when the merchant-ships are generally deeper
laden, and more weakly manned than the packets, and had from London the
whole length of the river and channel to run before they left the land of
England, while the packets had only to go from Falmouth, I could not but
think the fact misunderstood or misrepresented. There happened then to be
in London a Nantucket sea-captain of my acquaintance, to whom I
communicated the affair. He told me he believed the fact might be true; but
the difference was owing to this, that the Rhode-Island captains were
acquainted with the gulf-stream, which those of the English packets were
not. We are well acquainted with that stream, says he, because in our pursuit
of whales, which keep near the sides of it, but are not to be met with in it,
we run down along the sides, and frequently cross it to change our side: and
in crossing it have sometimes met and spoke with those packets, who were
in the middle of it, and stemming it. We have informed them that they were
stemming a current, that was against them to the value of three miles an
hour; and advised them to cross it and get out of it; but they were too wise
to be counselled by simple American fishermen. When the winds are but
light, he added, they are carried back by the current more than they are
forwarded by the wind: and if the wind be good, the subtraction of 70 miles

a day from their course is of some importance. I then observed it was a pity
no notice was taken of this current upon the charts, and requested him to
mark it out for me, which he readily complied with, adding directions for
avoiding it in sailing from Europe to North-America. I procured it to be
engraved by order from the general post-office, on the old chart of the
Atlantic, at Mount and Page's, Tower-hill; and copies were sent down to
Falmouth for the captains of the packets, who slighted it however; but it is
since printed in France, of which edition I hereto annex a copy.
This stream is probably generated by the great accumulation of water on
the eastern coast of America between the tropics, by the trade-winds which
constantly blow there. It is known that a large piece of water ten miles
broad and generally only three feet deep, has by a strong wind had its
waters driven to one side and sustained so as to become six feet deep, while
the windward side was laid dry. This may give some idea of the quantity
heaped up on the American coast, and the reason of its running down in a
strong current through the islands into the bay of Mexico, and from thence
issuing through the gulph of Florida, and proceeding along the coast to the
banks of Newfoundland, where it turns off towards and runs down through
the Western Islands. Having since crossed this stream several times in
passing between America and Europe, I have been attentive to sundry
circumstances relating to it, by which to know when one is in it; and besides
the gulph weed with which it is interspersed, I find that it is always warmer
than the sea on each side of it, and that it does not sparkle in the night: I
annex hereto the observations made with the thermometer in two voyages,
and possibly may add a third. It will appear from them, that the
thermometer may be an useful instrument to a navigator, since currents
coming from the northward into southern seas, will probably be found
colder than the water of those seas, as the currents from southern seas into
northern are found warmer. And it is not to be wondered that so vast a body
of deep warm water, several leagues wide, coming from between the tropics
and issuing out of the gulph into the northern seas, should retain its warmth
longer than the twenty or thirty days required to its passing the banks of
Newfoundland. The quantity is too great, and it is too deep to be suddenly
cooled by passing under a cooler air. The air immediately over it, however,
may receive so much warmth from it as to be rarefied and rise, being
rendered lighter than the air on each side of the stream; hence those airs
must flow in to supply the place of the rising warm air, and, meeting with

each other, form those tornados and water-spouts frequently met with, and
seen near and over the stream; and as the vapour from a cup of tea in a
warm room, and the breath of an animal in the same room, are hardly
visible, but become sensible immediately when out in the cold air, so the
vapour from the gulph stream, in warm latitudes is scarcely visible, but
when it comes into the cool air from Newfoundland, it is condensed into the
fogs, for which those parts are so remarkable.
The power of wind to raise water above its common level in the sea is
known to us in America, by the high tides occasioned in all our sea-ports
when a strong north-easter blows against the gulph stream.
The conclusion from these remarks is, that a vessel from Europe to
North-America may shorten her passage by avoiding to stem the stream, in
which the thermometer will be very useful; and a vessel from America to
Europe may do the same by the same means of keeping in it. It may have
often happened accidentally, that voyages have been shortened by these
circumstances. It is well to have the command of them.
But may there not be another cause, independent of winds and currents,
why passages are generally shorter from America to Europe than from
Europe to America? This question I formerly considered in the following
short paper.

On board the Pennsylvania Packet, Capt. Osborne.

At Sea, April 5, 1775.
"Suppose a ship to make a voyage eastward from a place in lat. 40° north,
to a place in lat. 50° north, distance in longitude 75 degrees.
"In sailing from 40 to 50, she goes from a place where a degree of
longitude is about eight miles greater than in the place she is going to. A
degree is equal to four minutes of time; consequently the ship in the harbour
she leaves, partaking of the diurnal motion of the earth, moves two miles in
a minute faster, than when in the port she is going to; which is 120 miles in
an hour.
"This motion in a ship and cargo is of great force; and if she could be
lifted up suddenly from the harbour in which she lay quiet, and set down

instantly in the latitude of the port she was bound to, though in a calm, that
force contained in her would make her run a great way at a prodigious rate.
This force must be lost gradually in her voyage, by gradual impulse against
the water, and probably thence shorten the voyage. Query, In returning does
the contrary happen, and is her voyage thereby retarded and lengthened?"
[33]

Would it not be a more secure method of planking ships, if, instead of
thick single planks laid horizontally, we were to use planks of half the
thickness, and lay them double and across each other as in figure 23? To me
it seems that the difference of expence would not be considerable, and that
the ship would be both tighter and stronger.
The securing of the ship is not the only necessary thing; securing the
health of the sailors, a brave and valuable order of men, is likewise of great
importance. With this view the methods so successfully practised by
Captain Cook in his long voyages cannot be too closely studied or carefully
imitated. A full account of those methods is found in Sir John Pringle's
speech, when the medal of the Royal Society was given to that illustrious
navigator. I am glad to see in his last voyage that he found the means
effectual which I had proposed for preserving flour, bread, &c. from
moisture and damage. They were found dry and good after being at sea four
years. The method is described in my printed works, page 452, fifth
edition[34]. In the same, page 469, 470[35], is proposed a means of allaying
thirst in case of want of fresh water. This has since been practised in two
instances with success. Happy if their hunger, when the other provisions are
consumed, could be relieved as commodiously; and perhaps in time this
may be found not impossible. An addition might be made to their present
vegetable provision, by drying various roots in slices by the means of an
oven. The sweet potatoe of America and Spain is excellent for this purpose.
Other potatoes, with carrots, parsnips and turnips, might be prepared and
preserved in the same manner.
With regard to make-shifts in cases of necessity, seamen are generally
very ingenious themselves. They will excuse however the mention of two or
three. If they happen in any circumstance, such as after shipwreck, taking to
their boat, or the like, to want a compass, a fine sewing-needle laid on clear
water in a cup will generally point to the north, most of them being a little
magnetical, or may be made so by being strongly rubbed or hammered,

lying in a north and south direction. If their needle is too heavy to float by
itself, it may be supported by little pieces of cork or wood. A man who can
swim, may be aided in a long traverse by his handkerchief formed into a
kite, by two cross sticks extending to the four corners; which, being raised
in the air when the wind is fair and fresh, will tow him along while lying on
his back. Where force is wanted to move a heavy body, and there are but
few hands and no machines, a long and strong rope may make a powerful
instrument. Suppose a boat is to be drawn up on a beach, that she may be
out of the surf; a stake drove into the beach where you would have the boat
drawn, and another to fasten the end of the rope to, which comes from the
boat, and then applying what force you have to pull upon the middle of the
rope at right angles with it, the power will be augmented in proportion to
the length of rope between the posts. The rope being fastened to the stake A,
and drawn upon in the direction C D, will slide over the stake B; and when
the rope is bent to the angle A D B, represented by the pricked line in figure
24, the boat will be at B.
Some sailors may think the writer has given himself unnecessary trouble
in pretending to advise them; for they have a little repugnance to the advice
of landmen, whom they esteem ignorant and incapable of giving any worth
notice; though it is certain that most of their instruments were the invention
of landmen. At least the first vessel ever made to go on the water was
certainly such. I will therefore add only a few words more, and they shall be
addressed to passengers.
When you intend a long voyage, you may do well to keep your intention
as much as possible a secret, or at least the time of your departure;
otherwise you will be continually interrupted in your preparations by the
visits of friends and acquaintance, who will not only rob you of the time
you want, but put things out of your mind, so that when you come to sea,
you have the mortification to recollect points of business that ought to have
been done, accounts you intended to settle, and conveniencies you had
proposed to bring with you, &c. &c. all which have been omitted through
the effect of these officious friendly visits. Would it not be well if this
custom could be changed; if the voyager after having, without interruption,
made all his preparations, should use some of the time he has left, in going
himself to take leave of his friends at their own houses, and let them come
to congratulate him on his happy return.

It is not always in your power to make a choice in your captain, though
much of your comfort in the passage may depend on his personal character,
as you must for so long a time be confined to his company, and under his
direction; if he be a sensible, sociable, good-natured, obliging man, you will
be so much the happier. Such there are; but if he happens to be otherwise,
and is only skilful, careful, watchful and active in the conduct of his ship,
excuse the rest, for these are the essentials.
Whatever right you may have by agreement in the mass of stores laid in
by him for the passengers, it is good to have some particular things in your
own possession, so as to be always at your own command.
1. Good water, that of the ship being often bad. You can be sure of having
it good only by bottling it from a clear spring or well and in clean bottles. 2.
Good tea. 3. Coffee ground. 4. Chocolate. 5. Wine of the sort you
particularly like, and cyder. 6. Raisins. 7. Almonds. 8. Sugar. 9. Capillaire.
10. Lemons. 11. Jamaica spirits. 12. Eggs greased. 13. Diet bread 14.
Portable soup. 15. Rusks. As to fowls, it is not worth while to have any
called yours, unless you could have the feeding and managing of them
according to your own judgment under your own eye. As they are generally
treated at present in ships, they are for the most part sick, and their flesh
tough and hard as whit-leather. All seamen have an opinion, broached I
supposed at first prudently, for saving of water when short, that fowls do
not know when they have drank enough, and will kill themselves if you
give them too much, so they are served with a little only once in two days.
This is poured into troughs that lie sloping, and therefore immediately runs
down to the lower end. There the fowls ride upon one another's backs to get
at it, and some are not happy enough to reach and once dip their bills in it.
Thus tantalized, and tormented with thirst, they cannot digest their dry food,
they fret, pine, sicken and die. Some are found dead, and thrown overboard
every morning, and those killed for the table are not eatable. Their troughs
should be in little divisions, like cups, to hold the water separately, figure
25. But this is never done. The sheep and hogs are therefore your best
dependance for fresh meat at sea, the mutton being generally tolerable and
the pork excellent.
It is possible your captain may have provided so well in the general
stores, as to render some of the particulars above recommended of little or
no use to you. But there are frequently in the ship poorer passengers, who

are taken at a lower price, lodge in the steerage, and have no claim to any of
the cabin provisions, or to any but those kinds that are allowed the sailors.
These people are sometimes dejected, sometimes sick, there may be women
and children among them. In a situation where there is no going to market,
to purchase such necessaries, a few of these your superfluities distributed
occasionally may be of great service, restore health, save life, make the
miserable happy, and thereby afford you infinite pleasure.
The worst thing in ordinary merchant ships is the cookery. They have no
professed cook, and the worst hand as a seaman is appointed to that office,
in which he is not only very ignorant but very dirty. The sailors have
therefore a saying, that God sends meat and the devil cooks. Passengers
more piously disposed, and willing to believe heaven orders all things for
the best, may suppose, that, knowing the sea-air and constant exercise by
the motion of the vessel would give us extraordinary appetites, bad cooks
were kindly sent to prevent our eating too much; or that, foreseeing we
should have bad cooks, good appetites were furnished to prevent our
starving. If you cannot trust to these circumstances, a spirit-lamp, with a
blaze-pan, may enable you to cook some little things for yourself; such as a
hash, a soup, &c. And it might be well also to have among your stores some
potted meats, which if well put up will keep long good. A small tin oven, to
place with the open side before the fire, may be another good utensil, in
which your own servant may roast for you a bit of pork or mutton. You will
sometimes be induced to eat of the ship's salt beef, as it is often good. You
will find cyder the best quencher of that thirst which salt meat or fish
occasions. The ship biscuit is too hard for some sets of teeth. It may be
softened by toasting. But rusk is better; for being made of good fermented
bread, sliced and baked a second time, the pieces imbibe the water easily,
soften immediately, digest more kindly, and are therefore more wholesome
than the unfermented biscuit. By the way, rusk is the true original biscuit, so
prepared to keep for sea, biscuit in French signifying twice baked. If your
dry peas boil hard, a two-pound iron shot put with them into the pot, will by
the motion of the ship grind them as fine as mustard.
The accidents I have seen at sea with large dishes of soup upon a table,
from the motion of the ship, have made me wish, that our potters or
pewterers would make soup-dishes in divisions, like a set of small bowls
united together, each containing about sufficient for one person, in some

such form as fig. 26; for then when the ship should make a sudden heel, the
soup would not in a body flow over one side, and fall into people's laps and
scald them, as is sometimes the case, but would be retained in the separate
divisions, as in figure 27.
After these trifles, permit the addition of a few general reflections.
Navigation, when employed in supplying necessary provisions to a country
in want, and thereby preventing famines, which were more frequent and
destructive before the invention of that art, is undoubtedly a blessing to
mankind. When employed merely in transporting superfluities, it is a
question whether the advantage of the employment it affords is equal to the
mischief of hazarding so many lives on the ocean. But when employed in
pillaging merchants and transporting slaves, it is clearly the means of
augmenting the mass of human misery. It is amazing to think of the ships
and lives risqued in fetching tea from China, coffee from Arabia, sugar and
tobacco from America, all which our ancestors did well without. Sugar
employs near one thousand ships, tobacco almost as many. For the utility of
tobacco there is little to be said; and for that of sugar, how much more
commendable would it be if we could give up the few minutes gratification
afforded once or twice a day by the taste of sugar in our tea, rather than
encourage the cruelties exercised in producing it. An eminent French
moralist says, that when he considers the wars we excite in Africa to obtain
slaves, the numbers necessarily slain in those wars, the many prisoners who
perish at sea by sickness, bad provisions, foul air, &c. &c. in the
transportation, and how many afterwards die from the hardships of slavery,
he cannot look on a piece of sugar without conceiving it stained with spots
of human blood! Had he added the consideration of the wars we make to
take and retake the sugar islands from one another, and the fleets and armies
that perish in those expeditions, he might have seen his sugar not merely
spotted, but thoroughly dyed scarlet in grain. It is these wars that make the
maritime powers of Europe, the inhabitants of London and Paris, pay dearer
for sugar than those of Vienna, a thousand miles from the sea; because their
sugar costs not only the price they pay for it by the pound, but all they pay
in taxes to maintain the fleets and armies that fight for it.
With great esteem, I am, Sir,
Your most obedient humble servant,

B. FRANKLIN.

FOOTNOTES:

[30] This letter and the annexed paper on the Gulph stream, are taken from the
Transactions of the American Philosophical Society, in which they were read
December 2, 1785. Editor.
[31] The motion of the vessel made it inconvenient to try this simple experiment
at sea, when the proposal of it was written. But it has been tried since we came
on shore, and succeeded as the other.
[32] Captain Truxton, on board whose ship this was written, has executed this
proposed machine; he has given six arms to the umbrella, they are joined to the
stem by iron hinges, and the canvas is double. He has taken it with him to China.
February, 1786.
[33] Since this paper was read at the Society, an ingenious member, Mr.
Patterson, has convinced the writer that the returning voyage would not, from
this cause, be retarded.
[34] See the Paper referred to, Vol. I. p. 376. Editor.
[35] See Vol. II. p. 104. Editor.

Plate VII. Vol. II. page 197.

A CHART of The GULPH STREAM.

View larger image here
Published as the Act directs, April 1, 1806, by Longman, Hurst, Rees & Orme, Paternoster Row.

Remarks upon the Navigation from Newfoundland to New-York, in order to avoid the Gulph
Stream on one hand, and on the other the Shoals that lie to the Southward of Nantucket
and of St. George's Banks.

After you have passed the banks of Newfoundland in about the 44th
degree of latitude, you will meet with nothing, till you draw near the Isle of
Sables, which we commonly pass in latitude 43. Southward of this isle, the
current is found to extend itself as far north as 41° 20′ or 30′, then it turns
towards the E. S. E. or S. E. ¼ E.

Having passed the Isle of Sables, shape your course for the St. George's
Banks, so as to pass them in about latitude 40°, because the current
southward of those banks reaches as far north as 39°. The shoals of those
banks lie in 41° 35′.
After having passed St. George's Banks, you must, to clear Nantucket,
form your course so as to pass between the latitudes 38° 30′ and 40° 45′.
The most southern part of the shoals of Nantucket lie in about 40° 45′.
The northern part of the current directly to the south of Nantucket is felt in
about latitude 38° 30′.
By observing these directions and keeping between the stream and the
shoals, the passage from the Banks of Newfoundland to New-York,
Delaware, or Virginia, may be considerably shortened; for so you will have
the advantage of the eddy current, which moves contrary to the Gulph
Stream. Whereas if to avoid the shoals you keep too far to the southward,
and get into that stream, you will be retarded by it at the rate of 60 or 70
miles a day.
The Nantucket whale-men being extremely well acquainted with the
Gulph Stream, its course, strength, and extent, by their constant practice of
whaling on the edges of it, from their island quite down to the Bahamas,
this draft of that stream was obtained from one of them, Captain Folges, and
caused to be engraved on the old chart in London, for the benefit of
navigators, by
B. FRANKLIN.

Note, The Nantucket captains who are acquainted with this stream, make
their voyages from England to Boston in as short a time generally as others
take in going from Boston to England, viz. from twenty to thirty days.
A stranger may know when he is in the Gulph Stream, by the warmth of
the water, which is much greater than that of the water on each side of it. If
then he is bound to the westward, he should cross the stream to get out of it
as soon as possible.
B. FRANKLIN.

Observations of the Warmth of the Sea-water, &c. by Fahrenheit's Thermometer, in crossing
the Gulph Stream; with other Remarks made on board the Pennsylvania Packet, Capt.
Osborne, bound from London to Philadelphia, in April and May, 1775.

Temp. of Temp. of Latitude Longitude
Date Hour Wind Course Distance Remarks
Air. Wat. N. W.
April
62
10
11 61
12 64
13 65
14 65 ° ′ ° ′
Much gulph weed; saw
26 60 70 37 39 60 38
a whale.
Colour of water
27 60 70 SSE WbS 37 13 62 29
changed.
28 8 A.M. 70 64 SW WNW 37 48 64 35 No gulph weed.
— 6 P.M. 67 60 34 Sounded, no bottom.
Much light in the water
29 8 A.M. 63 71 N W 44 37 26 66 0
last night.
— 5 P.M. 65 72 NE 57 Water again of the
usual deep sea
— 11 dit. 66 66 NWbN WbS 57
colour, little or no
30 8 A.M. 64 70 NE WbN 69 light in it at night.
Frequent gulph weed,
— 12 62 70 EbS 24 37 20 68 53
water continues of
sea colour, little
— 6 P.M. 64 72 ESE WbN 43
light.
— 10 dit. 65 65 S 25 Much light.
Much light all last
May 1 7 A.M. 68 63 60
night.
Colour of water
— 12 65 56 SSW WNW 44 38 13 72 23
changed.
— 4 P.M. 64 56 WbN 21
— 10 dit. 64 57 SW WNW 31 Much light.
Much light. Thunder-
2 8 A.M. 62 53 18 38 43 74 3
gust.
— 12 60 53 WSW NW 18
— 6 P.M. 64 55 NW WSW 15
— 10 65 55 NbW WbN 10
3 7 A.M. 62 54 30 38 30 75 0

Observations of the Warmth of the Sea-water, &c. by Fahrenheit's Thermometer; with other
Remarks made on board the Reprisal, Capt. Wycks, bound from Philadelphia to France, in
October and November, 1776.

Hour Hour Temp. Temp. of
Date Wind Course Distance Lat. N. Long. W. Remarks
A.M. P.M. of Air Water
Octo. Left the capes
10 76 70 SSE EbS 135 38 12 70 30
31 Thursday night,
— 4 71 October 29, 1776
Nov.
10 78 WSW E½N 109 No ob. 68 12
1
— 4 71 81
2 8 71 75 N
— 12 78 141 ditto. 65 23
— 4 67 76 Some sparks in the
water these two last
3 8 76 NW ESE½E nights.
— 12 76 EbS 160 37 0 62 7
— 4 70 76
4 9 68 76 NbE Ditto.
— 1 76 194 36 26 58 8
— 4 68 76
— 8 78
5 8 68 76 NE Ditto.
— 12 70 75 163 35 21 55 3
— 4 75
— 8 75
6 8 76 EbN S50E
— 12 77 75 35 33 53 52
7 8 78 SEbE N30W
— 12 77 108 36 6 52 46
— 4 77
8 9 75 77 SbE N49E
— 12 77 175 38 2 50 1
— 4 77
9 9 75 77
— 12 75 70 SW N33E 175 39 39 46 55

OBSERVATIONS MADE ON BOARD THE REPRISAL, CONTINUED.

Hour Hour Temp. Temp. of
Date Wind Course Distance Latit. N. Long. W. Remarks.
A.M. P.M. of Air Water
Nov 9 4 71
10 8 70 68
— 12 64 E N 17 E 64 40 39 46 27
11 8 63
— 12 61 SE N8E 41 41 19 46 19
12 8 56 59
— 4 69 NNW N 80 E 120 41 39 43 42
13 all day 68 E S 82 E 69 41 29 42 10
14 8 70 70 N 74 E 111 42 0 39 57
— Noon 72 ESE
— 4 71
15 8 61 69
— Noon 68 WSW N 70 E 186 43 3 35 51
— 4 67
16 Noon 65 67 SW N 67 W 48 43 22 34 50
— 4 63
17 8 63 ESE N 19 E 56 44 15 34 25
18 all day 65 SbW N 75 E 210 45 6 29 43 Some gulph weed.
19 Noon 65 64 SW N 80 E 238 45 46 24 2
20 8 62 N S 80 E 155 45 19 20 30
— 4 60
21 9 62 S N 88 E 94 45 22 18 17
22 10 60 62 SSW S 89 E 133 45 19 15 19
23 Noon 61 WSW S 86 E 194 45 6 10 35
24 do. 60 NNE N 78 E 191 45 46 6 10
25 do. 60 NE S 76 E 125 45 4 3 23
26 do. 56 60 E N 73 E 31 45 13 2 20
27 do. 58 Soundings off Bellisle.
28 do. 54 56

A Journal of a Voyage from the Channel between France and England towards America.

Therm. A.M. Therm. P.M. Variation of the
Dates Latit. N. Long. W. Winds Course Distance
Air Water Air Water Needle
July 29 62 57 { These are taken on an
30 62 58 63 58 average of 24 hours. }
31 60 58 62 62 Miles. West.
Aug 1 49 15 4 15 63 62 60 64 East SW ½W 60 22° 0
2 48 28 8 58 64 64 64 63 ESE WbS ½S 174
3 47 0 12 13 60 67 omitted NE SW bW 160
4 45 0 15 43 66 66 do. 66 NWbW SW ½W 190
5 43 5 17 25 67 65 65 68 NE SW bS 131 20 0
6 41 3 19 44 70 68 71 69 NE SW ½S 166 16 30
7 38 45 21 34 70 70 68 70 NE SSW ¾W 165 11 30
8 36 42 23 10 72 71 73 72 NE SSW ¾W 149 11 15
9 35 40 25 40 73 73 73 74 NE WSW ¼S 137
10 35 0 27 0 71 73 77 75 NW WSW ¾S 76
Therm.
11 33 51 28 42 74 74 76 77 North SW ¾W 112
Noon
12 33 30 31 30 76 75 76 76 North W ¾S 143 A. W.
13 33 17 33 32 76 76 78 77 NE W½S 103 77 78
14 33 22 34 31 76 76 81 79 SSE W½N 50 81 79
15 33 45 35 0 78 79 79 78 WNW SW ¼W 35 79 79
16 34 14 35 30 79 78 81 80 West NW ½N 38 81 80
17 35 37 36 4 80 79 80 78 WSW NNW 75 80 78
18 36 7 37 16 80 78 omitted NW bW WNW ½N 65 80 79
19 36 38 38 0 78 77 78 77 WSW NW ½W 49 79 77

Journal of a Voyage, &c. continued.

Therm.
Therm. A.M. Therm. P.M. Variation of the
Dates Latit. N. Long. W. Winds Course Distance Noon
Needle
Air Water Air Water A. W.
Aug 20 37 38 38 6 78 76 omitted West N¼W 62 77 75
21 36 15 38 26 73 74 78 76 WNW SbW 82 77 75
22 35 40 38 44 77 76 80 77 WbS SSW 38 80 77
23 35 35 40 52 79 77 78 75 North W¼S 100 omitted.
24 35 12 41 31 75 73 75 74 WNW SWbW 41 75 74
WNW¾
25 35 40 42 33 79 76 79 76 WbN 60 80 76
N
26 35 30 42 44 79 76 80 76 SWbW SW½S 14 80 76
27 35 14 43 23 79 77 81 79 West WSW¼S 38 81 78
28 34 23 44 0 78 76 78 78 NNE SWbS 60 78 78
29 34 12 45 52 77 78 78 78 NE W¼S 94 8 0 79 78
30 34 5 48 31 78 78 78 78 East W½S 134 78 78
31 34 20 51 4 80 79 81 79 East W¾S 129 80 80
Sept 1 34 20 52 47 81 78 omitted SSW W¼N 86 83 80
WbN½
2 34 55 55 12 81 80 83 80 SW 125 83 80
W
3 35 30 57 24 83 80 83 80 SWbS WbN½N 114 6 0 84 81
4 35 50 59 1 82 80 83 80 SW½W WbN¼N 82 83 81
5 35 55 61 0 81 80 82 81 SSW W¼N 96 82 81
6 36 20 62 30 80 81 79 80 NWbN WbN 75 78 80
7 34 50 63 10 87 80 78 81 NWbN SSW 86 78 81
8 34 45 64 40 75 79 75 79 North W¼S 74 75 79
9 35 43 66 42 75 79 77 73 NE WNW 108 78 80
10 37 20 68 40 77 73 77 70 ENE NW 126 78 72

N.B. Longitude is reckoned from London, and the Thermometer is according to Fahrenheit.

OBSERVATIONS.
July 31. At one P.M. the Start bore WNW. distant six leagues.
August 1. The water appears luminous in the ship's wake.
---- 2. The temperature of the water is taken at eight in the morning and at eight in the evening.
---- 6. The water appears less luminous.
---- 7. Formegas SW. dist 32½ deg. St. Mary's SW½S. 33 leagues.
---- 8. From this date the temperature of the water is taken at eight in the morning and at six in the evening.
---- 10. Moonlight, which prevents the luminous appearance of the water.
---- 11. A strong southerly current.
---- 12. Ditto. From this date the temperature of the air and water was taken at noon, as well as morning and evening.
---- 16. Northerly current.
---- 19. First saw gulph weed.
---- 21. Southerly current.
---- 22. Again saw gulph weed.

---- 24. The water appeared luminous in a small degree before the moon rose.
---- 29. No moon, yet very little light in the water.
---- 30. Much gulph weed to-day.
---- 31. Ditto.
Sept. 1. Ditto.
---- 2. A little more light in the water.
---- 4. No gulph weed to-day. More light in the water.
---- 5. Some gulph weed again.
---- 6. Little light in the water. A very hard thunder-gust in the night.
---- 7. Little gulph weed.
---- 8. More light in the water. Little gulph weed.
---- 9. Little gulph weed. Little light in the water last evening.
---- 10. Saw some beds of rock-weed; and we were surprised to observe the water six degrees colder by the thermometer than
the preceding noon.
This day (10th) the thermometer still kept descending, and at five in the morning of the 11th, it was in water as low as 70, when
we struck soundings. The same evening the pilot came on board, and we found our ship about five degrees of longitude a-head of
the reckoning, which our captain accounted for by supposing our course to have been near the edge of the gulph stream, and thus
an eddy-current always in our favour. By the distance we ran from Sept. 9, in the evening, till we struck soundings, we must have
then been at the western edge of the gulph stream, and the change in the temperature of the water was probably owing to our
suddenly passing from that current, into the waters of our own climate.
On the 14th of August the following experiment was made. The weather being perfectly calm, an empty bottle, corked very
tight, was sent down 20 fathoms, and it was drawn up still empty. It was then sent down again 35 fathoms, when the weight of the
water having forced in the cork, it was drawn up full; the water it contained was immediately tried by the thermometer, and found
to be 70, which was six degrees colder than at the surface: the lead and bottle were visible, but not very distinctly so, at the depth
of 12 fathoms, but when only 7 fathoms deep, they were perfectly seen from the ship. This experiment was thus repeated Sept. 11,
when we were in soundings of 18 fathoms. A keg was previously prepared with a valve at each end, one opening inward, the other
outward; this was sent to the bottom in expectation that by the valves being both open when going down, and both shut when
coming up, it would keep within it the water received at bottom. The upper valve performed its office well, but the under one did
not shut quite close, so that much of the water was lost in hauling it up the ship's side. As the water in the keg's passage upwards
could not enter at the top, it was concluded that what water remained in it was of that near the ground, and on trying this by the
thermometer, it was found to be at 58, which was 12 degrees colder than at the surface.

This last Journal was obligingly kept for me by Mr. J. Williams, my fellow-passenger in the London Packet, who made all the
experiments with great exactness.

TO MR. O. N[36].

On the Art of Swimming.

[No date.]
Dear Sir,
I cannot be of opinion with you that it is too late in life for you to learn to
swim. The river near the bottom of your garden affords a most convenient
place for the purpose. And as your new employment requires your being
often on the water, of which you have such a dread, I think you would do

well to make the trial; nothing being so likely to remove those
apprehensions as the consciousness of an ability to swim to the shore, in
case of an accident, or of supporting yourself in the water till a boat could
come to take you up.
I do not know how far corks or bladders may be useful in learning to
swim, having never seen much trial of them. Possibly they may be of
service in supporting the body while you are learning what is called the
stroke, or that manner of drawing in and striking out the hands and feet that
is necessary to produce progressive motion. But you will be no swimmer till
you can place some confidence in the power of the water to support you; I
would therefore advise the acquiring that confidence in the first place;
especially as I have known several who, by a little of the practice necessary
for that purpose, have insensibly acquired the stroke, taught as it were by
nature.
The practice I mean is this. Chusing a place where the water deepens
gradually, walk coolly into it till it is up to your breast, then turn round,
your face to the shore, and throw an egg into the water between you and the
shore. It will sink to the bottom, and be easily seen there, as your water is
clear. It must lie in water so deep as that you cannot reach it to take it up but
by diving for it. To encourage yourself in order to do this, reflect that your
progress will be from deeper to shallower water, and that at any time you
may, by bringing your legs under you and standing on the bottom, raise
your head far above the water. Then plunge under it with your eyes open,
throwing yourself towards the egg, and endeavouring by the action of your
hands and feet against the water to get forward till within reach of it. In this
attempt you will find, that the water buoys you up against your inclination;
that it is not so easy a thing to sink as you imagined; that you cannot but by
active force get down to the egg. Thus you feel the power of the water to
support you, and learn to confide in that power; while your endeavours to
overcome it, and to reach the egg, teach you the manner of acting on the
water with your feet and hands, which action is afterwards used in
swimming to support your head higher above water, or to go forward
through it.
I would the more earnestly press you to the trial of this method, because,
though I think I satisfied you that your body is lighter than water, and that
you might float in it a long time with your mouth free for breathing, if you

would put yourself in a proper posture, and would be still and forbear
struggling; yet till you have obtained this experimental confidence in the
water, I cannot depend on your having the necessary presence of mind to
recollect that posture and the directions I gave you relating to it. The
surprize may put all out of your mind. For though we value ourselves on
being reasonable knowing creatures, reason and knowledge seem on such
occasions to be of little use to us; and the brutes to whom we allow scarce a
glimmering of either, appear to have the advantage of us.
I will, however, take this opportunity of repeating, those particulars to
you, which I mentioned in our last conversation, as, by perusing them at
your leisure, you may possibly imprint them so in your memory as on
occasion to be of some use to you.
1. That though the legs, arms, and head, of a human body, being solid
parts, are specifically something heavier than fresh water, yet the trunk,
particularly the upper part, from its hollowness, is so much lighter than
water, as that the whole of the body taken together is too light to sink
wholly under water, but some part will remain above, until the lungs
become filled with water, which happens from drawing water into them
instead of air, when a person in the fright attempts breathing while the
mouth and nostrils are under water.
2. That the legs and arms are specifically lighter than salt water, and will
be supported by it, so that a human body would not sink in salt-water,
though the lungs were filled as above, but from the greater specific gravity
of the head.
3. That therefore a person throwing himself on his back in salt water, and
extending his arms, may easily lie so as to keep his mouth and nostrils free
for breathing; and by a small motion of his hands may prevent turning, if he
should perceive any tendency to it.
4. That in fresh water, if a man throws himself on his back, near the
surface, he cannot long continue in that situation but by proper action of his
hands on the water. If he uses no such action, the legs and lower part of the
body will gradually sink till he comes into an upright position, in which he
will continue suspended, the hollow of the breast keeping the head
uppermost.

5. But if, in this erect position, the head is kept upright above the
shoulders, as when we stand on the ground, the immersion will, by the
weight of that part of the head that is out of water, reach above the mouth
and nostrils, perhaps a little above the eyes, so that a man cannot long
remain suspended in water with his head in that position.
6. The body continuing suspended as before, and upright, if the head be
leaned quite back, so that the face looks upwards, all the back part of the
head being then under water, and its weight consequently in a great measure
supported by it, the face will remain above water quite free for breathing,
will rise an inch higher every inspiration, and sink as much every
expiration, but never so low as that the water may come over the mouth.
7. If therefore a person unacquainted with swimming and falling
accidentally into the water, could have presence of mind sufficient to avoid
struggling and plunging, and to let the body take this natural position, he
might continue long safe from drowning till perhaps help would come. For
as to the cloaths, their additional weight while immersed is very
inconsiderable, the water supporting it though, when he comes out of the
water, he would find them very heavy indeed.
But, as I said before, I would not advise you or any one to depend on
having this presence of mind on such an occasion, but learn fairly to swim;
as I wish all men were taught to do in their youth; they would, on many
occurrences, be the safer for having that skill, and on many more the
happier, as freer from painful apprehensions of danger, to say nothing of the
enjoyment in so delightful and wholesome an exercise. Soldiers particularly
should, methinks, all be taught to swim; it might be of frequent use either in
surprising an enemy, or saving themselves. And if I had now boys to
educate, I should prefer those schools (other things being equal) where an
opportunity was afforded for acquiring so advantageous an art, which once
learned is never forgotten.
I am, Sir, &c.
B. FRANKLIN.

FOOTNOTE:

[36] Oliver Neale. Editor.

O N T H E S A M E S U B J E C T,

In Answer to some Enquiries of M. Dubourg[37].

**** I am apprehensive that I shall not be able to find leisure for making
all the disquisitions and experiments which would be desirable on this
subject. I must, therefore, content myself with a few remarks.
The specific gravity of some human bodies, in comparison to that of
water, has been examined by Mr. Robinson, in our Philosophical
Transactions, volume 50, page 30, for the year 1757. He asserts, that fat
persons with small bones float most easily upon the water.
The diving-bell is accurately described in our Transactions.
When I was a boy, I made two oval pallets, each about ten inches long,
and six broad, with a hole for the thumb, in order to retain it fast in the palm
of my hand. They much resembled a painter's pallets. In swimming I
pushed the edges of these forward, and I struck the water with their flat
surfaces as I drew them back. I remember I swam faster by means of these
pallets, but they fatigued my wrists. I also fitted to the soles of my feet a
kind of sandals; but I was not satisfied with them, because I observed that
the stroke is partly given by the inside of the feet and the ancles, and not
entirely with the soles of the feet.
We have here waistcoats for swimming, which are made of double sail-
cloth, with small pieces of cork quilted in between them.
I know nothing of the scaphandre of M. de la Chapelle.
I know by experience, that it is a great comfort to a swimmer, who has a
considerable distance to go, to turn himself sometimes on his back, and to
vary in other respects the means of procuring a progressive motion.
When he is seized with the cramp in the leg, the method of driving it
away is to give to the parts affected a sudden, vigorous and violent shock;
which he may do in the air as he swims on his back.

During the great heats of summer there is no danger in bathing, however
warm we may be, in rivers which have been thoroughly warmed by the sun.
But to throw oneself into cold spring water, when the body has been heated
by exercise in the sun, is an imprudence which may prove fatal. I once
knew an instance of four young men, who, having worked at harvest in the
heat of the day, with a view of refreshing themselves plunged into a spring
of cold water: two died upon the spot, a third the next morning, and the
fourth recovered with great difficulty. A copious draught of cold water, in
similar circumstances, is frequently attended with the same effect in North
America.
The exercise of swimming is one of the most healthy and agreeable in the
world. After having swam for an hour or two in the evening, one sleeps
coolly the whole night, even during the most ardent heat of summer.
Perhaps the pores being cleansed, the insensible perspiration increases and
occasions this coolness. It is certain that much swimming is the means of
stopping a diarrhœa, and even of producing a constipation. With respect to
those who do not know how to swim, or who are affected with a diarrhœa at
a season which does not permit them to use that exercise, a warm bath, by
cleansing and purifying the skin, is found very salutary, and often effects a
radical cure. I speak from my own experience, frequently repeated, and that
of others to whom I have recommended this.
You will not be displeased if I conclude these hasty remarks by informing
you, that as the ordinary method of swimming is reduced to the act of
rowing with the arms and legs, and is consequently a laborious and
fatiguing operation when the space of water to be crossed is considerable;
there is a method in which a swimmer may pass to great distances with
much facility, by means of a sail. This discovery I fortunately made by
accident, and in the following manner.
When I was a boy I amused myself one day with flying a paper kite; and
approaching the bank of a pond, which was near a mile broad, I tied the
string to a stake, and the kite ascended to a very considerable height above
the pond, while I was swimming. In a little time, being desirous of amusing
myself with my kite, and enjoying at the same time the pleasure of
swimming, I returned; and loosing from the stake the string with the little
stick which was fastened to it, went again into the water, where I found,
that, lying on my back and holding the stick in my hands, I was drawn

along the surface of the water in a very agreeable manner. Having then
engaged another boy to carry my clothes round the pond, to a place which I
pointed out to him on the other side, I began to cross the pond with my kite,
which carried me quite over without the least fatigue, and with the greatest
pleasure imaginable. I was only obliged occasionally to halt a little in my
course, and resist its progress, when it appeared that, by following too
quick, I lowered the kite too much; by doing which occasionally I made it
rise again. I have never since that time practised this singular mode of
swimming, though I think it not impossible to cross in this manner from
Dover to Calais. The packet-boat, however, is still preferable. ****
B. FRANKLIN.

FOOTNOTE:

[37] This and the four following extracts of letters to M. Dubourg, are re-
translated from the French edition of Dr. Franklin's works. Editor.

TO M. DUBOURG.

On the free Use of Air.

London, July 28, 1760.
**** I greatly approve the epithet which you give, in your letter of the
8th of June, to the new method of treating the small-pox, which you call the
tonic or bracing method; I will take occasion, from it, to mention a practice
to which I have accustomed myself. You know the cold bath has long been
in vogue here as a tonic; but the shock of the cold water has always
appeared to me, generally speaking, as too violent, and I have found it
much more agreeable to my constitution to bathe in another element, I mean
cold air. With this view I rise almost every morning, and sit in my chamber
without any clothes whatever, half an hour or an hour, according to the
season, either reading or writing. This practice is not in the least painful,
but, on the contrary, agreeable; and if I return to bed afterwards, before I

dress myself, as sometimes happens, I make a supplement to my night's rest
of one or two hours of the most pleasing sleep that can be imagined. I find
no ill consequences whatever resulting from it, and that at least it does not
injure my health, if it does not in fact contribute much to its preservation. I
shall therefore call it for the future a bracing or tonic bath. ****
B. FRANKLIN.

On the Causes of Colds.

March 10, 1773.
**** I shall not attempt to explain why damp clothes occasion colds,
rather than wet ones, because I doubt the fact; I imagine that neither the one
nor the other contribute to this effect, and that the causes of colds are totally
independent of wet and even of cold. I propose writing a short paper on this
subject, the first moment of leisure I have at my disposal. In the mean time I
can only say, that having some suspicions that the common notion, which
attributes to cold the property of stopping the pores and obstructing
perspiration, was ill founded, I engaged a young physician, who is making
some experiments with Sanctorius's balance, to estimate the different
proportions of his perspiration, when remaining one hour quite naked, and
another warmly clothed. He pursued the experiment in this alternate manner
for eight hours successively, and found his perspiration almost double
during those hours in which he was naked. ****
B. FRANKLIN.

Dr. Stark[38].

May 4, 1773.
**** The young physician whom I mentioned is dead, and all the notes
which he had left of his curious experiments are by some accident lost
between our friends Sir John Pringle and Dr. Huck (Saunders); but these
gentlemen, if the papers cannot be recovered, it is to be presumed, will
repeat the experiments themselves ****
B. FRANKLIN.

Dr. Lettsom.

London, August 30, 1769.
**** This letter will be forwarded to you by Dr. Lettsom, a young
American physician of much merit, and one of the peaceable sect of
Quakers: you will therefore at least regard him as a curiosity, even though
you should have embraced all the opinions of the majority of your
countrymen concerning these people ****
B. FRANKLIN.

FROM DR. ——[39] OF BOSTON, TO BENJAMIN FRANKLIN,
ESQ. OF PHILADELPHIA.

Respecting the Number of Deaths in Philadelphia by Inoculation.

Boston, Aug. 3, 1752.
Sir,
This comes to you on account of Dr. Douglass: he desired me to write to
you for what you know of the number that died of the inoculation in

Philadelphia, telling me he designed to write something on the small-pox
shortly. We shall both be obliged to you for a word on this affair.
The chief particulars of our visitation, you have in the public prints. But
the less degree of mortality than usual in the common way of infection,
seems chiefly owing to the purging method designed to prevent the
secondary fever; a method first begun and carried on in this town, and with
success beyond expectation. We lost one in eleven one-sixth, but had we
been experienced in this way, at the first coming of the distemper, probably
the proportion had been but one in thirteen or fourteen. In the year 1730 we
lost one in nine, which is more favourable than ever before with us. The
distemper pretty much the same then as now, but some circumstances not so
kind this time.
If there be any particulars which you want to know, please to signify
what they are, and I shall send them.
The number of our inhabitants decreases[40]. On a strict inquiry, the
overseers of the poor find but fourteen thousand one hundred and ninety
Whites, and one thousand five hundred and forty-four Blacks, including
those absent, on account of the small-pox, many of whom, it is probable,
will never return.
I pass this opportunity without any particulars of my old theme. One
thing, however, I must mention, which is, that perhaps my last letters
contained something that seemed to militate with your doctrine of the
Origin, &c. But my design was only to relate the phenomena as they
appeared to me. I have received so much light and pleasure from your
writings, as to prejudice me in favour of every thing from your hand, and
leave me only liberty to observe, and a power of dissenting when some
great probability might oblige me: and if at any time that be the case, you
will certainly hear of it.
I am, Sir, &c.

FOOTNOTES:

[38] The works of Dr. Stark, including the experiments alluded to, have since
been published. Editor.
[39] Dr. Perkins. Editor.
[40] Boston is an old town, and was formerly the seat of all the trade of the
country, that was carried on by sea. New towns, and ports, have, of late, divided
the trade with it, and diminished its inhabitants, though the inhabitants of the
country, in general, have greatly increased.

FROM BENJAMIN FRANKLIN, ESQ. OF PHILADELPHIA.

In Answer to the preceding.

Philadelphia, Aug. 13, 1752.
Sir,
I received your favour of the 3d instant. Some time last winter I procured
from one of our physicians an account of the number of persons inoculated
during the five visitations of the small-pox we have had in twenty-two
years; which account I sent to Mr. W. V. of your town, and have no copy. If
I remember right, the number exceeded eight hundred, and the deaths were
but four. I suppose Mr. V. will show you the account, if he ever received it.
Those four were all that our doctors allow to have died of the small-pox by
inoculation, though I think there were two more of the inoculated who died
of the distemper; but the eruptions appearing soon after the operation, it is
supposed they had taken the infection before, in the common way.
I shall be glad to see what Dr. Douglass may write on the subject. I have
a French piece printed at Paris, 1724, entitled, Observations sur la Saignée
du Pied, et sur la Purgation au commencement de la Petite Verole, &
Raisons de doubte contre l' Inoculation.—A letter of the doctor's is
mentioned in it. If he or you have it not, and desire to see it, I will send it.—
Please to favour me with the particulars of your purging method, to prevent
the secondary fever.
I am indebted for your preceding letter, but business sometimes obliges
one to postpone philosophical amusements. Whatever I have wrote of that
kind, are really, as they are entitled, but Conjectures and Suppositions;
which ought always to give place, when careful observation militates

against them. I own I have too strong a penchant to the building of
hypotheses; they indulge my natural indolence: I wish I had more of your
patience and accuracy in making observations, on which, alone, true
philosophy can be founded. And, I assure you, nothing can be more
obliging to me, than your kind communication of those you make, however
they may disagree with my pre-conceived notions.
I am sorry to hear that the number of your inhabitants decreases. I some
time since, wrote a small paper of Thoughts on the peopling of
Countries[41], which, if I can find, I will send you, to obtain your
sentiments. The favourable opinion you express of my writings, may, you
see, occasion you more trouble than you expected from,
Sir, yours, &c.
B. FRANKLIN.

FOOTNOTE:

[41] This paper will be found in a subsequent part of the present volume. Editor.

T O B E N J A M I N VA U G H A N , E S Q .

On the Effects of Lead upon the human Constitution.[42]

Philadelphia, July 31, 1786.
DEAR FRIEND,

I recollect that when I had last the pleasure of seeing you at
Southampton, now a twelvemonth since, we had some conversation on the
bad effects of lead taken inwardly; and that at your request I promised to
send you in writing a particular account of several facts I then mentioned to
you, of which you thought some good use might be made. I now sit down to
fulfil that promise.

The first thing I remember of this kind was a general discourse in Boston
when I was a boy, of a complaint from North Carolina against New-
England rum, that it poisoned their people, giving them the dry-belly-ach,
with a loss of the use of their limbs. The distilleries being examined on the
occasion, it was found, that several of them used leaden still-heads and
worms, and the physicians were of opinion, that the mischief was
occasioned by that use of lead. The legislature of Massachussetts thereupon
passed an act, prohibiting, under severe penalties, the use of such still-heads
and worms hereafter.
In 1724, being in London, I went to work in the printing-house of Mr.
Palmer, Bartholomew-close, as a compositor. I there found a practice, I had
never seen before, of drying a case of types (which are wet in distribution)
by placing it sloping before the fire. I found this had the additional
advantage, when the types were not only dried but heated, of being
comfortable to the hands working over them in cold weather. I therefore
sometimes heated my case when the types did not want drying. But an old
workman observing it advised me not to do so, telling me I might lose the
use of my hands by it, as two of our companions had nearly done, one of
whom, that used to earn his guinea a week, could not then make more than
ten shillings, and the other, who had the dangles, but seven and sixpence.
This, with a kind of obscure pain, that I had sometimes felt, as it were, in
the bones of my hand when working over the types made very hot, induced
me to omit the practice. But talking afterwards with Mr. James, a letter-
founder in the same Close, and asking him if his people, who worked over
the little furnaces of melted metal, were not subject to that disorder; he
made light of any danger from the effluvia, but ascribed it to particles of the
metal swallowed with their food by slovenly workmen, who went to their
meals after handling the metal, without well washing their fingers, so that
some of the metalline particles were taken off by their bread and eaten with
it. This appeared to have some reason in it. But the pain I had experienced
made me still afraid of those effluvia.
Being in Derbyshire at some of the furnaces for smelting of lead ore, I
was told, that the smoke of those furnaces was pernicious to the
neighbouring grass and other vegetables; but I do not recollect to have
heard any thing of the effect of such vegetables eaten by animals. It may be
well to make the enquiry.

In America I have often observed, that on the roofs of our shingled-
houses, where moss is apt to grow in northern exposures, if there be any
thing on the roof painted with white lead, such as balusters, or frames of
dormant windows, &c. there is constantly a streak on the shingles from
such paint down to the eaves, on which no moss will grow, but the wood
remains constantly clean and free from it. We seldom drink rain-water that
fall on our houses; and if we did, perhaps the small quantity of lead
descending from such paint might not be sufficient to produce any sensible
ill-effect on our bodies. But I have been told of a case in Europe, I forget
the place, where a whole family was afflicted with what we call the dry-
belly-ach, or colica pictorum, by drinking rain-water. It was at a country-
seat, which, being situated too high to have the advantage of a well, was
supplied with water from a tank, which received the water from the leaded
roofs. This had been drank several years without mischief, but some young
trees planted near the house growing up above the roof, and shedding their
leaves upon it, it was supposed, that an acid in those leaves had corroded
the lead they covered, and furnished the water of that year with its baneful
particles and qualities.
When I was in Paris with Sir John Pringle in 1767, he visited La Charité,
an hospital particularly famous for the cure of that malady, and brought
from thence a pamphlet, containing a list of the names of persons,
specifying their professions or trades, who had been cured there. I had the
curiosity to examine that list, and found, that all the patients were of trades,
that some way or other use or work in lead; such as plumbers, glaziers,
painters, &c. excepting only two kinds, stone-cutters and soldiers. In them,
I could not reconcile it to my notion, that lead was the cause of that
disorder. But on my mentioning it to a physician of that hospital, he
informed me, that the stone-cutters are continually using melted lead to fix
the ends of iron balustrades in stone; and that the soldiers had been
employed by painters as labourers in grinding of colours.
This, my dear friend, is all I can at present recollect on the subject. You
will see by it, that the opinion of this mischievous effect from lead, is at
least above sixty years old; and you will observe with concern how long a
useful truth may be known and exist, before it is generally received and
practised on.
I am, ever, yours most affectionately,

B. FRANKLIN.

FOOTNOTE:

[42] This letter is taken from a work by Dr. John Hunter, entitled Observations
on the Diseases of the Army. Editor.

TO M. DUBOURG[43].

Observations on the prevailing Doctrines of Life and Death.

**** Your observations on the causes of death, and the experiments
which you propose for recalling to life those who appear to be killed by
lightning, demonstrate equally your sagacity and your humanity. It appears,
that the doctrines of life and death, in general, are yet but little understood.
A toad buried in sand will live, it is said, till the sand becomes petrified:
and then, being inclosed in the stone, it may still live for we know not how
many ages. The facts which are cited in support of this opinion are too
numerous, and too circumstantial, not to deserve a certain degree of credit.
As we are accustomed to see all the animals, with which we are acquainted,
eat and drink, it appears to us difficult to conceive, how a toad can be
supported in such a dungeon: but if we reflect, that the necessity of
nourishment, which animals experience in their ordinary state, proceeds
from the continual waste of their substance by perspiration, it will appear
less incredible, that some animals in a torpid state, perspiring less because
they use no exercise, should have less need of aliment; and that others,
which are covered with scales or shells, which stop perspiration, such as
land and sea-turtles, serpents, and some species of fish, should be able to
subsist a considerable time without any nourishment whatever.—A plant,
with its flowers, fades and dies immediately, if exposed to the air without
having its root immersed in a humid soil, from which it may draw a
sufficient quantity of moisture to supply that which exhales from its
substance and is carried off continually by the air. Perhaps, however, if it
were buried in quicksilver, it might preserve for a considerable space of
time its vegetable life, its smell and colour. If this be the case, it might
prove a commodious method of transporting from distant countries those
delicate plants, which are unable to sustain the inclemency of the weather at
sea, and which require particular care and attention. I have seen an instance
of common flies preserved in a manner somewhat similar. They had been
drowned in Madeira wine, apparently about the time when it was bottled in
Virginia, to be sent hither (to London). At the opening of one of the bottles,

at the house of a friend where I then was, three drowned flies fell into the
first glass that was filled. Having heard it remarked, that drowned flies were
capable of being revived by the rays of the sun, I proposed making the
experiment upon these: they were therefore exposed to the sun upon a sieve,
which had been employed to strain them out of the wine. In less than three
hours, two of them began by degrees to recover life. They commenced by
some convulsive motions of the thighs, and at length they raised themselves
upon their legs, wiped their eyes with their fore-feet, beat and brushed their
wings with their hind-feet, and soon after began to fly, finding themselves
in Old England, without knowing how they came thither. The third
continued lifeless till sunset, when, losing all hopes of him, he was thrown
away.
I wish it were possible, from this instance, to invent a method of
embalming drowned persons, in such a manner that they may be recalled to
life at any period, however distant; for having a very ardent desire to see
and observe the state of America an hundred years hence, I should prefer to
any ordinary death, the being immersed in a cask of Madeira wine, with a
few friends till that time, to be then recalled to life by the solar warmth of
my dear country! But since in all probability we live in an age too early and
too near the infancy of science, to hope to see such an art brought in our
time to its perfection, I must for the present content myself with the treat,
which you are so kind as to promise me, of the resurrection of a fowl or a
turkey-cock.
I am, &c.
B. FRANKLIN.

FOOTNOTE:

[43] This letter is translated from the French edition of Dr. Franklin's works. It
has no date, but the letter to which it is an answer is dated 15th April, 1773.

An Account of the new-invented Pensylvanian Fire-Places:

wherein their Construction and Manner of Operation is particularly explained; their
Advantages above every other Method of warming Rooms demonstrated; and all
Objections that have been raised against the Use of them answered and obviated. With
Directions for putting them up, and for using them to the best Advantage. And a Copper-
Plate, in which the several parts of the Machine are exactly laid down, from a Scale of
Equal Parts.

BY B. FRANKLIN.
(First printed at Philadelphia in 1745.)

In these northern colonies the inhabitants keep fires to sit by generally
seven months in the year; that is, from the beginning of October, to the end
of April; and, in some winters, near eight months, by taking in part of
September and May.
Wood, our common fuel, which within these hundred years might be had
at every man's door, must now be fetched near one hundred miles to some
towns, and makes a very considerable article in the expence of families.
As therefore so much of the comfort and conveniency of our lives, for so
great a part of the year, depends on the article of fire; since fuel is become
so expensive, and (as the country is more cleared and settled) will of course
grow scarcer and dearer, any new proposal for saving the wood, and for
lessening the charge, and augmenting the benefit of fire, by some particular
method of making and managing it, may at least be thought worth
consideration.
The new fire-places are a late invention to that purpose, of which this
paper is intended to give a particular account.
That the reader may the better judge whether this method of managing
fire has any advantage over those heretofore in use, it may be proper to
consider both the old and new methods separately and particularly, and
afterwards make the comparison.
In order to this, it is necessary to understand well, some few of the
properties of air and fire, viz.
1. Air is rarefied by heat, and condensed by cold, i. e. the same quantity
of air takes up more space when warm than when cold. This may be shown
by several very easy experiments. Take any clear glass bottle (a Florence

flask stript of the straw is best) place it before the fire, and as the air within
is warmed and rarefied, part of it will be driven out of the bottle; turn it up,
place its mouth in a vessel of water, and remove it from the fire; then, as the
air within cools and contracts, you will see the water rise in the neck of the
bottle, supplying the place of just so much air as was driven out. Hold a
large hot coal near the side of the bottle, and as the air within feels the heat,
it will again distend and force out the water.—Or, fill a bladder not quite
full of air, tie the neck tight, and lay it before a fire as near as may be
without scorching the bladder; as the air within heats, you will perceive it to
swell and fill the bladder, till it becomes tight, as if full blown: remove it to
a cool place, and you will see it fall gradually, till it becomes as lank as at
first.
2. Air rarefied and distended by heat is[44] specifically
lighter than it was before, and will rise in other air of greater density. As
wood, oil, or any other matter specifically lighter than water, if placed at the
bottom of a vessel of water, will rise till it comes to the top; so rarefied air
will rise in common air, till it either comes to air of equal weight, or is by
cold reduced to its former density.
A fire then being made in any chimney, the air over the fire is rarefied by
the heat, becomes lighter, and therefore immediately rises in the funnel, and
goes out; the other air in the room (flowing towards the chimney) supplies
its place, is rarefied in its turn, and rises likewise; the place of the air thus
carried out of the room, is supplied by fresh air coming in through doors
and windows, or, if they be shut, through every crevice with violence, as
may be seen by holding a candle to a key-hole: If the room be so tight as
that all the crevices together will not supply so much air as is continually
carried off, then, in a little time, the current up the funnel must flag, and the
smoke being no longer driven up, must come into the room.
1. Fire (i. e. common fire) throws out light, heat, and smoke (or fume.)
The two first move in right lines, and with great swiftness, the latter is but
just separated from the fuel, and then moves only as it is carried by the
stream of rarefied air: and without a continual accession and recession of
air, to carry off the smoaky fumes, they would remain crouded about the
fire, and stifle it.

2. Heat may be separated from the smoke as well as from the light, by
means of a plate of iron, which will suffer heat to pass through it without
the others.
3. Fire sends out its rays of heat as well as rays of light, equally every
way; but the greatest sensible heat is over the fire, where there is, besides
the rays of heat shot upwards, a continual rising stream of hot air, heated by
the rays shot round on every side.
These things being understood, we proceed to consider the fire-places
heretofore in use, viz.
1. The large open fire-places used in the days of our fathers, and still
generally in the country, and in kitchens.
2. The newer-fashioned fire-places, with low breasts, and narrow hearths.
3. Fire-places with hollow backs, hearths, and jams of iron (described by
M. Gauger, in his tract entitled, La Mechanique de Feu) for warming the air
as it comes into the room.
4. The Holland stoves, with iron doors opening into the room.
5. The German stoves, which have no opening in the room where they
are used, but the fire is put in from some other room, or from without.
6. Iron pots, with open charcoal fires, placed in the middle of a room.
1. The first of these methods has generally the conveniency of two warm
seats, one in each corner; but they are sometimes too hot to abide in, and, at
other times, incommoded with the smoke; there is likewise good room for
the cook to move, to hang on pots, &c. Their inconveniencies are, that they
almost always smoke, if the door be not left open; that they require a large
funnel, and a large funnel carries off a great quantity of air, which occasions
what is called a strong draft to the chimney, without which strong draft the
smoke would come out of some part or other of so large an opening, so that
the door can seldom be shut; and the cold air so nips the backs and heels of
those that sit before the fire, that they have no comfort till either screens or
settles are provided (at a considerable expence) to keep it off, which both
cumber the room, and darken the fire-side. A moderate quantity of wood on
the fire, in so large a hearth, seems but little; and, in so strong and cold a
draught, warms but little; so that people are continually laying on more. In

short, it is next to impossible to warm a room with such a fire-place: and I
suppose our ancestors never thought of warming rooms to sit in; all they
purposed was, to have a place to make a fire in, by which they might warm
themselves when cold.
2. Most of these old-fashioned chimneys in towns and cities, have been,
of late years, reduced to the second sort mentioned, by building jambs
within them, narrowing the hearth, and making a low arch or breast. It is
strange, methinks, that though chimneys have been so long in use, their
construction should be so little understood till lately, that no workman
pretended to make one which should always carry off all smoke, but a
chimney-cloth was looked upon as essential to a chimney. This
improvement, however, by small openings and low breasts, has been made
in our days; and success in the first experiments has brought it into general
use in cities, so that almost all new chimneys are now made of that sort, and
much fewer bricks will make a stack of chimneys now than formerly. An
improvement, so lately made, may give us room to believe, that still farther
improvements may be found to remedy the inconveniencies yet remaining.
For these new chimneys, though they keep rooms generally free from
smoke, and, the opening being contracted, will allow the door to be shut,
yet the funnel still requiring a considerable quantity of air, it rushes in at
every crevice so strongly, as to make a continual whistling or howling; and
it is very uncomfortable, as well as dangerous, to sit against any such
crevice. Many colds are caught from this cause only, it being safer to sit in
the open street, for then the pores do all close together, and the air does not
strike so sharply against any particular part of the body.
The Spaniards have a proverbial saying,
If the wind blows on you through a hole,
Make your will, and take care of your soul.

Women particularly, from this cause, as they sit much in the house, get
colds in the head, rheums and defluctions, which fall into their jaws and
gums, and have destroyed early many a fine set of teeth in these northern
colonies. Great and bright fires do also very much contribute to damage the
eyes, dry and shrivel the skin, and bring on early the appearances of old
age. In short, many of the diseases proceeding from colds, as fevers,
pleurisies, &c. fatal to very great numbers of people, may be ascribed to
strong drawing chimneys, whereby, in severe weather, a man is scorched

before while he is froze behind.[45] In the mean time, very little is done by
these chimneys towards warming the room; for the air round the fire-place,
which is warmed by the direct rays from the fire, does not continue in the
room, but is continually crouded and gathered into the chimney by the
current of cold air coming behind it, and so is presently carried off.
In both these sorts of fire-places, the greatest part of the heat from the fire
is lost; for as fire naturally darts heat every way, the back, the two jambs,
and the hearth, drink up almost all that is given them, very little being
reflected from bodies so dark, porous, and unpolished; and the upright heat,
which is by far the greatest, flies directly up the chimney. Thus five-sixths
at least of the heat (and consequently of the fuel) is wasted, and contributes
nothing towards warming the room.
3. To remedy this, the Sieur Gauger gives, in his book entitled, La
Mechanique de Feu, published in 1709, seven different constructions of the
third sort of chimneys mentioned above, in which there are hollow cavities
made by iron plates in the back, jambs, and hearths, through which plates
the heat passing warms the air in those cavities, which is continually
coming into the room fresh and warm. The invention was very ingenious,
and had many conveniencies: the room was warmed in all parts, by the air
flowing into it through the heated cavities: cold air was prevented rushing
through the crevices, the funnel being sufficiently supplied by those
cavities: much less fuel would serve, &c. But the first expence, which was
very great, the intricacy of the design, and the difficulty of the execution,
especially in old chimneys, discouraged the propagation of the invention; so
that there are, I suppose, very few such chimneys now in use. [The upright
heat, too, was almost all lost in these, as in the common chimneys.]
4. The Holland iron stove, which has a flue proceeding from the top, and
a small iron door opening into the room, comes next to be considered. Its
conveniencies are, that it makes a room all over warm; for the chimney
being wholly closed, except the flue of the stove, very little air is required
to supply that, and therefore not much rushes in at crevices, or at the door
when it is opened. Little fuel serves, the heat being almost all saved; for it
rays out almost equally from the four sides, the bottom and the top, into the
room, and presently warms the air around it, which, being rarefied, rises to
the ceiling, and its place is supplied by the lower air of the room, which
flows gradually towards the stove, and is there warmed, and rises in its turn,

so that there is a continual circulation till all the air in the room is warmed.
The air, too, is gradually changed, by the stove-door's being in the room,
through which part of it is continually passing, and that makes these stoves
wholesomer, or at least pleasanter than the German stoves, next to be
spoken of. But they have these inconveniencies. There is no sight of the
fire, which is in itself a pleasant thing. One cannot conveniently make any
other use of the fire but that of warming the room. When the room is warm,
people, not seeing the fire, are apt to forget supplying it with fuel till it is
almost out, then, growing cold, a great deal of wood is put in, which soon
makes it too hot. The change of air is not carried on quite quick enough, so
that if any smoke or ill smell happens in the room, it is a long time before it
is discharged. For these reasons the Holland stove has not obtained much
among the English (who love the sight of the fire) unless in some
workshops, where people are obliged to sit near windows for the light, and
in such places they have been found of good use.
5. The German stove is like a box, one side wanting. It is composed of
five iron plates screwed together, and fixed so as that you may put the fuel
into it from another room, or from the outside of the house. It is a kind of
oven reversed, its mouth being without, and body within the room that is to
be warmed by it. This invention certainly warms a room very speedily and
thoroughly with little fuel: no quantity of cold air comes in at any crevice,
because there is no discharge of air which it might supply, there being no
passage into the stove from the room. These are its conveniencies. Its
inconveniencies are, that people have not even so much sight or use of the
fire as in the Holland stoves, and are, moreover, obliged to breathe the same
unchanged air continually, mixed with the breath and perspiration from one
another's bodies, which is very disagreeable to those who have not been
accustomed to it.

Plate VIII. Vol. II. page 235.

View larger image here
Published as the Act directs, April 1, 1806, by Longman, Hurst, Rees & Orme, Paternoster Row.

6. Charcoal fires in pots are used chiefly in the shops of handicraftsmen.
They warm a room (that is kept close, and has no chimney to carry off the
warmed air) very speedily and uniformly; but there being no draught to
change the air, the sulphurous fumes from the coals [be they ever so well
kindled before they are brought in, there will be some] mix with it, render it
disagreeable, hurtful to some constitutions, and sometimes, when the door
is long kept shut, produce fatal consequences.
To avoid the several inconveniencies, and at the same time retain all the
advantages of other fire-places, was contrived the Pensylvania fire-place,
now to be described.

This machine consists of
A bottom-plate, (i) (See the Plate annexed.)
A back plate, (ii)
Two side plates, (iii iii)
Two middle plates, (iv iv) which, joined together, form a tight box, with
winding passages in it for warming the air.
A front plate, (v)
A top plate (vi)
These are all cast of iron, with mouldings or ledges where the plates
come together, to hold them fast, and retain the mortar used for pointing to
make tight joints. When the plates are all in their places, a pair of slender
rods, with screws, are sufficient to bind the whole very firmly together, as it
appears in Fig. 2.
There are, moreover, two thin plates of wrought iron, viz. the shutter,
(vii) and the register, (viii); besides the screw-rods O P, all which we shall
explain in their order.
(i) The bottom plate, or hearth-piece, is round before, with a rising
moulding, that serves as a fender to keep coals and ashes from coming to
the floor, &c. It has two ears, F G, perforated to receive the screw-rods O P;
a long air-hole, a a, through which the fresh outward air passes up into the
air-box; and three smoke-holes B C, through which the smoke descends and
passes away; all represented by dark squares. It has also double ledges to
receive between them the bottom edges of the back plate, the two side-
plates, and the two middle plates. These ledges are about an inch asunder,
and about half an inch high; a profile of two of them, joined to a fragment
of plate, appears in Fig. 3.
(ii) The back plate is without holes, having only a pair of ledges on each
side, to receive the back edges of the two.
(iii iii) Side-plates: These have each a pair of ledges to receive the side-
edges of the front-plate, and a little shoulder for it to rest on; also two pair
of ledges to receive the side-edges of the two middle plates which form the
air-box; and an oblong air-hole near the top, through which is discharged

into the room the air warmed in the air-box. Each has also a wing or
bracket, H and I, to keep in falling brands, coals, &c. and a small hole, Q
and R, for the axis of the register to turn in.
(iv iv) The air-box is composed of the two middle plates, D E and F G.
The first has five thin ledges or partitions cast on it, two inches deep, the
edges of which are received in so many pair of ledges cast in the other. The
tops of all the cavities formed by these thin deep ledges, are also covered by
a ledge of the same form and depth, cast with them; so that when the plates
are put together, and the joints luted, there is no communication between
the air-box and the smoke. In the winding passages of this box, fresh air is
warmed as it passes into the room.
(v) The front plate is arched on the under side, and ornamented with
foliages, &c. it has no ledges.
(vi) The top plate has a pair of ears, M N, answerable to those in the
bottom plate, and perforated for the same purpose: it has also a pair of
ledges running round the under side, to receive the top edges of the front,
back, and side-plates. The air-box does not reach up to the top plate by two
inches and a half.
(vii) The shutter is of thin wrought iron and light, of such a length and
breadth as to close well the opening of the fire-place. It is used to blow up
the fire, and to shut up and secure it at nights. It has two brass knobs for
handles, d d, and commonly slides up and down in a groove, left, in putting
up the fire-place, between the foremost ledge of the side-plates, and the face
of the front plate; but some chuse to set it aside when it is not in use, and
apply it on occasion.
(viii) The register is also of thin wrought iron. It is placed between the
back plate and air-box, and can, by means of the key S, be turned on its axis
so as to lie in any position between level and upright.
The screw-rods O P are of wrought iron, about a third of an inch thick,
with a button at bottom, and a screw and nut at top, and may be ornamented
with two small brasses screwed on above the nuts.
To put this machine to work,
1. A false back of four inch (or, in shallow small chimneys, two inch)
brick work is to be made in the chimney, four inches or more from the true

back; from the top of this false back a closing is to be made over to the
breast of the chimney, that no air may pass into the chimney, but what goes
under the false back, and up behind it.
2. Some bricks of the hearth are to be taken up, to form a hollow under
the bottom plate; across which hollow runs a thin tight partition, to keep
apart the air entering the hollow and the smoke; and is therefore placed
between the air-hole and smoke-holes.
3. A passage is made, communicating with the outward air, to introduce
that air into the fore part of the hollow under the bottom plate, whence it
may rise through the air-hole into the air-box.
4. A passage is made from the back part of the hollow, communicating
with the flue behind the false back: through this passage the smoke is to
pass.
The fire-place is to be erected upon these hollows, by putting all the
plates in their places, and screwing them together.
Its operation may be conceived by observing the plate entitled, Profile of
the Chimney and Fire-Place.
M The mantle-piece, or breast of the chimney.
C The funnel.
B The false back and closing.
E True back of the chimney.
T Top of the fire-place.
F The front of it.
A The place where the fire is made.
D The air-box.
K The hole in the side-plate, through which the warmed air is discharged
out of the air-box into the room.
H The hollow filled with fresh air, entering at the passage I, and
ascending into the air-box through the air-hole in the bottom plate near
G The partition in the hollow to keep the air and smoke apart.

P The passage under the false back and part of the hearth for the smoke.
The arrows show the course of the smoke.

Plate VIII*. Vol. II. page 238.

Profile of the Pensylvania Chimney & Fire-Place.

Front View Staffordshire Fire-Place. Side View

Published as the Act directs, April 1, 1806, by Longman, Hurst, Rees & Orme, Paternoster Row.

The fire being made at A, the flame and smoke will ascend and strike the
top T, which will thereby receive a considerable heat. The smoke, finding
no passage upwards, turns over the top of the air-box, and descends
between it and the back plate to the holes in the bottom plate, heating, as it
passes, both plates of the air-box, and the said back plate; the front plate,
bottom and side plates are also all heated at the same time. The smoke
proceeds in the passage that leads it under and behind the false back, and so
rises into the chimney. The air of the room, warmed behind the back plate,
and by the sides, front, and top plates, becoming specifically lighter than the
other air in the room, is obliged to rise; but the closure over the fireplace
hindering it from going up the chimney, it is forced out into the room, rises
by the mantle-piece to the cieling, and spreads all over the top of the room,
whence being crouded down gradually by the stream of newly-warmed air
that follows and rises above it, the whole room becomes in a short time
equally warmed.
At the same time the air, warmed under the bottom plate, and in the air-
box, rises and comes out of the holes in the side-plates, very swiftly, if the
door of the room be shut, and joins its current with the stream before-
mentioned, rising from the side, back, and top plates.
The air that enters the room through the air-box is fresh, though warm;
and, computing the swiftness of its motion with the areas of the holes, it is
found that near ten barrels of fresh air are hourly introduced by the air-box;
and by this means the air in the room is continually changed, and kept, at
the same time, sweet and warm.
It is to be observed, that the entering air will not be warm at first lighting
the fire, but heats gradually as the fire increases.
A square opening for a trap-door should be left in the closing of the
chimney, for the sweeper to go up: the door may be made of slate or tin, and
commonly kept close shut, but so placed as that, turning up against the back
of the chimney when open, it closes the vacancy behind the false back, and
shoots the soot, that falls in sweeping, out upon the hearth. This trap-door is
a very convenient thing.

In rooms where much smoking of tobacco is used, it is also convenient to
have a small hole, about five or six inches square, cut near the ceiling
through into the funnel: this hole must have a shutter, by which it may be
closed or opened at pleasure. When open, there will be a strong draught of
air through it into the chimney, which will presently carry off a cloud of
smoke, and keep the room clear: if the room be too hot like-wise, it will
carry off as much of the warm air as you please, and then you may stop it
entirely, or in part, as you think fit. By this means it is, that the tobacco
smoke does not descend among the heads of the company near the fire, as it
must do before it can get into common chimneys.

The Manner of using this Fire-Place.
Your cord-wood must be cut into three lengths; or else a short piece, fit
for the fire-place, cut off, and the longer left for the kitchen or other fires.
Dry hickery, or ash, or any woods that burn with a clear flame are rather to
be chosen, because such are less apt to foul the smoke-passages with soot;
and flame communicates with its light, as well as by contact, greater heat to
the plates and room. But where more ordinary wood is used, half a dry
faggot of brush-wood, burnt at the first making the fire in the morning, is
very advantageous, as it immediately, by its sudden blaze, heats the plates,
and warms the room (which with bad wood slowly kindling would not be
done so soon) and at the same time by the length of its flame, turning in the
passages, consumes and cleanses away the soot that such bad smoaky wood
had produced therein the preceding day, and so keeps them always free and
clean. When you have laid a little back log, and placed your billets on small
dogs, as in common chimneys, and put some fire to them, then slide down
your shutter as low as the dogs, and the opening being by that means
contracted, the air rushes in briskly, and presently blows up the flames.
When the fire is sufficiently kindled, slide it up again.[46] In some of these
fire-places there is a little six-inch square trap-door of thin wrought iron or
brass, covering a hole of like dimensions near the fore-part of the bottom
plate, which being by a ring lifted up towards the fire, about an inch, where
it will be retained by two springing sides fixed to it perpendicularly (See the
Plate, Fig. 4.) the air rushes in from the hollow under the bottom plate, and
blows the fire. Where this is used, the shutter serves only to close the fire at
nights. The more forward you can make your fire on the hearth-plate, not to

be incommoded by the smoke, the sooner and more will the room be
warmed. At night, when you go to bed, cover the coals or brands with ashes
as usual; then take away the dogs, and slide down the shutter close to the
bottom-plate, sweeping a little ashes against it, that no air may pass under
it; then turn the register, so as very near to stop the flue behind. If no smoke
then comes out at crevices into the room, it is right: if any smoke is
perceived to come out, move the register, so as to give a little draught, and
it will go the right way. Thus the room will be kept warm all night; for the
chimney being almost entirely stopt, very little cold air, if any, will enter the
room at any crevice. When you come to re-kindle the fire in the morning,
turn open the register before you lift up the slider, otherwise, if there be any
smoke in the fireplace, it will come out into the room. By the same use of
the shutter and register, a blazing fire may be presently stifled, as well as
secured, when you have occasion to leave it for any time; and at your return
you will find the brands warm, and ready for a speedy rekindling. The
shutter alone will not stifle a fire, for it cannot well be made to fit so exactly
but that air will enter, and that in a violent stream, so as to blow up and
keep alive the flames, and consume the wood, if the draught be not checked
by turning the register to shut the flue behind. The register has also two
other uses. If you observe the draught of air into your fire-place to be
stronger than is necessary (as in extreme cold weather it often is) so that the
wood is consumed faster than usual; in that case, a quarter, half, or two-
thirds turn of the register, will check the violence of the draught, and let
your fire burn with the moderation you desire: and at the same time both the
fire-place and the room will be the warmer, because less cold air will enter
and pass through them. And if the chimney should happen to take fire
(which indeed there is very little danger of, if the preceding direction be
observed in making fires, and it be well swept once a year; for, much less
wood being burnt, less soot is proportionably made; and the fuel being soon
blown into flame by the shutter, or the trap-door bellows, there is
consequently less smoke from the fuel to make soot; then, though the funnel
should be foul, yet the sparks have such a crooked up and down round
about way to go, that they are out before they get at it). I say, if ever it
should be on fire, a turn of the register shuts all close, and prevents any air
going into the chimney, and so the fire may easily be stifled and mastered.

The Advantages of this Fire-Place.

Its advantages above the common fire-places are,
1. That your whole room is equally warmed, so that people need not
croud so close round the fire, but may sit near the window, and have the
benefit of the light for reading, writing, needle-work, &c. They may sit with
comfort in any part of the room, which is a very considerable advantage in a
large family, where there must often be two fires kept, because all cannot
conveniently come at one.
2. If you sit near the fire, you have not that cold draught of
uncomfortable air nipping your back and heels, as when before common
fires, by which many catch cold, being scorched before, and, as it were,
froze behind.
3. If you sit against a crevice, there is not that sharp draught of cold air
playing on you, as in rooms where there are fires in the common way; by
which many catch cold, whence proceed coughs[47], catarrhs, tooth-achs,
fevers, pleurisies, and many other diseases.
4. In case of sickness, they make most excellent nursing rooms; as they
constantly supply a sufficiency of fresh air, so warmed at the same time as
to be no way inconvenient or dangerous. A small one does well in a
chamber; and, the chimneys, being fitted for it, it may be removed from one
room to another, as occasion requires, and fixed in half an hour. The equal
temper too, and warmth of the air of the room, is thought to be particularly
advantageous in some distempers; for it was observed in the winters of
1730 and 1736, when the small-pox spread in Pensylvania, that very few
children of the Germans died of that distemper in proportion to those of the
English; which was ascribed, by some, to the warmth and equal temper of
air in their stove-rooms, which made the disease as favourable as it
commonly is in the West Indies. But this conjecture we submit to the
judgment of physicians.
5. In common chimneys, the strongest heat from the fire, which is
upwards, goes directly up the chimney, and is lost; and there is such a
strong draught into the chimney that not only the upright heat, but also the
back, sides, and downward heats are carried up the chimney by that draught
of air; and the warmth given before the fire, by the rays that strike out
towards the room, is continually driven back, crouded into the chimney, and
carried up by the same draught of air. But here the upright heat strikes and

heats the top plate, which warms the air above it, and that comes into the
room. The heat likewise, which the fire communicates to the sides, back,
bottom, and air-box, is all brought into the room; for you will find a
constant current of warm air coming out of the chimney-corner into the
room. Hold a candle just under the mantle-piece, or breast of your chimney,
and you will see the flame bent outwards: by laying a piece of smoaking
paper on the hearth, on either side, you may see how the current of air
moves, and where it tends, for it will turn and carry the smoke with it.
6. Thus, as very little of the heat is lost, when this fire-place is used,
much less wood[48] will serve you, which is a considerable advantage where
wood is dear.
7. When you burn candles near this fire-place, you will find that the
flame burns quite upright, and does not blare and run the tallow down, by
drawing towards the chimney, as against common fires.
8. This fire-place cures most smoaky chimneys, and thereby preserves
both the eyes and furniture.
9. It prevents the fouling of chimneys; much of the lint and dust that
contributes to foul a chimney being, by the low arch, obliged to pass
through the flame, where it is consumed. Then, less wood being burnt, there
is less smoke made. Again, the shutter, or trap-bellows, soon blowing the
wood into a flame, the same wood does not yield so much smoke as if burnt
in a common chimney: for as soon as flame begins, smoke in proportion
ceases.
10. And if a chimney should be foul, it is much less likely to take fire. If
it should take fire, it is easily stifled and extinguished.
11. A fire may be very speedily made in this fire-place by the help of the
shutter, or trap-bellows, as aforesaid.
12. A fire may be soon extinguished, by closing it with the shutter before,
and turning the register behind, which will stifle it, and the brands will
remain ready to rekindle.
13. The room being once warm, the warmth may be retained in it all
night.

14. And lastly, the fire is so secured at night, that not one spark can fly
out into the room to do damage.
With all these conveniences, you do not lose the pleasing sight nor use of
the fire, as in the Dutch stoves, but may boil the tea-kettle, warm the flat-
irons, heat heaters, keep warm a dish of victuals by setting it on the top, &c.

Objections answered.
There are some objections commonly made by people that are
unacquainted with these fire-places, which it may not be amiss to
endeavour to remove, as they arise from prejudices which might otherwise
obstruct, in some degree, the general use of this beneficial machine. We
frequently hear it said, They are of the nature of Dutch stoves; stoves have
an unpleasant smell; stoves are unwholesome; and, warm rooms make
people tender, and apt to catch cold.—As to the first, that they are of the
nature of Dutch stoves, the description of those stoves, in the beginning of
this paper, compared with that of these machines, shows that there is a most
material difference, and that these have vastly the advantage, if it were only
in the single article of the admission and circulation of the fresh air. But it
must be allowed there may have been some cause to complain of the
offensive smell of iron stoves. This smell, however, never proceeded from
the iron itself, which, in its nature, whether hot or cold, is one of the
sweetest of metals, but from the general uncleanly manner of using those
stoves. If they are kept clean, they are as sweet as an ironing-box, which
though ever so hot, never offends the smell of the nicest lady: but it is
common to let them be greased, by setting candlesticks on them, or
otherwise; to rub greasy hands on them; and, above all, to spit upon them,
to try how hot they are, which is an inconsiderate filthy unmannerly
custom; for the slimy matter of spittle drying on burns and fumes when the
stove is hot, as well as the grease, and smells most nauseously, which
makes such close stove-rooms, where there is no draught to carry off those
filthy vapours, almost intolerable to those that are not from their infancy
accustomed to them. At the same time nothing is more easy than to keep
them clean; for when by any accident they happen to be fouled, a lee made
of ashes and water, with a brush, will scour them perfectly: as will also a
little strong soft soap and water.

That hot iron of itself gives no offensive smell, those know very well
who have (as the writer of this has) been present at a furnace when the
workmen were pouring out the flowing metal to cast large plates, and not
the least smell of it to be perceived. That hot iron does not, like lead, brass,
and some other metals, give out unwholesome vapours, is plain from the
general health and strength of those who constantly work in iron, as
furnace-men, forge-men, and smiths; that it is in its nature a metal perfectly
wholesome to the body of man, is known from the beneficial use of
chalybeate or iron-mine-waters; from the good done by taking steel filings
in several disorders; and that even the smithy water in which hot irons are
quenched, is found advantageous to the human constitution.—The
ingenious and learned Dr. Desaguliers, to whose instructive writings the
contriver of this machine acknowledges himself much indebted, relates an
experiment he made, to try whether heated iron would yield unwholesome
vapours: he took a cube of iron, and having given it a very great heat, he
fixed it so to a receiver, exhausted by the air-pump, that all the air rushing
in to fill the receiver, should first pass through a hole in the hot iron. He
then put a small bird into the receiver, who breathed that air without any
inconvenience, or suffering the least disorder. But the same experiment
being made with a cube of hot brass, a bird put into that air died in a few
minutes. Brass, indeed, stinks even when cold, and much more when hot;
lead, too, when hot, yields a very unwholesome steam; but iron is always
sweet and every way taken is wholesome and friendly to the human body—
except in weapons.
That warmed rooms make people tender, and apt to catch cold, is a
mistake as great as it is (among the English) general. We have seen in the
preceding pages how the common rooms are apt to give colds; but the
writer of this paper may affirm from his own experience, and that of his
family and friends who have used warm rooms for these four winters past,
that by the use of such rooms, people are rendered less liable to take cold,
and, indeed, actually hardened. If sitting warm in a room made one subject
to take cold on going out, lying warm in bed, should by a parity of reason,
produce the same effect when we rise. Yet we find we can leap out of the
warmest bed naked, in the coldest morning, without any such danger; and in
the same manner out of warm cloaths into a cold bed. The reason is, that in
these cases the pores all close at once, the cold is shut out, and the heat
within augmented, as we soon after feel by the glowing of the flesh and

skin. Thus no one was ever known to catch cold by the use of the cold bath:
and are not cold baths allowed to harden the bodies of those that use them?
Are they not therefore frequently prescribed to the tenderest constitutions?
Now every time you go out of a warm room into the cold freezing air, you
do as it were plunge into a cold bath, and the effect is in proportion the
same; for (though perhaps you may feel somewhat chilly at first) you find
in a little time your bodies hardened and strengthened, your blood is driven
round with a brisker circulation, and a comfortable steady uniform inward
warmth succeeds that equal outward warmth you first received in the room.
Farther to confirm this assertion, we instance the Swedes, the Danes, and
the Russians: these nations are said to live in rooms, compared to ours, as
hot as ovens[49]; yet where are the hardy soldiers, though bred in their
boasted cool houses, that can, like these people, bear the fatigues of a
winter campaign in so severe a climate, march whole days to the neck in
snow, and at night entrench in ice as they do?
The mentioning of those northern nations, puts me in mind of a
considerable public advantage that may arise from the general use of these
fire-places. It is observable, that though those countries have been well
inhabited for many ages, wood is still their fuel, and yet at no very great
price; which could not have been, if they had not universally used stoves,
but consumed it as we do, in great quantities, by open fires. By the help of
this saving invention our wood may grow as fast as we consume it, and our
posterity may warm themselves at a moderate rate, without, being obliged
to fetch their fuel over the Atlantic; as, if pit-coal should not be here
discovered (which is an uncertainty) they must necessarily do.
We leave it to the political arithmetician to compute how much money
will be saved to a country, by its spending two-thirds less of fuel; how much
labour saved in cutting and carriage of it; how much more land may be
cleared by cultivation; how great the profit by the additional quantity of
work done, in those trades particularly that do not exercise the body so
much, but that the workfolks are obliged to run frequently to the fire to
warm themselves: and to physicians to say, how much healthier thick-built
towns and cities will be, now half-suffocated with sulphury smoke, when so
much less of that smoke shall be made, and the air breathed by the
inhabitants be consequently so much purer. These things it will suffice just

to have mentioned; let us proceed to give some necessary directions to the
workman who is to fix or set up these fire-places.

Directions to the Bricklayer.
The chimney being first well swept and cleansed from soot, &c. lay the
bottom plate down on the hearth, in the place where the fire-place is to
stand, which may be as forward as the hearth will allow. Chalk a line from
one of its back corners round the plate to the other corner, that you may
afterwards know its place when you come to fix it; and from those corners,
two parallel lines to the back of the chimney: make marks also on each side,
that you may know where the partition is to stand, which is to prevent any
communication between the air and smoke. Then, removing the plate, make
a hollow under it and beyond it, by taking up as many of the bricks or tiles
as you can, within your chalked lines, quite to the chimney-back. Dig out
six or eight inches deep of the earth or rubbish, all the breadth and length of
your hollow; then make a passage of four inches square (if the place will
allow so much) leading from the hollow to some place communicating with
the outer air; by outer air we mean air without the room you intend to
warm. This passage may be made to enter your hollow on either side, or in
the fore part, just as you find most convenient, the circumstances of your
chimney considered. If the fire-place is to be put up in a chamber, you may
have this communication of outer air from the stair-case; or sometimes
more easily from between the chamber floor, and the ceiling of the lower
room, making only a small hole in the wall of the house entering the space
betwixt those two joists with which your air-passage in the hearth
communicates. If this air passage be so situated as that mice may enter it,
and nestle in the hollow, a little grate of wire will keep them out. This
passage being made, and, if it runs under any part of the earth, tiled over
securely, you may proceed to raise your false back. This may be of four
inches or two inches thickness, as you have room, but let it stand at least
four inches from the true chimney-back. In narrow chimneys this false back
runs from jamb to jamb, but in large old-fashioned chimneys, you need not
make it wider than the back of the fire-place. To begin it, you may form an
arch nearly flat, of three bricks end to end, over the hollow, to leave a
passage the breadth of the iron fire-place, and five or six inches deep,
rounding at bottom, for the smoke to turn and pass under the false back, and

so behind it up the chimney. The false back is to rise till it is as high as the
breast of the chimney, and then to close over to the breast[50]; always
observing, if there is a wooden mantle-tree, to close above it. If there is no
wood in the breast, you may arch over and close even with the lower part of
the breast. By this closing the chimney is made tight, that no air or smoke
can pass up it, without going under the false back. Then from side to side of
your hollow, against the marks you made with chalk, raise a tight partition,
brick-on-edge, to separate the air from the smoke, bevelling away to half an
inch the brick that comes just under the air-hole, that the air may have a free
passage up into the air-box: lastly, close the hearth over that part of the
hollow that is between the false back and the place of the bottom plate,
coming about half an inch under the plate, which piece of hollow hearth
may be supported by a bit or two of old iron-hoop; then is your chimney
fitted to receive the fire-place.
To set it, lay first a little bed of mortar all round the edges of the hollow,
and over the top of the partition: then lay down your bottom plate in its
place (with the rods in it) and tread it till it lies firm. Then put a little fine
mortar (made of loam and lime, with a little hair) into its joints, and set in
your back plate, leaning it for the present against the false back: then set in
your air-box, with a little mortar in its joints; then put in the two sides,
closing them up against the air-box, with mortar in their grooves, and fixing
at the same time your register: then bring up your back to its place, with
mortar in its grooves, and that will bind the sides together. Then put in your
front plate, placing it as far back in the groove as you can, to leave room for
the sliding plate: then lay on your top plate, with mortar in its grooves also,
screwing the whole firmly together by means of the rods. The capital letters
A B D E, &c. in Plate VIII., shew the corresponding parts of the several
plates. Lastly, the joints being pointed all round on the outside, the fire-
place is fit for use.
When you make your first fire in it, perhaps if the chimney be thoroughly
cold, it may not draw, the work too being all cold and damp. In such case,
put first a few shovels of hot coals in the fire-place, then lift up the
chimney-sweeper's trap-door, and putting in a sheet or two of flaming
paper, shut it again, which will set the chimney a drawing immediately, and
when once it is filled with a column of warm air, it will draw strongly and
continually.

The drying of the mortar and work by the first fire may smell
unpleasantly, but that will soon be over.
In some shallow chimneys, to make more room for the false back and its
flue, four inches or more of the chimney back may be picked away.
Let the room be made as tight as conveniently it may be, so will the outer
air, that must come in to supply the room and draught of the fire, be all
obliged to enter through the passage under the bottom plate, and up through
the air-box, by which means it will not come cold to your backs, but be
warmed as it comes in, and mixed with the warm air round the fire-place,
before it spreads in the room.
But as a great quantity of cold air, in extreme cold weather especially,
will presently enter a room if the door be carelessly left open, it is good to
have some contrivance to shut it, either by means of screw hinges, a spring,
or a pulley.
When the pointing in the joints is all dry and hard, get some powder of
black lead (broken bits of black lead crucibles from the silver-smiths,
pounded fine, will do) and mixing it with a little rum and water, lay it on,
when the plates are warm, with a hard brush, over the top and front-plates,
part of the side and bottom-plates, and over all the pointing; and, as it dries,
rub it to a gloss with the same brush, so the joints will not be discerned, but
it will look all of a piece, and shine like new iron. And the false back being
plaistered and white-washed, and the hearth reddened, the whole will make
a pretty appearance. Before the black lead is laid on, it would not be amiss
to wash the plates with strong lee and a brush, or soap and water, to cleanse
them from any spots of grease or filth that may be on them. If any grease
should afterwards come on them, a little wet ashes will get it out.
If it be well set up, and in a tolerable good chimney, smoke will draw in
from as far as the fore part of the bottom plate, as you may try by a bit of
burning paper.
People are at first apt to make their rooms too warm, not imagining how
little a fire will be sufficient. When the plates are no hotter than that one
may just bear the hand on them, the room will generally be as warm as you
desire it.

Soon after the foregoing piece was published, some persons in England,
in imitation of Mr. Franklin's invention, made what they call Pensylvanian
Fire-places, with improvements; the principal of which pretended
improvements is, a contraction of the passages in the air-box, originally
designed for admitting a quantity of fresh air, and warming it as it entered
the room. The contracting these passages gains indeed more room for the
grate, but in a great measure defeats their intention. For if the passages in
the air-box do not greatly exceed in dimensions the amount of all the
crevices by which cold air can enter the room, they will not considerably
prevent, as they were intended to do, the entry of cold air through these
crevices.

FOOTNOTES:

[44] Body or matter of any sort, is said to be specifically heavier or lighter than
other matter, when it has more or less substance or weight in the same
dimensions.
[45] As the writer is neither physician nor philosopher, the reader may expect he
should justify these his opinions by the authority of some that are so. M. Clare,
F. R. S. in his treatise of The Motion of Fluids, says, page 246, &c. "And here it
may be remarked, that it is more prejudicial to health to sit near a window or
door, in a room where there are many candles and a fire, than in a room without;
for the consumption of air thereby occasioned, will always be very considerable,
and this must necessarily be replaced by cold air from without. Down the
chimney can enter none, the stream of warm air always arising therein absolutely
forbids it, the supply must therefore come in wherever other openings shall be
found. If these happen to be small, let those who sit near them beware; the
smaller the floodgate, the smarter will be the stream. Was a man, even in a
sweat, to leap into a cold bath, or jump from his warm bed, in the intensest cold,
even in a frost, provided he do not continue over-long therein, and be in health
when he does this, we see by experience that he gets no harm. If he sits a little
while against a window, into which a successive current of cold air comes, his
pores are closed, and he gets a fever. In the first case, the shock the body
endures, is general, uniform, and therefore less fierce; in the other, a single part,
a neck, or ear perchance, is attacked, and that with the greater violence probably,
as it is done by a successive stream of cold air. And the cannon of a battery,
pointed against a single part of a bastion, will easier make a breach than were
they directed to play singly upon the whole face, and will admit the enemy much
sooner into the town."

That warm rooms, and keeping the body warm in winter, are means of
preventing such diseases, take the opinion of that learned Italian physician
Antonino Parcio, in the preface to his tract de Militis Sanitate tuenda, where,
speaking of a particular wet and cold winter, remarkable at Venice for its
sickliness, he says, "Popularis autem pleuritis quæ Venetiis sæviit mensibus Dec.
Jan. Feb. ex cæli, aërisque inclementia facta est, quod non habeant hypocausta
[stove-rooms] & quod non soliciti sunt Itali omnes de auribus, temporibus, collo,
totoque corpore defendendis ab injuriis aëris; et tegmina domorum Veneti
disponant parum inclinata, ut nives diutius permaneant super tegmina. E contra,
Germani, qui experiuntur cæli inclementiam, perdidicere sese defendere ab aëris
injuria. Tecta construunt multum inclinata, ut decidant nives. Germani abundant
lignis, domusque hypocaustis; foris autem incedunt pannis pellibus, gossipio,
bene mehercule loricati atque muniti. In Bavaria interrogabam (curiositate motus
videndi Germaniam) quot nam elapsis mensibus pleuritide vel peripneumonia
fuissent absumti: dicebant vix unus aut alter illis temporibus pleuritide fuit
correptus."
The great Dr. Boerhaave, whose authority alone might be sufficient, in his
Aphorisms, mentions, as one antecedent cause of pleurisies, "A cold air, driven
violently through some narrow passage upon the body, overheated by labour or
fire."
The eastern physicians agree with the Europeans in this point; witness the
Chinese treatise entitled, Tschang seng; i.e. The Art of procuring Health and
long Life, as translated in Pere Du Halde's account of China, which has this
passage. "As, of all the passions which ruffle us, anger does the most mischief,
so of all the malignant affections of the air, a wind that comes through any
narrow passage, which is cold and piercing, is most dangerous; and coming upon
us unawares insinuates itself into the body, often causing grievous diseases. It
should therefore be avoided, according to the advice of the ancient proverb, as
carefully as the point of an arrow." These mischiefs are avoided by the use of the
new-invented fire-places, as will be shown hereafter.
[46] The shutter is slid up and down in this manner, only in those fire-places
which are so made as that the distance between the top of the arched opening,
and the bottom plate, is the same as the distance between it and the top plate.
Where the arch is higher, as it is in the draught annexed (which is agreeable to
the last improvements) the shutter is set by, and applied occasionally; because if
it were made deep enough to close the whole opening when slid down, it would
hide part of it when up.
[47] My Lord Molesworth, in his account of Denmark, says, "That few or none
of the people there are troubled with coughs, catarrhs, consumptions, or such
like diseases of the lungs; so that in the midst of winter in the churches, which
are very much frequented, there is no noise to interrupt the attention due to the
preacher. I am persuaded (says he) their warm stoves contribute to their freedom
from these kind of maladies." page 91.
[48] People who have used these fire-places, differ much in their accounts of the
wood saved by them. Some say five-sixths, others three-fourths, and others
much less. This is owing to the great difference there was in their former fires;
some (according to the different circumstances of their rooms and chimneys)
having been used to make very large, others middling, and others, of a more

sparing temper, very small ones: while in these fire-places (their size and
draught being nearly the same), the consumption is more equal. I suppose, taking
a number of families together, that two-thirds, or half the wood, at least, is
saved. My common room, I know, is made thrice as warm as it used to be, with a
quarter of the wood I formerly consumed there.
[49] Mr. Boyle, in his experiments and observations upon cold, Shaw's
Abridgement, Vol. I. p. 684, says, "It is remarkable, that while the cold has
strange and tragical effects at Moscow, and elsewhere, the Russians and
Livonians should be exempt from them, who accustom themselves to pass
immediately from a great degree of heat, to as great an one of cold, without
receiving any visible prejudice thereby. I remember being told by a person of
unquestionable credit, that it was a common practice among them, to go from a
hot stove, into cold water; the same was also affirmed to me by another who
resided at Moscow. This tradition is likewise abundantly confirmed by
Olearius."—"It is a surprising thing, says he, to see how far the Russians can
endure heat; and how, when it makes them ready to faint, they can go out of their
stoves, stark naked, both men and women, and throw themselves into cold water;
and even in winter wallow in the snow."
[50] See page 240, where the trap-door is described that ought to be in this
closing.

T O D R . I N G E N H A U S Z , P H Y S I C I A N T O T H E E M P E R O R , AT
VIENNA[51].

On the Causes and Cure of Smoky Chimnies.

At Sea, Aug., 28, 1785.
DEAR FRIEND,

In one of your letters, a little before I left France, you desire me to give
you in writing my thoughts upon the construction and use of chimneys, a
subject you had sometimes heard me touch upon in conversation. I embrace
willingly this leisure afforded by my present situation to comply with your
request, as it will not only show my regard to the desires of a friend, but
may at the same time be of some utility to others; the doctrine of chimneys
appearing not to be as yet generally well understood, and mistakes
respecting them being attended with constant inconvenience, if not
remedied, and with fruitless expence, if the true remedies are mistaken.
Those who would be acquainted with this subject should begin by
considering on what principle smoke ascends in any chimney. At first many

are apt to think that smoke is in its nature and of itself specifically lighter
than air, and rises in it for the same reason that cork rises in water. These
see no case why smoke should not rise in the chimney, though the room be
ever so close. Others think there is a power in chimneys to draw up the
smoke, and that there are different forms of chimneys which afford more or
less of this power. These amuse themselves with searching for the best
form. The equal dimensions of a funnel in its whole length is not thought
artificial enough, and it is made, for fancied reasons, sometimes tapering
and narrowing from below upwards, and sometimes the contrary, &c. &c. A
simple experiment or two may serve to give more correct ideas. Having lit a
pipe of tobacco, plunge the stem to the bottom of a decanter half filled with
cold water; then putting a rag over the bowl, blow through it and make the
smoke descend in the stem of the pipe, from the end of which it will rise in
bubbles through the water; and being thus cooled, will not afterwards rise to
go out through the neck of the decanter, but remain spreading itself and
resting on the surface of the water. This shows that smoke is really heavier
than air, and that it is carried upwards only when attached to, or acted upon,
by air that is heated, and thereby rarefied and rendered specifically lighter
than the air in its neighbourhood.
Smoke being rarely seen but in company with heated air, and its upward
motion being visible, though that of the rarefied air that drives it is not so,
has naturally given rise to the error.
I need not explain to you, my learned friend, what is meant by rarefied
air; but if you make the public use you propose of this letter, it may fall into
the hands of some who are unacquainted with the term and with the thing.
These then may be told, that air is a fluid which has weight as well as
others, though about eight hundred times lighter than water. That heat
makes the particles of air recede from each other and take up more space, so
that the same weight of air heated will have more bulk, than equal weights
of cold air which may surround it, and in that case must rise, being forced
upwards by such colder and heavier air, which presses to get under it and
take its place. That air is so rarefied or expanded by heat may be proved to
their comprehension, by a lank blown bladder, which, laid before a fire, will
soon swell, grow tight and burst.

Plate IX. Vol. II. page 269.

View larger image here
Published as the Act directs, April 1, 1806, by Longman, Hurst, Rees & Orme, Paternoster Row.

Another experiment may be to take a glass tube about an inch in
diameter, and twelve inches long, open at both ends and fixed upright on
legs, so that it need not be handled, for the hands might warm it. At the end
of a quill fasten five or six inches of the finest light filament of silk, so that
it may be held either above the upper end of the tube or under the lower
end, your warm hand being at a distance by the length of the quill. (Plate
IX. fig. 1.) If there were any motion of air through the tube, it would
manifest itself by its effect on the silk; but if the tube and the air in it are of
the same temperature with the surrounding air, there will be no such
motion, whatever may be the form of the tube, whether crooked or strait,
narrow below and widening upwards, or the contrary; the air in it will be

quiescent. Warm the tube, and you will find, as long as it continues warm, a
constant current of air entering below and passing up through it, till
discharged at the top; because the warmth of the tube being communicated
to the air it contains rarefies that air and makes it lighter than the air
without, which therefore presses in below, forces it upwards, and follows
and takes its place, and is rarefied in its turn. And, without warming the
tube, if you hold under it a knob of hot iron, the air thereby heated will rise
and fill the tube, going out at its top, and this motion in the tube will
continue as long as the knob remains hot, because the air entering the tube
below is heated and rarefied by passing near and over that knob.
That this motion is produced merely by the difference of specific gravity
between the fluid within and that without the tube, and not by any fancied
form of the tube itself, may appear by plunging it into water contained in a
glass jar a foot deep, through which such motion might be seen. The water
within and without the tube being of the same specific gravity, balance each
other, and both remain at rest. But take out the tube, stop its bottom with a
finger and fill it with olive oil, which is lighter than water, then stopping the
top, place it as before, its lower end under water, its top a very little above.
As long as you keep the bottom stopt, the fluids remain at rest, but the
moment it is unstopt, the heavier enters below, forces up the lighter, and
takes its place. And the motion then ceases, merely because the new fluid
cannot be successively made lighter, as air may be by a warm tube.
In fact, no form of the funnel of a chimney has any share in its operation
or effect respecting smoke, except its height. The longer the funnel, if erect,
the greater its force when filled with heated and rarefied air, to draw in
below and drive up the smoke, if one may, in compliance with custom, use
the expression draw, when in fact it is the superior weight of the
surrounding atmosphere that presses to enter the funnel below, and so
drives up before it the smoke and warm air it meets with in its passage.
I have been the more particular in explaining these first principles,
because, for want of clear ideas respecting them, much fruitless expence has
been occasioned; not only single chimneys, but in some instances, within
my knowledge, whole stacks having been pulled down and rebuilt with
funnels of different forms, imagined more powerful in drawing smoke; but
having still the same height and the same opening below, have performed
no better than their predecessors.

What is it then which makes a smoky chimney, that is, a chimney which,
instead of conveying up all the smoke, discharges a part of it into the room,
offending the eyes and damaging the furniture?
The causes of this effect, which have fallen under my observation,
amount to nine, differing from each other, and therefore requiring different
remedies.
1. Smoky chimneys in a new house, are such, frequently from mere want
of air. The workmanship of the rooms being all good, and just out of the
workman's hand, the joints of the boards of the flooring, and of the pannels
of wainscotting are all true and tight, the more so as the walls, perhaps not
yet thoroughly dry, preserve a dampness in the air of the room which keeps
the wood-work swelled and close. The doors and the sashes too, being
worked with truth, shut with exactness, so that the room is as tight as a
snuff-box, no passage being left open for air to enter, except the key-hole,
and even that is sometimes covered by a little dropping shutter. Now if
smoke cannot rise but as connected with rarefied air, and a column of such
air, suppose it filling the funnel, cannot rise, unless other air be admitted to
supply its place; and if, therefore, no current of air enter the opening of the
chimney, there is nothing to prevent the smoke coming out into the room. If
the motion upwards of the air in a chimney that is freely supplied, be
observed by the rising of the smoke or a feather in it, and it be considered
that in the time such feather takes in rising from the fire to the top of the
chimney, a column of air equal to the content of the funnel must be
discharged, and an equal quantity supplied from the room below, it will
appear absolutely impossible that this operation should go on if the tight
room is kept shut; for were there any force capable of drawing constantly so
much air out of it, it must soon be exhausted like the receiver of an air-
pump, and no animal could live in it. Those therefore who stop every
crevice in a room to prevent the admission of fresh air, and yet would have
their chimney carry up the smoke, require inconsistencies, and expect
impossibilities. Yet under this situation, I have seen the owner of a new
house, in despair, and ready to sell it for much less than it cost, conceiving
it uninhabitable, because not a chimney in any one of its rooms would carry
off the smoke, unless a door or window were left open. Much expence has
also been made, to alter and amend new chimneys which had really no
fault; in one house particularly that I knew, of a nobleman in Westminster,

that expence amounted to no less than three hundred pounds, after his house
had been, as he thought, finished and all charges paid. And after all, several
of the alterations were ineffectual, for want of understanding the true
principles.
Remedies. When you find on trial, that opening the door or a window,
enables the chimney to carry up all the smoke, you may be sure that want of
air from without, was the cause of its smoking. I say from without, to guard
you against a common mistake of those who may tell you, the room is large,
contains abundance of air, sufficient to supply any chimney, and therefore it
cannot be that the chimney wants air. These reasoners are ignorant, that the
largeness of a room, if tight, is in this case of small importance, since it
cannot part with a chimney full of its air without occasioning so much
vacuum; which it requires a great force to effect, and could not be borne if
effected.
It appearing plainly, then, that some of the outward air must be admitted,
the question will be, how much is absolutely necessary; for you would
avoid admitting more, as being contrary to one of your intentions in having
a fire, viz. that of warming your room. To discover this quantity, shut the
door gradually while a middling fire is burning, till you find that, before it
is quite shut, the smoke begins to come out into the room, then open it a
little till you perceive the smoke comes out no longer. There hold the door,
and observe the width of the open crevice between the edge of the door and
the rabbit it should shut into. Suppose the distance to be half an inch, and
the door eight feet high, you find thence that your room requires an
entrance for air equal in area to ninety-six half inches, or forty-eight square
inches, or a passage of six inches by eight. This however is a large
supposition, there being few chimneys, that, having a moderate opening and
a tolerable height of funnel, will not be satisfied with such a crevice of a
quarter of an inch; and I have found a square of six by six, or thirty-six
square inches, to be a pretty good medium, that will serve for most
chimneys. High funnels, with small and low openings, may indeed be
supplied thro' a less space, because, for reasons that will appear hereafter,
the force of levity, if one may so speak, being greater in such funnels, the
cool air enters the room with greater velocity, and consequently more enters
in the same time. This however has its limits; for experience shows, that no
increased velocity, so occasioned, has made the admission of air through the

key-hole equal in quantity to that through an open door; though through the
door the current moves slowly, and through the key-hole with great rapidity.
It remains then to be considered how and where this necessary quantity
of air from without is to be admitted so as to be least inconvenient. For if at
the door, left so much open, the air thence proceeds directly to the chimney,
and in its way comes cold to your back and heels as you sit before your fire.
If you keep the door shut, and raise a little the sash of your window, you
feel the same inconvenience. Various have been the contrivances to avoid
this, such as bringing in fresh air through pipes in the jams of the chimney,
which, pointing upwards, should blow the smoke up the funnel; opening
passages into the funnel above, to let in air for the same purpose. But these
produce an effect contrary to that intended: for as it is the constant current
of air passing from the room through the opening of the chimney into the
funnel which prevents the smoke coming out into the room, if you supply
the funnel by other means or in other ways with the air it wants, and
especially if that air be cold, you diminish the force of that current, and the
smoke in its effort to enter the room finds less resistance.
The wanted air must then indispensably be admitted into the room, to
supply what goes off through the opening of the chimney. M. Gauger, a
very ingenious and intelligent French writer on the subject, proposes with
judgment to admit it above the opening of the chimney; and to prevent
inconvenience from its coldness, he directs its being made to pass in its
entrance through winding cavities made behind the iron back and sides of
the fire-place, and under the iron hearth-plate; in which cavities it will be
warmed, and even heated, so as to contribute much, instead of cooling, to
the warming of the room. This invention is excellent in itself, and may be
used with advantage in building new houses; because the chimneys may
then be so disposed, as to admit conveniently the cold air to enter such
passages: but in houses built without such views, the chimneys are often so
situated, as not to afford that convenience, without great and expensive
alterations. Easy and cheap methods, though not quite so perfect in
themselves, are of more general utility; and such are the following.
In all rooms where there is a fire, the body of air warmed and rarefied
before the chimney is continually changing place, and making room for
other air that is to be warmed in its turn. Part of it enters and goes up the
chimney, and the rest rises and takes place near the ceiling. If the room be

lofty, that warm air remains above our heads as long as it continues warm,
and we are little benefited by it, because it does not descend till it is cooler.
Few can imagine the difference of climate between the upper and lower
parts of such a room, who have not tried it by the thermometer, or by going
up a ladder till their heads are near the ceiling. It is then among this warm
air that the wanted quantity of outward air is best admitted, with which
being mixed, its coldness is abated, and its inconvenience diminished so as
to become scarce observable. This may be easily done, by drawing down
about an inch the upper sash of a window; or, if not moveable, by cutting
such a crevice through its frame; in both which cases, it will be well to
place a thin shelf of the length, to conceal the opening, and sloping upwards
to direct the entering air horizontally along and under the ceiling. In some
houses the air may be admitted by such a crevice made in the wainscot,
cornish or plastering, near the ceiling and over the opening of the chimney.
This, if practicable, is to be chosen, because the entering cold air will there
meet with the warmest rising air from before the fire, and be soonest
tempered by the mixture. The same kind of shelf should also be placed here.
Another way, and not a very difficult one, is to take out an upper pane of
glass in one of your sashes, set in a tin frame, (Plate, Fig. 2.) giving it two
springing angular sides, and then replacing it, with hinges below on which
it may be turned to open more or less above. It will then have the
appearance of an internal sky light. By drawing this pane in, more or less,
you may admit what air you find necessary. Its position will naturally throw
that air up and along the ceiling. This is what is called in France a Was ist
das? As this is a German question, the invention is probably of that nation,
and takes its name from the frequent asking of that question when it first
appeared. In England, some have of late years cut a round hole about five
inches diameter in a pane of the sash and placed against it a circular plate of
tin hung on an axis, and cut into vanes, which, being separately bent a little
obliquely, are acted upon by the entering air, so as to force the plate
continually round like the vanes of a windmill. This admits the outward air,
and by the continual whirling of the vanes, does in some degree disperse it.
The noise only, is a little inconvenient.
2. A second cause of the smoking of chimneys is, their openings in the
room being too large; that is, too wide, too high, or both. Architects in
general have no other ideas of proportion in the opening of a chimney, than
what relate to symmetry and beauty, respecting the dimensions of the room;

[52]
while its true proportion, respecting its function and utility depends on
quite other principles; and they might as properly proportion the step in a
stair-case to the height of the story, instead of the natural elevation of men's
legs in mounting. The proportion then to be regarded, is what relates to the
height of the funnel. For as the funnels in the different stories of a house are
necessarily of different heights or lengths, that from the lowest floor being
the highest or longest, and those of the other floors shorter and shorter, till
we come to those in the garrets, which are of course the shortest; and the
force of draft being, as already said, in proportion to the height of funnel
filled with rarefied air; and a current of air from the room into the chimney,
sufficient to fill the opening, being necessary to oppose and prevent the
smoke coming out into the room; it follows, that the openings of the longest
funnels may be larger, and that those of the shorter funnels should be
smaller. For if there be a large opening to a chimney that does not draw
strongly, the funnel may happen to be furnished with the air it demands by a
partial current entering on one side of the opening, and, leaving the other
side free of any opposing current, may permit the smoke to issue there into
the room. Much too of the force of draft in a funnel depends on the degree
of rarefaction in the air it contains, and that depends on the nearness to the
fire of its passage in entering the funnel. If it can enter far from the fire on
each side, or far above the fire in a wide or high opening, it receives little
heat in passing by the fire, and the contents of the funnel is by that means
less different in levity from the surrounding atmosphere, and its force in
drawing consequently weaker. Hence if too large an opening be given to
chimneys in upper rooms, those rooms will be smoky: on the other hand, if
too small openings be given to chimneys in the lower rooms, the entering
air, operating too directly and violently on the fire, and afterwards
strengthening the draft as it ascends the funnel, will consume the fuel too
rapidly.
Remedy. As different circumstances frequently mix themselves in these
matters, it is difficult to give precise dimensions for the openings of all
chimneys. Our fathers made them generally much too large; we have
lessened them; but they are often still of greater dimension than they should
be, the human eye not being easily reconciled to sudden and great changes.
If you suspect that your chimney smokes from the too great dimension of its
opening, contract it by placing moveable boards so as to lower and narrow
it gradually, till you find the smoke no longer issues into the room. The

proportion so found will be that which is proper for that chimney, and you
may employ the bricklayer or mason to reduce it accordingly. However, as,
in building new houses, something must be sometimes hazarded, I would
make the openings in my lower rooms about thirty inches square and
eighteen deep, and those in the upper, only eighteen inches square and not
quite so deep; the intermediate ones diminishing in proportion as the height
of funnel diminished. In the larger openings, billets of two feet long, or half
the common length of cordwood, may be burnt conveniently; and for the
smaller, such wood may be sawed into thirds. Where coals are the fuel, the
grates will be proportioned to the openings. The same depth is nearly
necessary to all, the funnels being all made of a size proper to admit a
chimney-sweeper. If in large and elegant rooms custom or fancy should
require the appearance of a larger chimney, it may be formed of expensive
marginal decorations, in marble, &c. In time perhaps, that which is fittest in
the nature of things may come to be thought handsomest. But at present,
when men and women in different countries show themselves dissatisfied
with the forms God has given to their heads, waists and feet, and pretend to
shape them more perfectly, it is hardly to be expected that they will be
content always with the best form of a chimney. And there are some, I
know, so bigotted to the fancy of a large noble opening, that rather than
change it, they would submit to have damaged furniture, sore eyes, and
skins almost smoked to bacon.
3. Another cause of smoky chimneys is, too short a funnel. This happens
necessarily in some cases, as where a chimney is required in a low building;
for, if the funnel be raised high above the roof, in order to strengthen its
draft, it is then in danger of being blown down, and crushing the roof in its
fall.
Remedies. Contract the opening of the chimney, so as to oblige all the
entering air to pass through or very near the fire; whereby it will be more
heated and rarefied, the funnel itself be more warmed, and its contents have
more of what may be called the force of levity, so as to rise strongly and
maintain a good draft at the opening.
Or you may in some cases, to advantage, build additional stories over the
low building, which will support a high funnel.

If the low building be used as a kitchen, and a contraction of the opening
therefore inconvenient, a large one being necessary, at least when there are
great dinners, for the free management of so many cooking utensils; in such
case, I would advise the building of two more funnels joining to the first,
and having three moderate openings, one to each funnel, instead of one
large one. When there is occasion to use but one, the other two may be kept
shut by sliding plates, hereafter to be described;[53] and two or all of them
may be used together when wanted. This will indeed be an expence, but not
an useless one, since your cooks will work with more comfort, see better
than in a smoky kitchen what they are about, your victuals will be cleaner
dressed, and not taste of smoke, as is often the case; and to render the effect
more certain, a stack of three funnels may be safely built higher above the
roof than a single funnel.
The case of too short a funnel is more general than would be imagined,
and often found where one would not expect it. For it is not uncommon, in
ill-contrived buildings, instead of having a funnel for each room or fire-
place, to bend and turn the funnel of an upper room so as to make it enter
the side of another funnel that comes from below. By this means the upper
room funnel is made short of course, since its length can only be reckoned
from the place where it enters the lower room funnel; and that funnel is also
shortened by all the distance between the entrance of the second funnel and
the top of the stack: for all that part being readily supplied with air through
the second funnel, adds no strength to the draught, especially as that air is
cold when there is no fire in the second chimney. The only easy remedy
here is, to keep the opening shut of that funnel in which there is no fire.
4. Another very common cause of the smoking of
chimneys, is, their overpowering one another. For instance, if there be
two chimneys in one large room, and you make fires in both of them, the
doors and windows close shut, you will find that the greater and stronger
fire shall overpower the weaker, and draw air down its funnel to supply its
own demand; which air descending in the weaker funnel will drive down its
smoke, and force it into the room. If, instead of being in one room, the two
chimneys are in two different rooms, communicating by a door, the case is
the same whenever that door is open. In a very tight house, I have known a
kitchen chimney on the lowest floor, when it had a great fire in, it,

overpower any other chimney in the house, and draw air and smoke into its
room, as often as the door was opened communicating with the stair-case.
Remedy. Take care that every room has the means of supplying itself
from without, with the air its chimney may require, so that no one of them
may be obliged to borrow from another, nor under the necessity of lending.
A variety of these means have been already described.
5. Another cause of smoking is, when the tops of chimneys are
commanded by higher buildings, or by a hill, so that the wind blowing over
such eminences falls like water over a dam, sometimes almost
perpendicularly on the tops of the chimneys that lie in its way, and beats
down the smoke contained in them.
Remedy. That commonly applied to this case, is a turncap made of tin or
plate iron, covering the chimney above and on three sides, open on one
side, turning on a spindle, and which, being guided or governed by a vane,
always presents its back to the current. This I believe may be generally
effectual, though not certain, as there may be cases in which it will not
succeed. Raising your funnels, if practicable, so as their tops may be higher,
or at least equal with the commanding eminence, is more to be depended
on. But the turning cap, being easier and cheaper, should first be tried. If
obliged to build in such a situation, I would chuse to place my doors on the
side next the hill, and the backs of my chimneys on the furthest side; for
then the column of air falling over the eminence, and of course pressing on
that below and forcing it to enter the doors or Was ist dases on that side,
would tend to balance the pressure down the chimneys, and leave the
funnels more free in the exercise of their functions.
6. There is another case of command, the reverse of that last mentioned.
It is where the commanding eminence is farther from the wind than the
chimney commanded. To explain this a figure may be necessary. Suppose
then a building whose side A happens to be exposed to the wind, and forms
a kind of dam against its progress. (Plate, Figure 3.) The air obstructed by
this dam will, like water, press and search for passages through it; and
finding the top of the chimney B, below the top of the dam, it will force
itself down that funnel, in order to get through by some door or window
open on the other side of the building. And if there be a fire in such
chimney, its smoke is of course beat down, and fills the room.

Remedy. I know of but one, which is to raise such funnel higher than the
roof, supporting it, if necessary by iron bars. For a turn-cap in this case has
no effect, the dammed up air pressing down through it in whatever position
the wind may have placed its opening.
I know a city in which many houses are rendered smoky by this
operation. For their kitchens being built behind, and connected by a passage
with the houses, and the tops of the kitchen chimneys lower than the top of
the houses, the whole side of a street, when the wind blows against its back,
forms such a dam, as above described; and the wind, so obstructed, forces
down those kitchen chimneys (especially when they have but weak fires in
them) to pass through the passage and house into the street. Kitchen
chimneys, so formed and situated, have another inconvenience. In summer,
if you open your upper room windows for air, a light breeze blowing over
your kitchen chimney towards the house, though not strong enough to force
down its smoke as aforesaid, is sufficient to waft it into your windows, and
fill the rooms with it; which, besides the disagreeableness, damages your
furniture.
7. Chimneys, otherwise drawing well, are sometimes made to smoke by
the improper and inconvenient situation of a door. When the door and
chimney are on the same side of the room as in the figure, if the door A,
being in the corner, is made to open against the wall (Plate, Figure 4) which
is common, as being there, when open, more out of the way, it follows, that
when the door is only opened in part, a current of air rushing in passes
along the wall into and across the opening of the chimney B, and flirts some
of the smoke out into the room. This happens more certainly when the door
is shutting, for then the force of the current is augmented, and becomes very
inconvenient to those who, warming themselves by the fire, happen to sit in
its way.
The remedies are obvious and easy. Either put an intervening skreen from
the wall round great part of the fire-place; or, which is perhaps preferable,
shift the hinges of your door, so as it may open the other way, and when
open throw the air along the other wall.
8. A room, that has no fire in its chimney, is sometimes filled with smoke
which is received at the top of its funnel and descends into the room. In a
former paper[54] I have already explained the descending currents of air in

cold funnels; it may not be amiss however to repeat here, that funnels
without fires have an effect, according to their degree of coldness or
warmth, on the air that happens to be contained in them. The surrounding
atmosphere is frequently changing its temperature; but stacks of funnels,
covered from winds and sun by the house that contains them, retain a more
equal temperature. If, after a warm season, the outward air suddenly grows
cold, the empty warm funnels begin to draw strongly upward; that is, they
rarefy the air contained in them, which of course rises, cooler air enters
below to supply its place, is rarefied in its turn and rises; and this operation
continues till the funnel grows cooler, or the outward air warmer, or both,
when the motion ceases. On the other hand, if after a cold season, the
outward air suddenly grows warm and of course lighter, the air contained in
the cool funnels, being heavier, descends into the room; and the warmer air
which enters their tops being cooled in its turn, and made heavier, continues
to descend; and this operation goes on, till the funnels are warmed by the
passing of warm air through them, or the air itself grows cooler. When the
temperature of the air and of the funnels is nearly equal, the difference of
warmth in the air between day and night is sufficient to produce these
currents, the air will begin to ascend the funnels as the cool of the evening
comes on, and this current will continue till perhaps nine or ten o'clock the
next morning, when it begins to hesitate; and as the heat of the day
approaches, it sets downwards, and continues so till towards evening, when
it again hesitates for some time, and then goes upwards constantly during
the night, as before mentioned. Now when smoke issuing from the tops of
neighbouring funnels passes over the tops of funnels which are at the time
drawing downwards, as they often are in the middle part of the day, such
smoke is of necessity drawn into these funnels, and descends with the air
into the chamber.
The remedy is to have a sliding plate, hereafter described[55], that will
shut perfectly the offending funnel.
9. Chimneys which generally draw well, do nevertheless sometimes give
smoke into the rooms, it being driven down by strong winds passing over
the tops of their funnels, though not descending from any commanding
eminence. This case is most frequent where the funnel is short, and the
opening turned from the wind. It is the more grievous, when it happens to
be a cold wind that produces the effect, because when you most want your

fire, you are sometimes obliged to extinguish it. To understand this, it may
be considered that the rising light air, to obtain a free issue from the funnel,
must push out of its way or oblige the air that is over it to rise. In a time of
calm or of little wind this is done visibly, for we see the smoke that is
brought up by that air rise in a column above the chimney. But when a
violent current of air, that is, a strong wind, passes over the top of a
chimney, its particles have received so much force, which keeps them in a
horizontal direction and follow each other so rapidly, that the rising light air
has not strength sufficient to oblige them to quit that direction and move
upwards to permit its issue. Add to this, that some of the current passing
over that side of the funnel which it first meets with, viz. at A, (Plate IX.
Figure 5.) having been compressed by the resistance of the funnel, may
expand itself over the flue, and strike the interior opposite side at B, from
whence it may be reflected downwards and from side to side in the
direction of the pricked lines c c c.
Remedies. In some places, particularly in Venice, where they have not
stacks of chimneys but single flues, the custom is, to open or widen the top
of the flue rounding in the true form of a funnel; (Plate, Figure 6) which
some think may prevent the effect just mentioned, for that the wind blowing
over one of the edges into the funnel may be slanted out again on the other
side by its form. I have had no experience of this; but I have lived in a
windy country, where the contrary is practised, the tops of the flues being
narrowed inwards, so as to form a slit for the issue of the smoke, long as the
breadth of the funnel, and only four inches wide. This seems to have been
contrived on a supposition, that the entry of the wind would thereby be
obstructed, and perhaps it might have been imagined, that the whole force
of the rising warm air being condensed, as it were, in the narrow opening,
would thereby be strengthened, so as to overcome the resistance of the
wind. This however did not always succeed; for when the wind was at
north-east and blew fresh, the smoke was forced down by fits into the room
I commonly sat in, so as to oblige me to shift the fire into another. The
position of the slit of this funnel was indeed north-east and south-west.
Perhaps if it had lain across the wind, the effect might have been different.
But on this I can give no certainty. It seems a matter proper to be referred to
experiment. Possibly a turn-cap might have been serviceable, but it was not
tried.

Chimneys have not been long in use in England. I formerly saw a book
printed in the time of queen Elizabeth, which remarked the then modern
improvements of living, and mentioned among others the convenience of
chimneys. "Our forefathers," said the author, "had no chimneys. There was
in each dwelling house only one place for a fire, and the smoke went out
through a hole in the roof; but now there is scarce a gentleman's house in
England that has not at least one chimney in it."—When there was but one
chimney, its top might then be opened as a funnel, and perhaps, borrowing
the form from the Venetians, it was then the flue of a chimney got that
name. Such is now the growth of luxury, that in both England and France
we must have a chimney for every room, and in some houses every
possessor of a chamber, and almost every servant, will have a fire; so that
the flues being necessarily built in stacks, the opening of each as a funnel is
impracticable. This change of manners soon consumed the firewood of
England, and will soon render fuel extremely scarce and dear in France, if
the use of coals be not introduced in the latter kingdom as it has been in the
former, where it at first met with opposition; for there is extant in the
records of one of queen Elizabeth's parliaments, a motion made by a
member, reciting, "That many dyers, brewers, smiths, and other artificers of
London, had of late taken to the use of pit-coal for their fires, instead of
wood, which filled the air with noxious vapours and smoke, very prejudicial
to the health, particularly of persons coming out of the country; and
therefore moving that a law might pass to prohibit the use of such fuel (at
least during the session of parliament) by those artificers."—It seems it was
not then commonly used in private houses. Its supposed unwholesomeness
was an objection. Luckily the inhabitants of London have got over that
objection, and now think it rather contributes to render their air salubrious,
as they have had no general pestilential disorder since the general use of
coals, when, before it, such were frequent. Paris still burns wood at an
enormous expence continually augmenting, the inhabitants having still that
prejudice to overcome. In Germany you are happy in the use of stoves,
which save fuel wonderfully: your people are very ingenious in the
management of fire; but they may still learn something in that art from the
Chinese[56], whose country being greatly populous and fully cultivated, has
little room left for the growth of wood, and having not much other fuel that
is good, have been forced upon many inventions during a course of ages,
for making a little fire go as far as possible.

I have thus gone through all the common causes of the smoking of
chimneys that I can at present recollect as having fallen under my
observation; communicating the remedies that I have known successfully
used for the different cases, together with the principles on which both the
disease and the remedy depend, and confessing my ignorance wherever I
have been sensible of it. You will do well, if you publish, as you propose,
this letter, to add in notes, or as you please, such observations as may have
occurred to your attentive mind; and if other philosophers will do the same,
this part of science, though humble, yet of great utility, may in time be
perfected. For many years past, I have rarely met with a case of a smoky
chimney, which has not been solvable on these principles, and cured by
these remedies, where people have been willing to apply them; which is
indeed not always the case; for many have prejudices in favour of the
nostrums of pretending chimney-doctors and fumists, and some have
conceits and fancies of their own, which they rather chuse to try, than to
lengthen a funnel, alter the size of an opening, or admit air into a room,
however necessary; for some are as much afraid of fresh air as persons in
the hydrophobia are of fresh water. I myself had formerly this prejudice,
this aerophobia, as I now account it, and dreading the supposed dangerous
effects of cool air, I considered it as an enemy, and closed with extreme care
every crevice in the rooms I inhabited. Experience has convinced me of my
error. I now look upon fresh air as a friend: I even sleep with an open
window. I am persuaded that no common air from without, is so
unwholesome as the air within a close room that has been often breathed
and not changed. Moist air too, which formerly I thought pernicious, gives
me now no apprehensions: for considering that no dampness of air applied
to the outside of my skin can be equal to what is applied to and touches it
within, my whole body being full of moisture, and finding that I can lie two
hours in a bath twice a week, covered with water, which certainly is much
damper than any air can be, and this for years together, without catching
cold, or being in any other manner disordered by it, I no longer dread mere
moisture, either in air or in sheets or shirts: and I find it of importance to the
happiness of life, the being freed from vain terrors, especially of objects
that we are every day exposed inevitably to meet with. You physicians have
of late happily discovered, after a contrary opinion had prevailed some
ages, that fresh and cool air does good to persons in the small pox and other
fevers. It is to be hoped, that in another century or two we may all find out,

that it is not bad even for people in health. And as to moist air, here I am at
this present writing in a ship with above forty persons, who have had no
other but moist air to breathe for six weeks past; every thing we touch is
damp, and nothing dries, yet we are all as healthy as we should be on the
mountains of Switzerland, whose inhabitants are not more so than those of
Bermuda or St. Helena, islands on whose rocks the waves are dashed into
millions of particles, which fill the air with damp, but produce no diseases,
the moisture being pure, unmixed with the poisonous vapours arising from
putrid marshes and stagnant pools, in which many insects die and corrupt
the water. These places only, in my opinion (which however I submit to
yours) afford unwholesome air; and that it is not the mere water contained
in damp air, but the volatile particles of corrupted animal matter mixed with
that water, which renders such air pernicious to those who breathe it. And I
imagine it a cause of the same kind that renders the air in close rooms,
where the perspirable matter is breathed over and over again by a number of
assembled, people so hurtful to health. After being in such a situation, many
find themselves affected by that febricula, which the English alone call a
cold, and, perhaps from the name, imagine that they caught the malady by
going out of the room, when it was in fact by being in it.
You begin to think that I wander from my subject, and go out of my
depth. So I return again to my chimneys.
We have of late many lecturers in experimental philosophy. I have
wished that some of them would study this branch of that science, and give
experiments in it as a part of their lectures. The addition to their present
apparatus need not be very expensive. A number of little representations of
rooms composed each of five panes of sash glass, framed in wood at the
corners, with proportionable doors, and moveable glass chimneys, with
openings of different sizes, and different lengths of funnel, and some of the
rooms so contrived as to communicate on occasion with others, so as to
form different combinations, and exemplify different cases; with quantities
of green wax taper cut into pieces of an inch and half, sixteen of which
stuck together in a square, and lit, would make a strong fire for a little glass
chimney, and blown out would continue to burn and give smoke as long as
desired. With such an apparatus all the operations of smoke and rarified air
in rooms and chimneys might be seen through their transparent sides; and
the effect of winds on chimneys, commanded or otherwise, might be shown,

by letting the entering air blow upon them through an opened window of
the lecturer's chamber, where it would be constant while he kept a good fire
in his chimney. By the help of such lectures our fumists would become
better instructed. At present they have generally but one remedy, which
perhaps they have known effectual in some one case of smoky chimneys,
and they apply that indiscriminately to all the other cases, without success,
—but not without expence to their employers.
With all the science, however, that a man shall suppose himself possessed
of in this article, he may sometimes meet with cases that shall puzzle him. I
once lodged in a house at London, which, in a little room, had a single
chimney and funnel. The opening was very small, yet it did not keep in the
smoke, and all attempts to have a fire in this room were fruitless. I could not
imagine the reason, till at length observing that the chamber over it, which
had no fire-place in it, was always filled with smoke when a fire was
kindled below and that the smoke came through the cracks and crevices of
the wainscot; I had the wainscot taken down, and discovered that the
funnel, which went up behind it, had a crack many feet in length, and wide
enough to admit my arm, a breach very dangerous with regard to fire, and
occasioned probably by an apparent irregular settling of one side of the
house. The air entering this breach freely, destroyed the drawing force of
the funnel. The remedy would have been, filling up the breach or rather
rebuilding the funnel: but the landlord rather chose to stop up the chimney.
Another puzzling case I met with at a friend's country house near
London. His best room had a chimney in which, he told me, he never could
have a fire, for all the smoke came out into the room. I flattered myself I
could easily find the cause, and prescribe the cure. I had a fire made there,
and found it as he said. I opened the door, and perceived it was not want of
air. I made a temporary contraction of the opening of the chimney, and
found that it was not its being too large that caused the smoke to issue. I
went out and looked up at the top of the chimney: its funnel was joined in
the same stack with others, some of them shorter, that drew very well, and I
saw nothing to prevent its doing the same. In fine, after every other
examination I could think of, I was obliged to own the insufficiency of my
skill. But my friend, who made no pretension to such kind of knowledge,
afterwards discovered the cause himself. He got to the top of the funnel by a
ladder, and looking down, found it filled with twigs and straw cemented by

earth, and lined with feathers. It seems the house, after being built, had
stood empty some years before he occupied it; and he concluded that some
large birds had taken the advantage of its retired situation to make their nest
there. The rubbish, considerable in quantity, being removed, and the funnel
cleared, the chimney drew well, and gave satisfaction.
In general smoke is a very tractable thing, easily governed and directed
when one knows the principles, and is well informed of the circumstances.
You know I made it descend in my Pensylvania stove. I formerly had a
more simple construction, in which the same effect was produced, but
visible to the eye (Plate, Figure 7). It was composed of two plates A B and
C D, placed as in the figure. The lower plate A B rested with its edge in the
angle made by the hearth with the back of the chimney. The upper plate was
fixed to the breast, and lapped over the lower about six inches wide and the
length of the plates (near two feet) between them. Every other passage of
air into the funnel was well stopped. When therefore a fire was made at E,
for the first time with charcoal, till the air in the funnel was a little heated
through the plates, and then wood laid on, the smoke would rise to A, turn
over the edge of that plate, descend to D, then turn under the edge of the
upper plate, and go up the chimney. It was pretty to see, but of no great use.
Placing therefore the under plate in a higher situation, I removed the upper
plate C D, and placed it perpendicularly (Plate, Figure 8) so that the upper
edge of the lower plate A B came within about three inches of it, and might
be pushed farther from it, or suffered to come nearer to it, by a moveable
wedge between them. The flame then ascending from the fire at E, was,
carried to strike the upper plate, made it very hot, and its heat rose and
spread with the rarefied air into the room.
I believe you have seen in use with me, the contrivance of a sliding-plate
over the fire, seemingly placed to oppose the rising of the smoke, leaving
but a small passage for it, between the edge of the plate and the back of the
chimney. It is particularly described, and its uses explained, in my former
printed letter, and I mention it here only as another instance of the
tractability of smoke[57].
What is called the Staffordshire chimney, (see the Plate, facing page 238)
affords an example of the same kind. The opening of the chimney is bricked
up, even with the fore-edge of its jams, leaving open only a passage over
the grate of the same width, and perhaps eight inches high. The grate

consists of semicircular bars, their upper bar of the greatest diameter, the
others under it smaller and smaller, so that it has the appearance of half a
round basket. It is, with the coals it contains, wholly without the wall that
shuts up the chimney, yet the smoke bends and enters the passage above it,
the draft being strong, because no air can enter that is not obliged to pass
near or through the fire, so that all that the funnel is filled with is much
heated, and of course much rarefied.
Much more of the prosperity of a winter country depends on the plenty
and cheapness of fuel, than is generally imagined. In travelling I have
observed, that in those parts where the inhabitants can have neither wood
nor coal nor turf but at excessive prices, the working people live in
miserable hovels, are ragged, and have nothing comfortable about them.
But when fuel is cheap (or where they have the art of managing it to
advantage) they are well furnished with necessaries, and have decent
habitations. The obvious reason is, that the working hours of such people
are the profitable hours, and they who cannot afford sufficient fuel have
fewer such hours in the twenty four, than those who have it cheap and
plenty: for much of the domestic work of poor women, such as spinning,
sewing, knitting; and of the men in those manufactures that require little
bodily exercise, cannot well be performed where the fingers are numbed
with cold, those people, therefore, in cold weather, are induced to go to bed
sooner, and lie longer in a morning, than they would do if they could have
good fires or warm stoves to sit by; and their hours of work are not
sufficient to produce the means of comfortable subsistence. Those public
works, therefore, such as roads, canals, &c. by which fuel may be brought
cheap into such countries from distant places, are of great utility; and those
who promote them may be reckoned among the benefactors of mankind.
I have great pleasure in having thus complied with your request, and in
the reflection, that the friendship you honour me with, and in which I have
ever been so happy, has continued so many years without the smallest
interruption. Our distance from each other is now augmented, and nature
must soon put an end to the possibility of my continuing our
correspondence: but if consciousness and memory remain in a future state,
my esteem and respect for you, my dear friend, will be everlasting.
B. FRANKLIN.

Notes for the Letter upon Chimneys.
No. I.
The latest work on architecture that I have seen, is that entitled Nutshells,
which appears to be written by a very ingenious man, and contains a table
of the proportions of the openings of chimneys; but they relate solely to the
proportions he gives his rooms, without the smallest regard to the funnels.
And he remarks, respecting those proportions, that they are similar to the
harmonic divisions of a monochord.[58] He does not indeed lay much stress
on this; but it shows that we like the appearance of principles; and where
we have not true ones, we have some satisfaction in producing such as are
imaginary.
No. II.
The description of the sliding plates here promised, and which hath been
since brought into use under various names, with some immaterial changes,
is contained in a former letter to J. B. Esq. as follows:

T O J . B . [ 5 9 ] E S Q . AT B O S T O N , I N N E W - E N G L A N D .

London, Dec. 2, 1758,
Dear Sir,
I have executed here an easy simple contrivance, that I have long since
had in speculation, for keeping rooms warmer in cold weather than they
generally are, and with less fire. It is this. The opening of the chimney is
contracted, by brick-work faced with marble slabs, to about two feet
between the jams, and the breast brought down to within about three feet of
the hearth. An iron frame is placed just under the breast, and extending
quite to the back of the chimney, so that a plate of the same metal may slide
horizontally backwards and forwards in the grooves on each side of the
frame. This plate is just so large as to fill the whole space, and shut the
chimney entirely when thrust quite in, which is convenient when there is no
fire. Drawing it out, so as to leave a space between its further edge and the
back, of about two inches; this space is sufficient for the smoke to pass; and

so large a part of the funnel being stopt by the rest of the plate, the passage
of warm air out of the room, up the chimney, is obstructed and retarded, and
by that means much cold air is prevented from coming in through crevices,
to supply its place. This effect is made manifest three ways. First, when the
fire burns briskly in cold weather, the howling or whistling noise made by
the wind, as it enters the room through the crevices, when the chimney is
open as usual, ceases as soon as the plate is slid in to its proper distance.
Secondly, opening the door of the room about half an inch, and holding
your hand against the opening, near the top of the door, you feel the cold air
coming in against your hand, but weakly, if the plate be in. Let another
person suddenly draw it out, so as to let the air of the room go up the
chimney, with its usual freedom where chimneys are open, and you
immediately feel the cold air rushing in strongly. Thirdly, if something be
set against the door, just sufficient, when the plate is in, to keep the door
nearly shut, by resisting the pressure of the air that would force it open:
then, when the plate is drawn out, the door will be forced open by the
increased pressure of the outward cold air endeavouring to get in to supply
the place of the warm air, that now passes out of the room to go up the
chimney. In our common open chimneys, half the fuel is wasted, and its
effect lost; the air it has warmed being immediately drawn off. Several of
my acquaintance, having seen this simple machine in my room, have
imitated it at their own houses, and it seems likely to become pretty
common. I describe it thus particularly to you, because I think it would be
useful in Boston, where firing is often dear.
Mentioning chimneys puts me in mind of a property I formerly had
occasion to observe in them, which I have not found taken notice of by
others; it is, that in the summer time, when no fire is made in the chimneys,
there is, nevertheless, a regular draft of air through them, continually
passing upwards, from about five or six o'clock in the afternoon, till eight or
nine o'clock the next morning, when the current begins to slacken and
hesitate a little, for about half an hour, and then sets as strongly down again,
which it continues to do till towards five in the afternoon, then slackens and
hesitates as before, going sometimes a little up, then a little down, till, in
about a half an hour, it gets into a steady upward current for the night,
which continues till eight or nine the next day; the hours varying a little as
the days lengthen and shorten, and sometimes varying from sudden changes
in the weather; as if, after being long warm, it should begin to grow cool

about noon, while the air was coming down the chimney, the current will
then change earlier than the usual hour, &c.
This property in chimneys I imagine we might turn to some account, and
render improper, for the future, the old saying, as useless as a chimney in
summer. If the opening of the chimney, from the breast down to the hearth,
be closed by a slight moveable frame or two, in the manner of doors,
covered with canvas, that will let the air through, but keep out the flies; and
another little frame set within upon the hearth, with hooks on which to hang
joints of meat, fowls, &c. wrapt well in wet linen cloths, three or four fold, I
am confident, that if the linen is kept wet, by sprinkling it once a day, the
meat would be so cooled by the evaporation, carried on continually by
means of the passing air, that it would keep a week or more in the hottest
weather. Butter and milk might likewise be kept cool, in vessels or bottles
covered with wet cloths. A shallow tray, or keeler, should be under the
frame to receive any water that might drip from the wetted cloths. I think,
too, that this property of chimneys might, by means of smoke-jack vanes,
be applied to some mechanical purposes, where a small but pretty constant
power only is wanted.
If you would have my opinion of the cause of this changing current of air
in chimneys, it is, in short, as follows. In summer time there is generally a
great difference in the warmth of the air at mid-day and mid-night, and, of
course, a difference of specific gravity in the air, as the more it is warmed
the more it is rarefied. The funnel of a chimney, being for the most part
surrounded by the house, is protected, in a great measure, from the direct
action of the sun's rays, and also from the coldness of the night air. It thence
preserves a middle temperature between the heat of the day, and the
coldness of the night. This middle temperature it communicates to the air
contained in it. If the state of the outward air be cooler than that in the
funnel of the chimney, it will, by being heavier, force it to rise, and go out at
the top. What supplies its place from below, being warmed, in its turn, by
the warmer funnel, is likewise forced up by the colder and weightier air
below, and so the current is continued till the next day, when the sun
gradually changes the state of the outward air, makes it first as warm as the
funnel of the chimney can make it (when the current begins to hesitate) and
afterwards warmer. Then the funnel, being cooler than the air that comes
into it, cools that air, makes it heavier than the outward air, of course it