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Title: Mechanics: The Science of Machinery

Author: A. Russell Bond

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*** START OF THE PROJECT GUTENBERG EBOOK MECHANICS:
THE SCIENCE OF MACHINERY ***

Copyright, Ewing Galloway

The drop forge. A fourteen-ton hydraulic press is employed in
forging an immense open hearth steel plate.

Popular Science Library

EDITOR-IN-CHIEF

GARRETT P. SERVISS

AUTHORS

WILLIAM J. MILLER HIPPOLYTE GRUENER A. RUSSELL BOND
D. W. HERING LOOMIS HAVEMEYER ERNEST G. MARTIN
ARTHUR SELWYN-BROWN ROBERT CHENAULT GIVLER
ERNEST INGERSOLL WILFRED MASON BARTON
WILLIAM B. SCOTT ERNEST J. STREUBEL
NORMAN TAYLOR DAVID TODD
CHARLES FITZHUGH TALMAN
ROBIN BEACH

ARRANGED IN SIXTEEN VOLUMES
WITH A HISTORY OF SCIENCE, GLOSSARIES
AND A GENERAL INDEX

ILLUSTRATED

VOLUME FIVE

P. F. COLLIER & SON COMPANY
NEW YORK

Copyright 1922
By P. F. Collier & Son Company

MANUFACTURED IN U. S. A.

MECHANICS

The Science of Machinery

BY

A. RUSSELL BOND
Formerly Managing Editor, Scientific American

P. F. COLLIER & SON COMPANY
NEW YORK

PREFACE

A
LTHOUGH strictly speaking the term “Mechanics” applies to that branch
of Physics that deals with the actions of forces on material bodies,
originally the word had a broader meaning embracing all machinery
and mechanical inventions. To-day popular usage is restoring to the
term its original broad interpretation, and it is in this popular but rather
unorthodox sense that “Mechanics” has been chosen as the title of this
book; for although certain elementary principles of mechanics are described
and explained, the major portion of the book deals with machines and their
evolution to their present stage of perfection.
Machines are man’s creation, and yet in a sense the man of to-day is a
machine product; for modern civilization owes its material and in large
measure its esthetic development to machinery. The story of machinery,
from primitive man’s first attempts to augment his physical powers with
mechanical aids down to the present era of gigantic, steel-muscled
machinery and marvelously intricate mechanisms, is the story of human
progress. It is this story that we have endeavored to tell in the following
pages, but the subject is too large to be covered in a single volume or even a
dozen volumes. Under the circumstances we have been obliged to confine
ourselves to a mere outline, selecting certain avenues of progress more
marked than others and presenting brief sketch maps of them. We have
aimed in this way to give a bird’s-eye view of the whole story of human
progress in things material.
The book has not been written for the mechanical engineer, but for the
layman who would learn of the mechanical contrivances that contribute to
his material welfare; hence technical terms have been avoided, as far as
possible, and where unavoidable have been explained and defined.
A. Russell Bond

CONTENTS
CHAPTER PAGE
I. Tool-Making Animals 9
II. The Anatomy of a Machine 20
III. Machines for Making Machines 42
IV. Counting Seconds 57
V. Putting Rivers to Work 75
VI. Liquid Levers and Gears 94
VII. Air vs. Water 109
VIII. Air Springs and Cushions 126
IX. Power from Heat 139
X. Burning Fuel in the Engine Cylinder 155
XI. When Coal and Oil Are Exhausted 171
XII. Invasion of the Sea 182
XIII. Sliding, Rolling, Walking, and Creeping 203
XIV. Invasion of the Sky 219
XV. Helping the Farmer 239
XVI. Machining the Earth 251
XVII. From Fiber to Fabric 268
XVIII. The Making of Paper 289
XIX. Typesetting and Printing Machinery 300
XX. Cast Iron, Wrought Iron, and Steel 314
XXI. Animated Machinery 326
XXII. Heat Vacuums 345

XXIII. Engines of Destruction 359
XXIV. Summary of Mechanical Progress 376

LIST OF ILLUSTRATIONS
The Drop Forge—Forging a Steel Plate Frontispiece
FACING
PAGE
Raising Water with a Chain of Pots—a
Primitive Pump Used in Egypt 32
Horse-Operated Chain Pump Used in Greece 32
Multiple Spindle Drill in a Motor Car
Factory 33
Bucket of a Giant Dredge with Its Jaws
Wide Open 64
Gold Dredge Eating Its Way Through River
Sands 65
Suction Dredge Excavating a Channel and
Building New Land 65
Air Lock of a Pneumatic Caisson 96
Subaqueous Tunnel Showing the Shield in
the Background 97
Wharf Protected by a Pneumatic
Breakwater 128
Sun-Power Plant in Egypt 129
Close-Up of One of the Reflectors of a Sun-
Power Plant 129
Giant Caproni Hydroaeroplane 160
Concrete Steamship “Faith” 161

“Virginian,” the Largest Locomotive in the
World 161
Loom Provided with a Jacquard Attachment 224
Battery of Mule Spinning Frames 225
Jacquard Attachment for Loom 225
Digging a Trench with a Machine of the
Chain Type 256
Multiple Plowing on a Western Wheat Field 257
Sawing Logs of Pulpwood into 16-Inch
Lengths 288
Heater in a Pulp Mill Where the Wood Pulp
Is Mixed with Clay 288
Modern Fourdrinier Paper-Making Machines 289
Molten Metal from a Blast Furnace 320
Bessemer Converter Blowing Air Through a
Mass of Molten Iron 320
Steel Beam Passing Through the Finishing
Rolls 321
Compositor at Work on a Linotype Machine 352
The Optophone, Which Enables the Blind to
Read Print 353
Blind Man Reading with His Ears 353

CHAPTER I

TOOL-MAKING ANIMALS

W
HEN we review the marvelous achievements of modern
civilization we are quite willing to agree with the ancient
psalmist that man is “little lower than the angels.” But at the
other end of the scale our complacency is liable to receive a rude
shock; apparently the boundary between man and beast is not so very easy
to draw.
We used to be told that one important superiority of mankind lies in the
fact that he makes use of tools, while the beast never uses any implement
except those that nature has furnished him as part of his own organism. But
a gorilla will throw stones at his enemy; and he knows how to brandish a
club and use it with telling force. Some of the apes are known to use sticks
to knock down fruit which is out of the reach of their hands, and they will
crack nuts with a stone. Clearly these animals are tool users. A very
intelligent orang-utan in the Bronx Zoölogical Garden, New York, after
trying for days to wrench off a bracket from the wall of his cage eventually
used the horizontal bar of his trapeze as a lever and with it pried the
offending bracket from its fastenings. Here was real invention and the
discovery of the principle of leverage. The great black arara cockatoo of
New Guinea uses his beak as a saw to weaken the shells of hard nuts, and to
keep his bill from slipping off the smooth shell he is ingenious enough to
wrap a leaf around the nut to hold it steady.
Even in the insect world we find creatures resourceful enough to make
use of tools. Prof. Franz Doflein of the University of Breslau tells of an
interesting study of certain ants, known as the Oecophylla smaragdina, who

build their nests in bushes by fastening leaves together with fine threads.
But the ants that build the nests cannot spin these threads, because they
possess no spinning glands. They must depend upon their larvæ for this
product. When a rent was made in one of these nests, a band of the tiny
creatures ranged themselves side by side along the torn edge of the leaf and
reached across the gap until they could catch hold of the opposite edge with
their mandibles. Then they drew back step by step, with perfect teamwork,
until the two edges were brought together. In the meantime, other ants had
rushed to the nursery and each one had picked up a larva, not with the idea
of bearing it off to safety, but in order that the babies might spin the thread
which the adult ants were unable to do. The larvæ were carried to the
breach in the nest and moved back and forth across the rent. They were
pressed first against one side of the tear and then the other and all the while
were squeezed tightly, evidently with the purpose of making them spin.
Gradually a fine silky web was woven across the torn leaf and eventually
the rent was completely patched.
Unquestionably these little ants are tool-using animals, because they
make their larvæ serve as spinning spindles and also as weavers’ shuttles.
However, this can hardly be cited as a point in common with even the
lowest type of man, for the ants merely use the tools they find at their
disposal. They certainly cannot be credited with having produced or even
improved the tool which they use, whereas even in the most primitive of
men we find that the tools used are not only carefully selected for the work
to be performed, but are actually, shaped, be it ever so crudely, to suit the
job.
Clearly we must shift the boundary between man and beast,
distinguishing the former as the creature who artificially improves his tools.
But even here it is not absolutely certain that the boundary will stand.
Wilhelm Boelsche, a well-known German writer on natural history, calls
attention to the “blacksmith woodpecker” which will thrust hard pine nuts
into cracks in the trunk of a tree, so that they are held as if in a vise,
enabling the bird to operate upon the seed more easily. Furthermore, this
woodpecker will actually make a hole in the tree to receive the nut if there
is not a hole or crack handy, so that evidently this animal does produce or
artificially improve the tool that it uses.
There are a few such examples in nature, just enough to cast a bit of
uncertainty on the boundary we have set. But although the actual line of

demarcation may not be clear, there is no question but that the lowest type
of humanity now existent, or of which we have any record, is or was a tool
maker. Chipped stones evidently fashioned by man for some useful purpose
are found even in the remains of the Middle Tertiary Epoch. The spirit of
inquiry, of experiment, of invention, and the ambition to dominate over
other members of the animal kingdom or over the obstacles imposed by
nature, are to be found more or less active among all peoples, no matter
how lowly a position they may occupy in the scale of civilization.

WAR AS A STIMULUS OF INVENTION

The most primitive implements were probably developed for the
purpose of war. From the very earliest times, down to the present day, war
has been a most potent stimulus of invention. The first tools ever used were
probably intended to enable the user to cope with dangerous enemies. They
marked the first stage in the conquest of brain over mere brawn. The
primitive weapons were used not only in fighting other men, but in fighting
off dangerous animals, and then in hunting animals for food. No doubt the
first implement ever used was a club, which gave a real advantage over the
unarmed, scratching, tearing, and biting enemy. This was a lever which
increased the reach of the fighter, and also increased the power of his blow.
The heavier the club, the more dangerous the weapon, particularly when
most of the weight was centered at the outer end of the stick. But he was a
real genius who first fastened a rock to the end of his club.

THE ART OF BREAKING STONES

Then arose the art of breaking stones—breaking them skillfully, so as to
form a jagged cutting edge. When man began to fashion tools of stone he
left imperishable records of his craftsmanship which enable us to trace his
progress in invention. The first finished tool we find was the fist hatchet—a
stone roughly chipped to form a cutting edge and of convenient shape for
the grasp of the hand. This primitive tool very slowly, through a period
covering thousands of years, developed into all manner of cutting
implements, some with handles of wood and bone. The ax head was
followed by the spearhead and this finally by the arrowhead, showing that
man had at last found a mechanical substitute for his muscles to hurl

projectiles farther and with greater accuracy than he could throw them by
hand.
We marvel at the resourcefulness and skill of the primitive savage in
working so difficult a material as stone. It would baffle a modern mechanic
to be required to shape a piece of flint into an arrowhead with no other tool
than a piece of bone. He is so accustomed to using tools which are harder
than the material they are intended to shape that he cannot conceive of
making any impression upon a piece of flint with a piece of bone, to say
nothing of a stick of hard wood, and yet such tools were used away back in
the Stone Age. At first stones were roughly shaped by hammering them
together. Then the artisans became more skilled. They discovered that
certain stones could be chipped more regularly and evenly, and the art of
flaking off chips of flint sprang up. Some specimens that belonged to ages
long preceding that of recorded history are beautifully done. The spearheads
are symmetrically shaped like a long narrow leaf, and the stone is evenly
furrowed on both sides with a keen edge all around.
Not only did primitive artisans shape the stone implements with
hammer blows, but they learned how to shape stone by pressure as well,
using a tool that was relatively soft. It is not a very difficult matter to shape
even so hard a substance as glass merely by pressure. If a piece of glass is
laid on a table with its edge slightly overhanging that of the table, it is
possible to chip off the overhanging edge by pressing a nail or even a hard
stick of wood against this edge. A small flake of glass is thus removed, and,
by continuing the process, arrowheads of any shape may be formed. The
tool is placed not against the upper surface of the glass, but against the edge
of the glass, so that only the lower surface of it is split or flaked off. Then
the glass is turned over and a chip is taken off the opposite face.
In the Middle Stone Age we find the primitive craftsman equipped with
a very complete assortment of stone tools. He had hammers, chisels,
scrapers, drills, and polishing tools. He knew how to make useful household
implements, such as spoons and ladles, out of bone. He polished his work
and ornamented the implements with carvings of animals. Ivory pins and
needles show that he had begun to make himself clothing from the skins of
animals and that he sewed them together with thongs or tendons.
In the Late Stone Age he had learned how to make vessels of fire-baked
clay. His axes were ground to a sharp edge, and he bored holes in the ax

head to receive the ax handle. The Swiss lake dwellers built houses of wood
and fitted them with all sorts of wooden furniture carved with stone tools.
Among the remains of these interesting settlements may be found balls of
clay which, from the fact that one of them was discovered with a spool of
flax still attached to it, were evidently used as spinning “whorls” used for
spinning flax into thread. Clothing of skins was giving way to or being
supplemented with clothing of woven fabric.

DISCOVERY OF THE LEVER AND THE WEDGE

Prior to the Stone Age the club was undoubtedly used, in time of peace
—if there ever was a time of peace in those days—to batter down trees, to
beat through entanglements and to dislodge great stones. Here the first idea
of leverage was evidently employed. The club with a rock tied to it,
particularly if the rock was shaped with a sharp edge, made a better
implement for hewing trees. It is quite probable that soon after this stage of
development had been reached, some one discovered the use of the wedge,
particularly in splitting timber. Of course, no one realized in those early
days why it was that he could pry up a greater weight with a lever than he
could lift directly by hand, or why he could split open a log by driving
wedges into it. The art of mechanics was in existence long ages before
science of mechanics began to be studied. But it was not until men began to
look into the why of things that rapid progress was made.
We can go on endlessly with our speculations on the evolution of tools
and machinery up to the time when historians began to record the
mechanical achievements of man. Unfortunately even after historians began
to write they were so filled with admiration for the destructive work of man
that they had no time to record his constructive work. The warrior who
spread havoc and terror received all the glory, and his deeds were written on
parchment, inscribed in clay and carved in stone; but the humble artisan
was not worthy of mention. Even when the science of mechanics came to
be studied, it was shrouded in a veil of mystery, and it was beneath the
dignity of the man of science to impart his knowledge to the artisan. There
was a lack of cooperation between science and industry that has persisted to
a certain extent even up to the present time. Some of the most ingenious
inventions of the ancients were employed by a corrupt and crafty priesthood
to produce apparently miraculous effects and hoodwink the general public;

and so, in looking back to the early days of mechanics, we are obliged to
draw upon our imagination to trace its evolution, supplementing this by a
study of the tools of primitive people of more recent time. Practically every
form of hand tool we now use must have been known to the ancient artisan.

INVENTION OF THE WHEEL

We are not going to attempt to write a history of the evolution of
machinery, but there is one invention whose origin is lost in the remote
prehistoric ages which deserves more than passing attention. It is a pity that
we have no clue as to who invented the wheel or how this most important
element that enters into the construction of nearly all machinery was
evolved. The invention called for a remarkable degree of originality. There
is nothing like a wheel in nature. Levers we have in our own physical
frame. But a wheel is something that is distinctly a human creation.
Whoever invented it must have been a real genius, a James Watt or a
Thomas Edison of his day. Certainly we owe more to the invention of the
wheel than we do even to so revolutionary a machine as the steam engine,
or the flying machine. How it was ever first conceived is a mystery. Maybe
this primeval genius got his idea from seeing a stone rolling downhill, or he
may have seen a tumbling weed rolling along the ground before the wind. It
may be that the forerunner of the wheel was a roller shaped out of a log, for
certainly primitive civilization must have advanced enough to have known
how to hew timber before it would have been capable of fashioning a
wheel. Some observant man might have noticed that he could drag a heavy
timber over a rolling log much more easily than he could along the bare
ground, and gradually the roller evolved into a wheel.
We can speculate upon the evolution of vehicles and transportation,
once the wheel was invented. Of course, the first method of transporting
loads was to carry them in the arms. Possibly loads were placed on skids
and dragged along by one end. Away back in early times, it was discovered
that two persons could carry more than twice as much as one, if the load
were placed on a couple of poles. There was no friction to contend with,
and not only was the load cut in two, because each man bore half of it, but
the position of the load was such that it could be borne more easily. After
the wheel was discovered, some one must have conceived of the idea of
dispensing with an assistant by placing a wheel between the poles of the

stretcher, thus making a crude wheelbarrow. It is more likely that two
wheels were first used, making a cart of the stretcher, because the crude
workmen of those days could hardly have produced anything but a very
wobbly wheelbarrow. At any rate, the wheel, or pair of wheels, robbed one
man of his job. Only one bearer was required where before two had been
used. Labor costs were immediately reduced 50 per cent.

DISPLACING MEN WITH MACHINES

In the very earliest days of invention machines began to displace men.
Had there been unions in those days, no doubt there would have been
strenuous opposition to the introduction of this substitute for an honest
worker. But among the ancients, even more than at the present time,
invention meant greater production rather than less work, because the
laborer of that time was not a hired man but a slave. There was no object in
cutting down labor when it cost practically nothing. The only stimulus to
invention was greater production.
The invention of the wheel meant the dawn of transportation, which is
the backbone of civilization, and from it resulted no end of other inventions.
It made it possible for communities to come into closer touch with each
other. It meant circulation—an interchange of knowledge and of products.
Food was transported from one locality to another, enabling certain
communities to dispense with agricultural work and specialize in certain
lines of manufacture; for they could barter their products for food raised by
other communities. There are some tribes to-day which are most backward
because they are separated from other tribes by rivers, while other tribes
similarly placed owe their progress to the fact that they have developed
sufficient skill to build crude bridges and thus gain access to the outside
world.

RAISING WATER

In Egypt the wheel had a wonderful effect on agriculture. In that dry
land water is, and always has been, most precious. No wonder the Nile was
venerated! It meant life—life to crops, and hence life to man. How to raise
water from this stream of life in time of drought was the great problem of
the Egyptian. As slave labor was cheap, it was customary to haul up the

precious water, a bucket at a time, and pour it over the fields. Then some
one discovered that this process could be simplified by using a shadoof or
swape; in other words, a long pole fulcrumed near one end, with a heavy
rock for a counterbalance lashed to the shorter arm, and a bucket tied by a
long rope to the longer arm of the lever. This primitive machine is still to be
found in some rural districts. With this contrivance, a heavier load could be
lifted than by hand, because, when raising the bucket, the weight of the rock
would assist in lifting the water. After the swape came all manner of
ingenious devices for lifting the water. There were seesaw arrangements
which would scoop up some of the water at each oscillation of the seesaw,
and in one ingenious contrivance there was a succession of seesaws by
which the water was raised to a considerable height, whence it poured down
into ditches that irrigated the fields.
Then some one invented a water wheel or a great wheel, fitted with
buckets, which was turned by human or ox power, and which poured a
steady stream of water into the irrigating ditches.
But the greatest invention was that of the engineer who actually made
the river turn the wheel. It was probably on the Nile that the noria, as this
machine was called, was first put into service.
The wheel was provided with paddles, so that the current made it
revolve, and the water spilled out of the buckets into a trough as they were
turned over by the wheel. We can imagine the triumph of the ancient
inventor who developed that machine. True, the river might arise in its
wrath now and then and wreck the machine, but in wrecking the wheel it
had to flood the land, which, after all, was exactly what was aimed at. The
anger of the river was short-lived; it soon quieted down and went on
placidly turning the wheel which robbed it of the precious water. It was a
great event in the history of engineering. The Nile had been harnessed. One
of the great powers of nature had been set to work.

CHAPTER II

THE ANATOMY OF A MACHINE

E
VERY animal is a complex machine, provided with its own motive
power and a brain for directing the operation of its own mechanical
elements. Not satisfied with the mechanism that nature has put into the
human machine, man has reached for other elements and devised
mechanisms of his own in order to supplement the human machine and
increase its efficiency. At first, as we have seen, these elements were hand
tools of the crudest sort; but they were gradually improved and then they
were combined into what we term machines. In developing these machines,
he naturally took his own system as a pattern and was guided to a large extent
by an examination of his own physical structure. We see this very clearly in
the names of the different parts of machinery, which are taken from the
names of similar parts in the human frame. Almost every member of the body
is used in mechanical terminology. For instance, we have the “head” and the
“foot,” the “arms” and the “legs,” the “fingers” and the “ankles,” “elbows,”
“shoulders,” “trunk,” “hips,” and various parts of the face, such as the “eyes,”
“ears,” “nose,” “mouth,” “teeth,” “lips,” and even the “gums,” to indicate
parts of machinery which have some remote resemblance to these features.
Before we can understand machinery we must have some general
knowledge of the elements of which it is composed. Probably most of the
readers of this book already possess a fair knowledge of machine elements
and mechanical movements and they can well afford to skip this chapter.
However, for the benefit of the uninitiated, we must put a machine on the
operating table, dissect it, and explain its anatomical structure. We cannot
attempt a very detailed study, but will confine ourselves to the most important
elements.

Every machine is made up of movable parts and fixed parts, the latter
serving to guide or constrain the motion of the former; for no combination of
elements will constitute a machine unless the parts are constrained to move
in certain predetermined directions.

THE LEVER

Among the moving elements the first to be considered is the lever, which
really forms a broad classification comprising many elements that will hardly
be recognized as levers at first blush. Levers in some form are to be found in
practically every machine. A wheel, a gear, and a pulley are really levers in
disguise, as will be explained presently.
Of course everyone knows that a simple lever consists of a rigid bar that
swings on a fulcrum. The fulcrum may be a knife edge, a shaft passing
through the bar or any element on which the bar can be swung or oscillated.
The purpose of the lever is to give a certain advantage in the application of a
force to a load. This may be a change of speed and distance of travel, and
hence of power, or merely a change of direction.

FIG. 1.—THREE ORDERS OF SIMPLE LEVERS

There are three types or orders of levers produced by varying the relative
positions of the points where the fulcrum, the force or effort, and the weight
or load are applied. These are shown in Figure 1. In the lever of the first
order the fulcrum is placed between the effort and the weight; in the lever of
the second order the weight is applied between the fulcrum and the effort;
and in the lever of the third order the effort is applied between the fulcrum
and the weight. In each case that part of the lever which extends from the
fulcrum to the point where the effort is applied is called the effort arm, and
that which extends from the fulcrum to the point where the weight is
supported is the weight arm. The weight that can be lifted with a given effort
depends upon the ratio of the effort arm to the weight arm. If the two arms
are of equal length, the effort is equal to the weight, but twice the weight can
be lifted with the same effort if the effort arm is twice as long as the weight
arm. You can lift a ton with an effort of only 100 pounds if your effort arm is
twenty times as long as your weight arm but the end of your effort arm would
have to move twenty inches to raise the ton weight one inch. We are
assuming in all these cases that the lever itself has no weight and that there is
no friction at the fulcrum.
Of course levers are not used merely for the purpose of lifting weight, but
to overcome any resistance or merely to apply pressure upon an object. In
almost every household we may find examples of the three orders of levers.
A pair of shears, for instance, is composed of two levers of the first order,
swinging on a common fulcrum. The effort is applied at the handles, and the
weight or load is the material that is cut by the blades or, speaking more
technically, the handles are the effort arms and the blades are the weight
arms. A material that is too tough to be cut at the tip ends of the blades may
be easily cut if we move it in near the fulcrum or pin that hinges the blades
together; for by doing this we shorten the weight arms, because the weight
arm is measured not to the end of the blade, but to the point where it is
cutting into the material. To cut very tough material, such as heavy tin or
sheet steel, we use long-handled short-bladed shears. The cutting pressure
depends upon the ratio of the effort arm to the weight arm. If the effort arms
are twice as long as the weight arms, the cutting pressure is twice as great as
that applied at the handles.
A nutcracker consists of a pair of levers of the second order. The fulcrum
is at one end and the effort or pressure is applied at the opposite end of the
levers or handles, while the equivalent of the weight (in this case the nut) is
placed between the effort and the fulcrum. Again the effort arm is measured

from the fulcrum or hinge pin of the tool to the point where the hand pressure
is applied, and the weight arm is measured from the fulcrum to the nut. The
effort arm may be four or five times as long as the weight arm, so that the
pressure exerted on the nut is four or five times as great as that exerted by the
hand on the ends of the handles.

FIG. 2.—AN ANGULAR OR BELL-CRANK LEVER

In the case of a pair of sugar tongs we have another tool something like
the nutcracker in construction, but here the weight, i.e., the lump of sugar, is
seized by the ends of the tongs while the hand pressure is applied somewhere
between the fulcrum and the weight. Hence we have here a lever or pair of
levers of the third order. The effort arm of a pair of tongs is always shorter
than the weight arm and the pressure on the sugar lump is always less than
that exerted on the tongs by the hand. Evidently the most powerful tool of the
three is the nutcracker, because the effort arms extend over the full length of
the tool and are always longer than the weight arms.
A lever need not consist of a straight bar; the effort arm may form an
angle with the weight arm, forming what is known as an angular or bell-crank
lever (Figure 2). When a common claw hammer is used to pull out a nail, the
claws that slip under the head of the nail form the weight arm and the
hammer handle the effort arm. A horizontal pull on the handle produces a
vertical lift on the nail.

Sometimes two or more levers are interconnected, as in Figure 3, the
effort arm of one being linked to the weight arm of the other. This serves to
increase the lifting force at the weight and at the same time keep the
mechanism within compact limits. Such compounding can go on indefinitely
and is subject to all sorts of variations.

FIG. 3.—COMPOUND LEVERAGE

One thing we must not forget, and it is a matter that is commonly
overlooked by perpetual motion cranks, namely, that while a pound of
pressure on the effort arm may be made to lift two, four, or a hundred times
as many pounds on the weight arm by varying the relative length of these
arms, it has to move two, four, or a hundred times as far as the weight arm, so
that the work done on one side of the fulcrum is always exactly equal to that
done on the other side.

CONTINUOUS REVOLVING LEVERAGE

FIG. 4.—PRIMITIVE GEAR WHEELS—TWO COACTING
GROUPS OF LEVERS

If we take a number of levers radiating from a common fulcrum like the
spokes of a carriage wheel, we have a primitive gear wheel. Two such groups
of levers may be mounted on parallel shafts so that when one is turned its
spokes will successively engage the spokes of the other group and make the
latter turn (see Figure 4). Each spoke is first an effort arm on one side of the
wheel and then a weight arm as it turns around to the other side of the wheel,
and as the effort arms and weight arms are of the same length there is no
multiplication of power. A pound on one side of the wheel cannot lift more
than a pound on the other. The driven wheel receives the same power as the
driving wheel except for such loss as may be due to friction at the bearings or
where the spokes contact. The only advantage of such a pair of gears is that
the direction of rotation of the driven wheel is the reverse of that of the
driving wheel. If the spokes of one wheel are longer than those of the other,
we have at once a variation in the rate of rotation proportional to the relative
diameters of the two wheels. In Figure 5, for instance, the diameter of the
driving wheel A is twice the diameter of the driven gear B, and so, for each
revolution of A, B must make two revolutions, i.e., the driver must make two
revolutions for each revolution of the driven wheel. In other words, the speed
of revolution is doubled. However, if we make B the driver the speed of the
driven wheel A will be half of that of wheel B.

FIG. 5.—COACTING LEVERS OF UNEQUAL LENGTH

In primitive machines spoke gears were seldom mounted on parallel
shafts because of the difficulty of keeping the spokes in alignment. Instead,
one shaft was mounted at right angles to the other so that one set of spokes
would cross the other (Figure 6), thus producing the equivalent of a bevel
gear. This was of advantage in changing the plane of rotation. A later
development was the barrel or lantern gear, which permitted transfer of
power without changing the plane of rotation. A cylindrical bundle of rods
constituted one of the wheels (as shown in Figure 7). Instead of being crudely
formed of spokes, the other wheel sometimes consisted of a disk with pins
radiating from its rim. Such gears in far more refined form are still used in
modern clocks and watches. A still further development for transmitting
motion to a plane at right angles to that of the driving shaft is shown in
Figure 8. Here we have a crown gear in which the pins instead of radiating
from the periphery of the disk project from the side face of the gear.

Turning back to our first
spoked wheels, it is very evident
that we may put a rim over the
spokes or even fill in between the
spokes and convert the wheels
into solid disks that are in
frictional engagement with each
other without getting away from
the fact that we are dealing with
levers. Each wheel, then, consists
of a continuous revolving lever.
Friction gears are used quite
commonly in machinery when it
FIG. 6.—PRIMITIVE is desirable to have the wheels
EQUIVALENT OF THE BEVEL slip if subjected to excessive
GEAR strain.

FIG. 7.—PRIMITIVE LANTERN
GEAR
TOOTHED GEARS

By forming teeth on one gear to mesh between similar teeth on the other,
we convert the friction gears into a pair of spur gears (Figure 9). We need not
go into the intricacies of the form of gear teeth. They are designed to be in
continuous rolling contact while they are in mesh. The novice is apt to call all
spur gears “cogwheels” and gear-teeth “cogs.” Mechanics, however,
recognize a difference between cog wheels and spur wheels. In the former,
the teeth, or cogs, are not cast upon or cut out of the wheel body, but are
separate pieces fitted to the wheel. Such wheels are found in old water mills.
They consist of wooden wheels with iron or steel teeth mortised in the
wooden rim of the wheel. In general it is safer to speak of spur gears because
there are few cogwheels now in use.

FIG. 8.—CROWN AND LANTERN GEAR

When a small gear engages a large one, the former is commonly known
as a pinion.

FIG. 9.—SPUR AND PINION GEAR

FIG. 10.—BEVEL FRICTION GEARS

If two friction wheels are to turn at right angles one to the other, they
must have conical bearing surfaces, as in Figure 10. The angle between the
shafts of the two gears and the relative size of the gears may be changed as
desired, provided each cone surface has its apex at the intersection of the two
shafts or axes. It is easy to understand how such conical friction gears may be
converted into toothed bevel gears (Figure 11), by forming teeth on the
conical surfaces, and it will be evident that the teeth must taper toward the
apex of the two cones. Two bevel gears of equal diameter, and with shafts set
at right angles one to the other, are known as miter gears.

FIG. 11.—TOOTHED BEVEL GEARS

So far we have not shown any combination of gearing that will multiply
power. In Figure 5, the driver A is twice the diameter of the driven wheel B,
and the latter makes two revolutions for one of A, but the speed at the
periphery of the two wheels is the same. A pull of one pound at the point a
produces a pressure of one pound at b, and this in turn produces a lift of one
pound at c because the levers in each wheel are perfectly balanced, that is,
each lever has equal effort and weight arms. The way to obtain an increase of
power and of peripheral speed is to fasten two wheels of unequal diameters
together on the same center and apply the effort to one of the wheels (as in
Figure 12) and the weight to the other wheel. This gives us what is
technically known as a wheel and axle. The dotted lines show that we have
here a lever of the first order which can be used to multiply power in the
same way that a bar lever does. If one wheel is twice the diameter of the other
then a pound of effort will lift two pounds of weight.

FIG. 12.—WHEEL AND AXLE OR REVOLVING LEVER OF
FIRST ORDER

FIG. 13.—REVOLVING LEVERS OF THE 2D AND 3D ORDER

Figure 13 shows how the effort and weight can be shifted about in such
fashion as to give us a lever of the second and one of the third order. The
power may be enormously increased and the speed of the final wheel greatly
reduced by setting up a train of gears in which the effort is received by the
larger one of each couple and is delivered by the smaller one. In Figure 14
the smaller wheels are half the diameter of the larger ones. A pound of

pressure at A will amount to 2 at B, 4 at C, 8 at D, 16 at E, and 32 at F. On the
other hand, point A will have to move through 32 inches to make the point F
move an inch.

RAISING WATER WITH A CHAIN OF POTS
A primitive pump still used in Egypt

A HORSE-OPERATED CHAIN-PUMP USED IN GREECE

MULTIPLE SPINDLE DRILL IN MOTOR CAR FACTORY

FIG. 14.—A TRAIN OF SPUR GEARS

FIG. 15.—PULLEYS OF THE 1ST, 2D, AND 3D ORDERS

FIG. 16.—TYPICAL
ARRANGEMENT OF BLOCK AND
TACKLE

A pulley is merely a modification of the wheel. Figure 15 shows how it
may be arranged to correspond to the three orders of simple levers. If the
pulley axis is fixed, as in the first order, the effort and weight arms are equal
and hence balanced. In the second order the wheel is bodily movable, hence
one pound will raise two pounds of weight because the power arm is twice as
long as the weight arm, while in the third order it takes two pounds of lift to
raise one pound of weight. There is no end of possible combinations of
pulleys which will multiply power in the same way that bar levers do when
compounded. A common arrangement of block and tackle is given in Figure
16. There is a four-sheave pulley block above and a three-sheave block
below, but in order to trace the rope clearly the pulley wheels or sheaves are
represented as of different diameters. The arrangement consists of a series of
levers of the first order in the upper pulley block coupled to a series of levers
of the second order in the lower block. To find the weight that a given power
will lift, multiply the effort by the number of strands of rope that are
supporting the weight. In this case there are seven such strands, not counting
the strand E, to which the effort or pull is applied. This means that a pull of a
hundred pounds at E will lift 700 pounds at W. Of course a pull of seven feet
at E will raise the weight only one foot.

FIG. 17.—INCLINED PLANE WITH EFFORT PARALLEL TO
THE INCLINED FACE

THE INCLINED PLANE AND ITS FAMILY

The inclined plane constitutes a second broad classification of machine
elements. The wedge, the screw, the cam, and the eccentric, all belong to the
family of the inclined plane.

FIG. 18.—INCLINED PLANE WITH EFFORT PARALLEL TO
THE BASE

A simple form of inclined plane is pictured in Figure 17, which shows a
weight W being rolled up an incline. The effort required to carry it to the top
of the incline depends, of course, upon the steepness of the incline. The
drawing shows a rise of 3 feet on a slope 5 feet long, and the weight of the
wheel is, say 20 pounds. To find the effort required, the weight is multiplied
by the rise (20 × 3 = 60) and divided by the length of the slope (60/5 = 12)
and we find that it takes only 12 pounds to roll the 20-pound wheel to the top
of the incline. This holds true when the pull is parallel to the inclined face. If
the pull is parallel to the base of the incline, as in Figure 18, we must divide
by the length of the base instead of the length of the incline (60/4 = 15) and
we find that it takes 15 pounds of effort to pull the weight up the incline. If
the pull is exerted at an angle both to the base and the inclined face, we have
a problem that is slightly more complicated and we need not go into it here
because it involves a bit of trigonometry. In all cases, however, it may be
noted that the amount of rope that is taken in, in hauling the weight up the
incline, bears a definite relation to the amount of effort required to raise the
weight. In Figure 17, 5 feet of rope must be pulled in, in order to raise the
weight 3 feet, so that ⅗ of 20 or 12 pounds is all that is required to pull up
the weight, while in Figure 18, 4 feet of rope is hauled in for a lift of 3 feet,
so that ¾ of 20 or 15 pounds is required to pull up the weight. In this respect
the inclined plane is exactly like the lever or the pulley, for the effort
multiplied by the distance through which it is exerted is always exactly equal
to the weight multiplied by the distance through which it moves. Thus in
Figure 17, the effort 12 pounds multiplied by the distance 5 = the weight 20
pounds times the distance 3, and in Figure 18, effort 15 x distance 4 = weight
20 x distance 3. Of course, we are ignoring the weight of the rope and the
friction which, in actual practice, are important factors to be reckoned with.

FIG. 19.—ENDLESS SCREW OR WORM GEAR

So far we have considered a fixed inclined plane, but when the inclined
plane is moved between the weight and a fixed base it is known as a wedge,
and in this case, too, the effort required to move the wedge multiplied by the
distance the wedge moves is equal to the weight multiplied by the distance it
is lifted.
The commonest form of inclined plane is the screw which is merely an
inclined plane bent around a cylinder. A screw engaging a toothed wheel, as
in Figure 19, gives a combination known as an “endless screw,” or, more
commonly, as a worm gear. The screw or worm is always the driver, and as it
must make a complete turn to move the gear through a space of one tooth, the
power of this combination is very great. It is practically impossible to turn the
worm by using the gear wheel as a driver because the friction developed at
the point where the worm and gear contact is very great. For this reason
worm gearing is used in the steering gear of automobiles. The shaft of the
steering wheel is fitted with a worm which meshes with a worm gear on the

parts connected with the wheels. It is very easy to turn the wheels by
operating the steering wheel, but if the wheels strike a rut or a stone they are
not deflected from their course, because the worm makes it impossible for
them to turn the steering wheel.

FIG. 20.—HELICAL OR SPIRAL GEARS

The spiral gear shown in Figure 20 is a cross between a worm gear and
spur gear. The teeth are spirals set at an angle of 45 degrees to the axis of the
wheel. In this case either gear can be used to drive the other, and the
advantage of such a pair is that power is transmitted from one shaft to another
in a different plane and at right angles to the first.

FIG. 21.—DRUM CAM

FIG. 22.—PROFILE OR DISK CAM

Cams are usually irregular revolving inclined planes. Figure 21, shows a
cylinder or drum cam. A groove is cut in the cylindrical wall of the cam and
an arm or lever is provided with a roller which rolls in the groove. When the
cam is revolved the lever is constrained to follow all the twists and turns of
the groove. A different form of cam is shown in Figure 22. It is formed with
an irregular periphery against which the roller is pressed by a spring. As the
cam wheel revolves, the roller and the arm to which it is attached must move
in and out over all the hills and valleys of the periphery. The cam is one of
the most useful elements in modern machinery, for it provides a very simple
means of producing the most complicated and irregular motions.

FIG. 23.—ECCENTRIC BY WHICH ROTARY MOTION IS
CONVERTED INTO RECTILINEAR MOTION

We cannot attempt to describe all the different types of cams, but
reference should be made to the eccentric, which is a form of cam commonly
used to operate the valves of a steam engine. The cam in this case is a
perfectly circular disk, but the shaft that turns it does not lie at the center of
the disk, consequently an object bearing against the periphery must move
toward and away from the center as the disk revolves. Instead of using a
spring-pressed roller to bear against one side of the disk, the whole disk is
encircled with a ring of steel known as an eccentric strap. This strap is bolted

to a valve rod and as the eccentric revolves the strap makes the valve rod
move back and forth. (See Figure 23.)
A description of all the various combinations of gearing, link motions,
ratchets, escapements, clutches, and miscellaneous movements would easily
fill the rest of this book, and we must therefore content ourselves with this
very brief survey of a few of the more important elements employed in the
construction of modern machinery.

CHAPTER III

MACHINES FOR MAKING MACHINES

W
HILE we may glory in the wonderful mechanical progress of to-
day, we must not overlook the marvelous skill of the ancient
artisan nor forget that it is to his inventive genius that we are
indebted for practically every hand tool we possess. Only a few
special tools owe their origin to the modern inventor. All the rest date back
beyond the twilight of history. We have merely improved upon these tools by
slight changes of design or the employment of better materials in their
construction.
As users of these tools we cannot begin to compare with the skilled
workman of ancient days. Our progress is shown not in the development of
skill, but in the loss of it. We have taken the tool out of the human hand and
put it into an inanimate machine. It is only very recently that the tool was
delivered to the machine and that act marked the dawn of the present
remarkable mechanical era.
Machines for making machines date back to the time of the early
Egyptians. They had their pole lathes and bow drills, but these machines only
partially relieved the workman of his labors, and the quality of the work still
depended upon a degree of skill that was acquired only through years of
patient apprenticeship.
The pole lathe, by the way, consisted merely of a pair of centers between
which the work was mounted, a pole attached to the ceiling and a strap or
rope passed around the work and fastened at one end to a pole and at the
other to a pedal resting against the floor. (See Figure 24.) When the pedal was
depressed, the strap was pulled down and the work was revolved. On
releasing the pedal, the spring of the pole pulled the strap up and reversed the

rotation of the work. Thus by alternately depressing and releasing the pedal,
the work was intermittently revolved against a chisel which was rested on a
block and guided by the workman. Small work could be turned out on such a
lathe with considerable precision, but when it came to large parts, particularly
parts of steel, the workman was easily tired by the effort of operating the
pedal and was apt to be irregular in the guiding of the tool.

FIG. 24.—PRIMITIVE POLE LATHE

Up to the middle of the eighteenth century practically no advance had
been made over the ancient lathe of the Egyptians, and when, 150 years ago,
the steam engine was invented the task of building the engine seemed almost
insuperable.
James Watt was a maker of mathematical instruments, a man of great skill
and precision as a craftsman, but he dealt with parts of small dimensions.
When he conceived of his steam engine, he mentally pictured the various
parts as turned out with all the accuracy and finish that was possible in the
diminutive members of a scientific instrument. To him it seemed perfectly

feasible to turn a cylinder which would be practically perfect in contour, and
to fit it with a piston around which no steam could leak. With the lathe then in
existence such a fit was easily possible on small work. But when he
undertook to have the cylinder of his engine bored, he discovered that there
was no machine that could begin to do the work properly. In fact, when
Smeaton, who was a prominent engineer of that time, investigated Watt’s
steam engine, he declared that it was such a complicated piece of work that
neither tools nor workmen existed that could build it. In Watt’s first engine,
the cylinder was only six inches in diameter and two feet long, and a special
type of boring machine was devised to bore the forged cylinders. But the
boring was so irregular that when the piston was inserted and the steam was
turned on, nothing would stop the flow of steam that leaked around the
piston. In vain did James Watt use cork, oiled rags, tow, paper, and even old
hats to stop the leakage. However, the boring machine was improved and
later a cylinder, eighteen inches in diameter, was bored with such accuracy
that the large diameter exceeded the small diameter in the worst place by only
⅜ of an inch. This Watt considered a very good bit of turning. To-day
cylinders of that size that vary from true by half the thickness of the paper
that this is printed on would be thrown out as defective.
It was in 1769 that Watt invented the steam engine, but that great event
did not mark the dawn of the present era of machinery. For a quarter of a
century thereafter there was little progress in the development of machine
tools. A boring machine was built that did fair work. There were a few
sawmills in which wind power was employed to drive the saw. But lathes
were still driven by foot power and the cutting tool was still held and guided
by hand.

MAUDSLEY’S “GO-CART”

The real father of the present era was a very clever British mechanical
engineer, Henry Maudsley, who undertook to eliminate the uncertainties of
the human hand by clamping the cutting tool of the lathe in a rest and
arranging the rest to slide along the length of the lathe or transversely toward
or away from the center. These two motions made it possible to accomplish
all that the workman could accomplish by hand and at the same time the tool
was held so firmly that accuracy and precision of turning was assured.
Furthermore, he provided this slide rest with a nut that engaged a screw
driven through suitable gearing by the lathe spindle. Then, as the work

revolved, the slide rest was compelled to move along the bed of the lathe at a
uniform rate. By varying the gearing, the speed of the slide rest and the tool it
carried could be varied at will, thus making it possible to cut screw threads of
any pitch desired with a degree of accuracy unattainable by hand.
Remarkable as was this improvement, it met with the usual opposition
that every real advance in machinery received in those days. People referred
to the slide rest as Maudsley’s “go-cart,” but it proved such an important
element of the lathe and so very valuable that before long it was universally
adopted. From that time on the skill of the workman began to lose its
importance. The man began to give way to the machine. Precision was
possible in large as well as small work. The human element was also
dispensed with in the driving of the lathe. The foot pedal was superseded by
the steam engine, and the machine came to be known as the engine lathe.
There are many ways of working metals now in common use. Metals may
be cast in a molten state, or they may be pressed and molded into shape in a
cold state, or they may be hammered either cold or hot, but in nearly all cases
in which metal is removed in order to form a piece of work, the chisel is used
as a cutting instrument. This is perfectly apparent in lathes and planers, but
not quite so apparent in sawing, drilling, filing, and grinding. A drill is merely
a spiral chisel which revolves upon its own center. A saw is a gang of tiny
chisels, and a file consists of still smaller chisels which are broader than those
of the saw. In grinding we have rough surfaces in which particles of emery or
carborundum act as tiny chisels. The shears, the punch, and the cutting torch
are practically the only exceptions to the rule that metals are always cut by
chisels, and even the shears may be conceived as consisting of a pair of broad
coacting chisels, while it takes little imagination to see a form of chisel in the
punch. The cutting torch is, of course, in no sense a chisel.
In the cutting of metals the work may move against a fixed tool or the
tool may move against a fixed piece of work. In a lathe, it is the work that
revolves or rotates against the tool. In the drill and the milling machine the
tool revolves against the work.
In the planer, the tool is fixed and the work slides against it. The shaper
reverses the operation; the work is fixed and the tool moves in a rectilinear
direction.
Up to the nineteenth century practically the only machines for cutting
metals were the lathe and a crude form of boring machine. The machinists of
that day had not reached the stage where they were able to produce anything

but round work on a machine. The planer had not been born. It was for this
reason that Watt had a great deal of difficulty in getting rectilinear motion for
the piston of his engine. He had to invent a complicated system of links and
levers in order to obtain a practically parallel motion to guide his piston in
and out of the cylinder. When the planer was invented and it was possible to
produce straight surfaces with a considerable degree of accuracy, all of Watt’s
ingenious parallel motions, went into the discard and the cross-head and
guides took their place.
It was not until long after the planer had been invented that Eli Whitney,
the American genius of cotton-gin fame, conceived the milling machine. He
reversed the operation of the lathe by placing the cutting tool on the revolving
spindle and sliding the work against it. Milling cutters consist of wheels
formed with a number of cutting edges or chisels which are arranged either
on the periphery of the wheel or on the face of the wheel.
Following the milling machine, came the grinder, in which a revolving
wheel of an abrasive material served to wear away the surface of a piece of
work, and with this form of machine steels of great hardness could be
finished with accuracy and a high polish.

THE INTERCHANGEABLE SYSTEM

The most notable advance in machine work came early in the nineteenth
century, when what was known as the “American System” of manufacture, or
the interchangeable system, was introduced. As long as mechanics were
obliged to perform their operations largely by hand, it was impossible to
attain great accuracy. Each workman put his own individuality into the work.
As a consequence, no two pieces were of exactly the same size or shape. This
was true even with the early power-driven machine tools. The parts might be
very close to the same size, but careful measurements showed that they
varied by a minute fraction of an inch. Hence, when a machine was
assembled the unyielding metal parts had to be filed and trimmed and
hammered to fit them together. If any accident occurred to a machine, the
damaged part could not be replaced by another taken from stock. The entire
machine had to go back to the shop where an experienced mechanic would
make a new part to replace the damaged one. In those days a machine was
not manufactured but was built as an individual mechanism, just as a house
or a boat is built to-day.

With the advent of accurate machine tools came the idea of standardizing
the parts so that hundreds and thousands of pieces could be made of exactly
the same dimensions, and in assembling a machine the parts could be picked
at random from the stock and put together without the use of special tools and
without requiring any special fitting. This was of special importance in the
tools of warfare, because armies need quantity production, i. e., rifles,
cannon, etc. More machines of the same kind were required for an army than
for any other organization or line of work. At the close of the Napoleonic War
the British Government had 200,000 parts of muskets either partly finished or
waiting repairs. Their muskets were made after the old system. Each one was
built separately with its parts individually fitted together, so that whenever
any part was injured, the musket had to be laid aside and sent back to the
workshop for repairs.
Long before that time, the idea of making standard guns had been hit
upon in France. Thomas Jefferson, while Minister to France, in 1785, wrote
of the French system which was then being developed by a mechanic named
Le Blanc. He was building a musket in which the parts were of standard
pattern, and which could be assembled by taking pieces haphazard as they
came to hand and putting them together without special fitting. Thomas
Jefferson called the attention of the American Government to this system and
showed that it was possible to produce muskets cheaper by that method of
manufacture. However, our Government at that time failed to avail itself of
the opportunity of utilizing this system of manufacture.
Later on, the idea was taken up in this country by Eli Whitney and by
Simeon North. When Whitney attempted to introduce the system, he was
laughed at by French and English ordnance officials, and even our own
Government officials were skeptical, particularly when they found that it
required so much preparation in the way of machinery and designing of parts
before a single musket was completed. It seemed like a waste of money to
invest in so much preparation. But Whitney was soon able to silence all his
critics by taking to Washington ten pieces of each part of a musket and then
selecting at hazard from each pile of pieces the requisite parts and putting
together ten muskets. It was not long before the foreign governments saw the
importance of this method of manufacture. Great Britain later adopted it in
the making of her own rifles and called the process the “American System.”
But it was not only in the field of rifles that interchangeable manufacture
made itself felt. The New England clock industry provides an interesting

illustration. At first the clocks were made of wood, but early in the nineteenth
century, a clock maker, Chauncey Jerome by name, designed a brass clock in
which the parts were made on the interchangeable system. Instead of building
each clock as a separate piece of work, clocks were turned out by the
thousands, and at an extremely low price. Soon he had flooded this country
with his clocks and began to look around for other markets. Machinery had
been used by other clock makers in producing wooden clocks, and
movements which had cost $50 each in 1840 had been reduced to $5. But
Chauncey Jerome’s clock was made of brass and by means of the
interchangeable system of manufacture he could produce it for less than 50
cents. The clock was such a success in this country that Jerome decided to try
it abroad. Consequently he made arrangements with an agent in England and
shipped over a large consignment. The British Government was astonished at
the low price of the clock and was convinced that it had been undervalued. At
that time, they had a simple and ingenious method of punishing a consigner
who undervalued the goods he wished to introduce into the country. This
consisted in promptly appropriating the property at the price given in the
invoice. In due course of time, much to Jerome’s astonishment, he received a
letter from the British Government stating that his clocks had been
confiscated, and with the letter came a check paying for them at the invoice
price. Jerome was not in the least dejected by the rebuke; on the contrary, he
was rather elated, for, as far as he could figure it out, he had a spot-cash
buyer for his goods and no selling expenses. He did not mind at all letting the
British Government have the clocks at the invoice price. So he decided to try
again with a larger shipment. To his great delight this shipment met the same
fate as the first, and in due course another good British check arrived. Thus
encouraged, Jerome sent over a third and still larger shipment, but by that
time Johnny Bull began to suspect that the Yankee clock maker was getting
the best of the bargain and, finally convinced that clocks really could be
produced with profit at the low invoice price, he permitted them to enter his
country. With this striking example, the fame of the Yankee system of
manufacture spread over the world.
In order to have two parts alike, they must be placed under a machine in
exactly the same way. In other words, they must be set in “jigs” or frames
which are fitted into the machine in such a way that the tools will approach
the work from exactly the same angle or penetrate the work to exactly the
same depth in ten, or a hundred, or a thousand, or a million pieces, as the case
may be. Making jigs and dies consumes a great deal of time in preparation

work, but once the preparation stage has been passed, articles are produced
with wonderful rapidity and very little waste of time. Formerly it was
necessary to determine the location of each hole in a casting separately and
spend precious time in adjusting the work to the proper position under the
tool. If the hole was to be threaded, it had to pass through several separate
operations.

THE TURRET LATHE

After the slide rest invented by Maudsley, the next great improvement on
the lathe was a turret head or a sort of turntable which carried a number of
tools. The tools are arranged to come automatically into play one after the
other. One tool, for instance, may cut a groove in the work, another finish the
face of the work, another bore a hole in the piece and another tap the hole. In
many cases, several of these operations are performed simultaneously. The
head of the lathe is provided with a hollow spindle so that the work is
automatically fed to the tools through this spindle, and as soon as one piece is
finished, it is automatically cut off and the jaws of the clutch which holds the
work, or stock as it is called, open automatically so that a new length may
slide forward and be operated upon by the tools. The machine requires no
attention once the tools have been set up to the proper angle, except that it
must be kept supplied with bars of stock as they are consumed, and with a
copious flow of lubricant on the tools. One operator can therefore take charge
of a number of automatic lathes. All he does is to feed them; they do the rest.
The modern drill has also gone through a great many developments in
order to speed up the work that it performs. When a casting is to have forty or
fifty holes drilled and tapped in it, instead of following the old method of
drilling each hole separately, a lot of separate drilling spindles are used, each
fitted with a drill, and these are brought simultaneously into play. As many as
fifty or sixty holes may be drilled at a single operation, and after the holes
have been drilled, the drilling spindles move to one side to make way for the
taps, which thread such of the holes as are to receive screws. By first setting
the spindles in the proper position and then using jigs to locate the work
properly under them, the assurance is had that every one of the scores of
holes drilled will be accurately spaced apart and the spacing in every casting
will be identical.

The multiple tool system is also used in milling machines in which a
number of milling cutters either of the face or the end type come into play
simultaneously upon a piece of work set in a suitable jig, and cut the piece
with absolute precision, so that all castings will have faces accurately spaced
apart and cut to exactly the same level.
It is by such methods as these that we are able to produce such large
quantities of machinery at remarkably low cost. One of the most notable
examples of such work was the development of the Liberty engine during the
World War. This engine did not differ in principle from others built in Europe
or in this country, but its design was carefully adapted to permit of
interchangeable manufacture. No careful finish was used except where
indispensable. Special jigs, tools, and fixtures were prepared. Ingenious
wrinkles of American manufacture were introduced. All this consumed time,
and great was the irritation of the general public. Under ordinary conditions,
it would have taken years to have developed the Liberty engine to the
manufacturing stage, but under the urgent stress of war, the whole work of
design and preparation for manufacture was crowded into a few short
months, and then Liberty engines began to be manufactured on a stupendous
scale.

CUTTING WITH RED-HOT TOOLS

One of the most remarkable advances in machine tools was due to the
studies of Fred W. Taylor. He entered a large steel plant in 1880 and was
immediately struck with the enormous waste of effort on the part of the men
in the plant. There was at that time considerable dissatisfaction among the
workmen, and when Taylor endeavored to speed up work he was faced by the
incontrovertible argument that he had no idea how much work a certain
machine ought to turn out. There was nothing for him to do but either back
down or study machine tools and discover their maximum capacity. This led
him to investigate the matter of cutting speeds. For years he spent all of his
spare time studying this subject, timing machines and experimenting with
different types of cutting tools. He estimated that in the twenty-six years of
his investigation he converted 800,000 pounds of steel into chips. What he
wished to discover was the best depth of cut, the best speed of cutting, and
the best speed at which the tool should be fed into the work. He soon
discovered that, contrary to prevailing opinion, the round-nosed tool was
better than the diamond-pointed tool, that the coarse slow-cutting speed was

better than a fine cut at high speed. He discovered that the best method of
lubricating the tools was to keep them bathed in a heavy stream of water,
supersaturated with carbonate of soda, so as to prevent the metal from
rusting. The best tool steel of that day was known as a self-hardening steel.
Manufacturers of the cutting steels had warned Taylor that he must not use
water on these tools. Taylor, however, was not satisfied to take the word of
others, but proceeded to investigate the matter himself, and discovered that he
could safely increase the cutting speed of his tools 33 per cent by the use of a
heavy stream of water for lubricating purposes. This led Taylor and his
associate, Maunsel White, to investigate the different kinds of tool steels, and
eventually they evolved a chrome tungsten tool which could do from two to
four times the work of other tools. Later vanadium was added to the alloy,
further improving the tool.
At the Exposition in Paris, in 1900, foreign manufacturers were
astonished to find enormous lathes operating at high speed with the cutting
tools taking such heavy cuts and feeding so fast that the nose of the tool was
actually heated to a dull red heat, and yet it kept its cutting edge perfectly.
This was a revelation to tool makers abroad, and it led immediately to the
adoption of American high-speed cutting tools.
The development of the automobile, which began to take on serious
proportions at about that time, is responsible above all other machines for
improvements in American machine tools, and for the extension of the
American system of interchangeable manufacture. When automobiles came
to be made on the interchangeable system and in enormous quantities so that
the cost was reduced to within the limits of the average man’s pocketbook,
they began to make mechanics of men who before that had never used a tool;
and this new and widespread interest in machinery stimulated the production
of better and more efficient tools. Hence the progress of machine tools in the
past few years has been simply phenomenal.

CHAPTER IV

COUNTING SECONDS

Y
OU CAN measure civilization by its timepieces. The higher the
civilization of a community the more it appreciates the value of time
and the more minutely does it measure the passage of time. The
savage divides his day into but two periods: the period of light and
that of darkness; the early Romans divided their day into eight watches, four
watches of daylight and four of night, but the higher and more complex
civilization became, the smaller became the subdivisions of time. People
began to feel the need of carrying the time with them, and about 1500 A. D.
watches came into use, but it was not until 1665 that watches began to be
equipped with minute hands, and it was almost exactly a century later that
they were equipped with a second hand. To-day time means so much to us
that we will fight our way into a subway express, instead of riding more
comfortably in a local train, merely for the sake of saving five minutes. The
tiny second hands of our watches divide the day into eighty-six thousand four
hundred parts, and in some operations we measure time intervals down to the
thousandth part of a second. Only among the most highly civilized nations
are timepieces carried by the common people.
It used to be that time was made for slaves, but now time has made slaves
of us. Shift the hands of the clock and the whole nation is forced to change its
habits.
Time-measuring mechanism is given early prominence in this book
because clocks were among the earliest machines invented, and they furnish
an example of the wonderful ingenuity of inventors before the dawn of the
modern era of machinery. Naturally this chapter must be largely historical.

The first thought of measuring time came from the ancient astronomers
and astrologers, who, in watching the motions of heavenly bodies, the sun by
day and the moon by day and night, found it necessary to keep a record of
these motions and sought about for some mechanical means of doing so. The
studies of the old astrologers were closely associated with religion, and as a
consequence the most advanced intellects were centered upon astronomical
matters and incidentally upon horology. Fortunately the design and
construction of mechanisms for measuring time were not considered beneath
the dignity of the scientists of those early days. Mathematicians felt free to
record their investigations in this branch of mechanics, and as a consequence
of the early cooperation of science and mechanics in this field much real
progress was made, and the development of timepieces was more rapid than
that of any other machine.

TELLING TIME WITH A LEAKY BUCKET

The ancient Egyptians early felt the need of a better clock than the
sundial, because it operated only on cloudless days and was absolutely
worthless to tell off the hours of darkness. Realizing that time is a measure of
motion, they sought for some slowly moving body whose motion could be
used to measure time, and naturally they turned to water. The earliest form of
clock consisted merely of a leaking bucket. Either the bucket was filled with
water which was allowed to escape through a very tiny orifice, or else the
heavily loaded bucket was placed in water and the water was allowed to leak
into the bucket until it sank. The period it took for a bucket to run dry or for a
bucket to fill and sink indicated a lapse of an hour or some other standard of
time.
The idea of subdividing this period was a later development. As the water
leaked out of a bucket, the water level descended, but unfortunately not at a
uniform rate. The weight of water in a full bucket made the drops come faster
than when the bucket was nearly empty. Consequently the time graduations
on the side of the bucket had to be set farther apart at the top of the bucket
than at the bottom. Various ingenious schemes were devised for maintaining
a uniform discharge. In one type of water clock or clepsydra a conical bucket
was used so that there would be a constant relation between the head of water
and the volume in the bucket and the time graduations could be spaced
uniformly.

THE REMARKABLE WATER CLOCK OF CTESIBIUS

The most remarkable clepsydræ were those invented by an old
Alexandrian mathematician, Ctesibius, who lived about 250 years before
Christ. Ctesibius introduced the siphon principle into his clocks, and also
employed gear wheels and even a cord and pulley. Furthermore, he was the
first man to employ jeweled bearings in a timepiece. The use of jewels in
timepieces was reinvented in 1704 A. D. However, Ctesibius used his jewels
in a very different way from that in which they are used now, as will be
described below.

FIG. 25.—THE JEWELED WATER CLOCK BUILT BY
CTESIBIUS ABOUT 250 B. C.

Figure 25 illustrates the most interesting clock he built and it was
arranged to run year in and year out. The clock had a cylindrical face

mounted on a hollow pedestal in which the mechanism was concealed. The
column was divided off into twenty-four hours and a pointer that rose
vertically marked off the lapse of time. But here he was faced with a serious
complication. Hours in those days varied with the time of the year. A day
from sunrise to sunset consisted of twelve hours. In summer, when the days
were long, the hours were long, and in the short days of winter the hours
were correspondingly shortened. To be sure, the variations in the length of the
day are not so great in Egypt as they are in our latitude, because it is nearer to
the equator; nevertheless there is a difference which the precise old
mathematician had to take into account. In order to provide for variations in
the hours, Ctesibius ran the lines spirally around the column and arranged his
cylindrical clockface to turn slightly each day, so that in the winter months
the clock hand or pointer moved over that part of the face where the daylight
hour lines were closer together and the hours of night were farther apart,
while in summer, the reverse would obtain. At the bottom of the column were
two little cherubs. The cherub on the left was a sad little fellow who was
constantly weeping. Tears trickled from his eyes and dropped into a basin.
The tears passed into the hollow pedestal of the clock and gradually filled a
cylinder formed in the base of the clock. A piston in this cylinder supported
the other cherub. As the water gradually filled the cylinder this cherub was
slowly raised and a wand he held in his hand pointed off the hours on the
clockface. When the twenty-fourth hour was reached, a siphon came into
play, which suddenly emptied the cylinder, permitting the pointer to drop.
The siphon discharged its water into a small water wheel, which, by means of
the system of gears, turned the column slightly to bring the hour lines in
proper positions for measuring the time intervals of the next day. The column
made one complete turn in 365 days. The jeweled bearings, referred to above,
were placed in the eyes of the weeping boy, so that the holes that pierced
them would not be enlarged by the constant wear of the water and thereby
increase the rate of flow.

TIMING ANCIENT ORATORS

We have dwelt at considerable length upon this old clock of the pre-
Christian era to show the ingenuity of inventors of that day, and also the
careful study that was made of time by ancient mathematicians and
astronomers. Of course water clocks were used before the time of Ctesibius.
In fact, we read of them in the comedies of Aristophanes, written 400 B. C.

Water clocks were used to limit the long speeches of orators at court, and in
one place we find Demosthenes accusing a man of “talking in my water,”
while at another time, when he was interrupted, he called to the officer to
stop the water, showing that he valued every moment of time allotted to him
for his speech.
In 807 Charlemagne was presented with a clock by the King of Persia.
This consisted of an elaborate mechanism in which were all manner of
wheels, and the clock would actually strike the hours. The driving power,
however, was water.
But there were serious disadvantages in the use of water for the
measurement of time. No great accuracy was ever obtainable with it, owing
to the fact that its volume varied considerably with the temperature, and also
with the dryness or moisture in the surrounding atmosphere. The idea of
using a weight instead of water is claimed to have originated as far back as
990 A. D. The next important advance in the motive power of clocks was in
1500, when Peter Hele of Nuremberg invented the mainspring.
That was long before the pendulum made its appearance. The clock
mechanism was slowed down and kept under control by what was known as
a balance lever. (See Figure 26.) This was a horizontal lever mounted to
oscillate in a horizontal plane. The lever was fitted with sliding weights, so
that it could be carefully adjusted. The last wheel of the train of gears was
provided with escapement teeth, somewhat similar to those used on our
clocks and watches, but which would alternately move the lever this way and
that. The inertia of the lever with the heavy weights on it was sufficient to
prevent the mechanism from racing, and by this means, the motion was
governed and slowed down, so that it measured time with a fair degree of
accuracy.

DISCOVERY OF THE PENDULUM

FIG. 26.—THE BALANCE LEVER, PREDECESSOR OF THE
PENDULUM

The pendulum had an interesting origin. Galileo, while a student in Pisa
in 1581, was attending a service in the cathedral one day when his attention
was drawn to the swinging of a large hanging lamp. One of the attendants had
drawn the lamp toward him, so that he could reach it more readily to light it.
When he let go the lamp began to swing slowly back and forth, and the
observant young student noticed that although the oscillations gradually
slowed down the period of oscillation was constant. He had no watch with
which to measure the length of the period, but being a medical student he
knew that he had a fair timepiece in his own heartbeats, and so by counting
his pulse he proved that it took the lamp just as long to complete each
oscillation when it swept through a long arc as when it died down to but a
few inches. He made note of this peculiar action and began experimenting
with pendulums of different lengths. Then it occurred to him that if he could
time the pendulum with his pulse he could time his pulse with a pendulum.
So he devised a pendulum whose length could be adjusted until its oscillation

would coincide with the throb of a patient’s pulse, and then the length of the
pendulum would give him the rate of the pulse beat. The invention was
seized upon by the medical profession of that day, and the pulsilogia, as it
was called, became an indispensable instrument for physicians.

BUCKET OF A GIANT DREDGE WITH ITS JAWS SPREAD WIDE
OPEN

GOLD DREDGER EATING ITS WAY THROUGH RIVER SANDS

A SUCTION DREDGE EXCAVATING A CHANNEL AND BUILDING
NEW LAND

The idea of using the pendulum to control the action of the clock also
occurred to Galileo, and in later years, after he had lost his sight, he passed
the idea down to his son, Vincent. However, it is generally conceded that the
credit for introducing the pendulum and doing away with the balance lever
belongs to Christian Huygens, the Dutch mathematician, whose first
pendulum clock dates back to 1659.
About the same time Dr. Robert Hooke invented the balance spring which
made it unnecessary to use the pendulum in portable timepieces. Prior to that
watches were fitted with balance levers and they gave a great deal of trouble,
because the time varied with the position in which they were carried. But the
balance wheel overcame all these difficulties and made it possible for a
person to carry an accurate timepiece in his vest pocket, although the early
watches were very bulky mechanisms.

THE FIRST SHIP’S CHRONOMETER

The importance of having accurate timepieces aboard ship was felt as far
back as the time of Columbus. When ships began to go out beyond the sight
of land, it was highly important that they be equipped with some means of
locating their position at sea. By noting the elevation of the sun at noon with
a sextant it was possible to determine the latitude of the ship, but there was
no means of determining its longitude, except by dead reckoning, that is,
using a log to measure the speed of a ship, and estimating its position by
calculating the number of miles it had traveled since leaving port. If ships
could be provided with an accurate timepiece which would keep the same
time as that of some fixed observatory, it would be possible definitely to
locate the position of the ship east or west by noting how fast or slow the sun
was at noon on the particular day on which the observation was taken. This
use of the chronometer is common in these days, but up to 150 years ago
there was no timepiece sufficiently accurate to permit a navigator to tell with
any certainty just where he was.
It was John Harrison, the son of a Yorkshire carpenter, who was the first
to build a chronometer worthy of the name. A prize of 10,000 pounds was
offered by the British Parliament for anyone who could invent and sell a
chronometer which would enable a ship to take a voyage from England to
any of the West Indian islands and back and keep track of the longitude
within one degree. If this could be defined within two-thirds of a degree, the

prize would be 15,000 pounds. Harrison made a bid for this prize, and after
years of effort and patient labor, he succeeded in being granted a trial. His
son, William, was sent on a ship to Jamaica with the now celebrated
chronometer, which was mounted on a large cushion. The instrument was
constantly attended by the young man, its position being adjusted from time
to time to suit the “lie” of the ship. When the ship was eighteen days out, the
vessel was estimated by dead reckoning to be 13° 50′ west of Portsmouth, but
the chronometer indicated the position as 15° 19′. The timepiece was
immediately condemned as worthless, but William Harrison had not lost faith
in the instrument, and insisted that if the ship continued on the same course, a
certain island, if properly marked on the chart, would be seen the following
day. True to the prediction, the next morning at seven o’clock the island
appeared. By means of his chronometer William Harrison was able to predict
the appearance of the other islands, and at the end of the voyage, which
occupied sixty-one days, the chronometer was only nine seconds slow. When
he returned to Portsmouth, after an absence of five months, the error of the
chronometer was only one minute and five seconds, giving an error in
distance of only eighteen miles, whereas thirty miles was the margin of error
allowed by the prize conditions. Such accuracy seemed so incredible that the
chronometer had to be tested on a second voyage, during which it was kept
under lock and key and when William Harrison had to wind the instrument he
was obliged to do so in the presence of two witnesses, lest he move the hand
of the chronometer surreptitiously. At the end of the second voyage there was
no further doubt that Harrison was fully entitled to the prize. Chronometers
soon came to be used extensively, until now they are one of the most perfect
of machines made by man, and operate with an accuracy that is almost
incredible. Usually a ship is provided with several chronometers, so that one
may be used as a check upon another. They are mounted in ball sockets and
gimbal joints, so that they are not affected by the roll of the ship, but always
lie in a horizontal position.

MARVELOUS PRECISION OF MODERN WATCHES

While we may well marvel at the precision of the chronometer, it is
equally marvelous, if not more so, that we may equip ourselves for a few
dollars with a timepiece which is so wonderfully accurate as to vary little
more than a second per day. If one took the pains to regulate his watch
carefully, any of the better makes could be adjusted to such accuracy.

There is nothing very mysterious about the mechanism of a watch. It
consists merely of a train of gears which slow down the motions of the
mainspring to a convenient speed; and these gears moreover keep the proper
relation between the hour and minute and second hands. But when we reflect
that a small watch possesses a tiny second hand which travels something like
ten miles in a year, and that if carefully regulated it will not vary from that of
another watch in the whole journey by more than six or eight inches at the
most, we certainly have a reason to marvel. There are 86,400 seconds in a
day, and a watch is usually arranged to make five beats per second or 432,000
per day. The interval between beats must be adjusted with such minuteness
that one beat must not differ from another by 1/86000 part of a second, else
the watch will register more than a second fast or slow at the end of a day.
And yet watches capable of such precision are being turned out daily by the
thousands. Of course, such perfection would be absolutely impossible
without the use of extremely accurate machine tools. It would have been
impossible as long as we had to depend upon a watchmaker to make a watch
by hand.

THE PACEMAKER OF A WATCH

If we look at the works of a clock the most conspicuous feature is the
rapidly oscillating balance wheel which, by the way, is the most important
part of the watch, for it governs the release of the power stored up in the
spring.
It controls the escapement which brings the whole mechanism of the
clock to a standstill five times each second—in fact it is the pacemaker of the
watch, for it gives the watch a step-by-step movement and fixes the rate at
which the steps are taken.

FIG. 27.—ESCAPEMENT OF A WATCH

The last wheel of the watch train is what is known as an escape wheel. It
is formed with teeth of an odd shape, such as shown at A in Figure 27. These
teeth are engaged by a pair of pallets B and C, carried by a three-armed lever
D. The pallets are usually bits of sapphire or similar hard stone to prevent
wear. The third of the lever is slotted at its extremity to engage a sapphire pin
E, carried by a disk F, which is mounted on the staff of the balance wheel.
The escape wheel A revolves in the direction of the arrow, being impelled by
the mainspring acting through the train of gears. One of the teeth of this
wheel engages the pallet B, causing the lever D to swing on its axis and push
the sapphire pin E toward the left, thereby giving the disk F an impulse in the
same direction. Here a delicate coil spring, known as the hairspring, comes
into play. Without the hairspring the parts would stand still, the escape wheel
being blocked by the pallet B. The hairspring is attached at one end to the
shaft or staff of the disk F and the other to the frame of the watch. It tries to
hold the disk F in a fixed position, but is disturbed by the action of the escape

wheel and is constantly oscillating the disk in its effort to bring it back to its
normal position. When the disk swings over to the left the pallet B is clear of
the teeth of the escape wheel. This releases the escape wheel and it springs
forward in the direction of the arrow, but before it can move through an
interval of one tooth it is arrested by the second pallet C, which has been
projected into its path by the swing of the lever D. The lever swings back
until the pallet C clears the escape wheel and the pallet B engages the next
tooth. And so the action continues, the lever swinging back and forth and at
each complete oscillation releasing one tooth of the escape wheel.
The hairspring takes up the shock of this intermittent motion and a
balance wheel carried by the staff to which F is fastened steadies the
oscillatory motion of the lever D. A watch is full of microscopic parts. In a
small timepiece there are machine-made screws so small that without the aid
of a magnifying glass one cannot see the screw threads cut upon them. But
the most marvelous part of the whole watch is the delicate hairspring and the
means of adjusting its tension and compensating for its expansion and
contraction with changes of temperature.

INANIMATE MATTER IN CONTINUAL MOTION

When working with minute intervals of time many factors must be
considered which are not even thought of in machines of grosser proportions.
It never occurs to the man in the street that not only the animate world but the
inanimate as well is in ceaseless and variable motion. If our eyes were
capable of taking in minute microscopic details, we should see that
everything is expanding or contracting, swelling or shriveling, twisting and
warping in response to the atmospheric changes. Our steel bridges and
skyscrapers are in constant motion; solid concrete dams must be provided
with expansion joints; the Washington Monument goes through a diurnal
gyration in response to the sun’s rays. Of course all this motion is almost
immeasurably small. A bar of steel a mile long will expand ⅖ of an inch for
every increase of a degree Fahrenheit in temperature. The expansion of a
hairspring, which may be nine or ten inches long, is infinitesimally small and
yet this must be considered by the watchmaker. We must remember that the
escapement mechanism divides the day into 432,000 parts, each of which
contains some minute error, for absolute perfection is impossible, and if we
add up all these 432,000 errors they must not foot up to more than a second

per day. If the hairspring expands ever so slightly its power is weakened, but
this loss of power is compensated by an ingenious form of balance wheel.
The rim is in two parts, half of it being attached to one spoke of the wheel
and the other half to the other, as shown in Figure 28. Each half rim is formed
of two strips of metal, an inner strip of steel, and an outer strip of brass fused
together. Brass expands and contracts almost twice as much as steel, and
hence when there is a rise of temperature the rim sections tend to curl in,
bringing their center of gravity nearer the center of the wheel and making less
of a load for the weakened hairspring to move, while on the other hand, when
the spring is contracted by cold, the rims spread out slightly, giving it a
greater load to oscillate. The weight of the balance wheel is thus
automatically adjusted against variations in power of the spring.

FIG. 28.—THE SELF-CORRECTING BALANCE WHEEL OF
A WATCH

Aside from this automatic variable adjustment, the balance wheel must
have a primary permanent adjustment. The rim of the wheel is loaded by
means of small screws. Screws placed near the free ends of the rim sections

will have a greater inward or outward play as the rim contracts and expands,
and by their locations in different positions on the rims the balance wheel
may be adjusted with great accuracy to compensate for temperature variation
in the hairspring.

THE PENDULUM ESCAPEMENT

FIG. 29.—PENDULUM ESCAPEMENT

In the case of clocks such delicacy of adjustment is hardly necessary.
Pendulum clocks, if they are to run accurately, must have their pendulums
automatically adjustable for variations in temperature, because the longer the
pendulum the more slowly it oscillates. Many years ago a grid type of
pendulum was invented in which various alloys were used, which reacted one
against the other and preserved the center of gravity always at the same
distance from the center of oscillation. The action of a pendulum movement
is similar to that of a balance-wheel movement described above. The
pendulum operates a pallet lever similar to that shown in Figure 29. The teeth

of an escape wheel, which are commonly somewhat different from those of
the watch movement, strike the pallets of the pallet lever, and the escape
wheel is intermittently stopped and permitted to proceed. The pressure of the
escapement teeth against the pallets is just enough to keep the pendulum
swinging and the speed of the clock is regulated by lengthening or shortening
the pendulum.
We have added little to clock or watch movements in recent years. About
the only conspicuous modern invention is the torsion pendulum. The
pendulum in this case is a heavy horizontal disk suspended by a wire, and the
disk rotates first in one direction and then in the other, twisting and
untwisting the wire. The advantage of this pendulum is that the oscillations
are very slow, and hence it is possible to keep the clock going for a year at a
single winding.
The electric regulation of clocks is another important improvement. A
clock need not be a very perfect timepiece, but if provided with an electric
regulator its hands are brought up to the correct time every hour in response
to an impulse sent from an accurate master clock which in turn has its time
corrected daily from the National Observatory in Washington.

CHAPTER V

PUTTING RIVERS TO WORK

F
LOWING water exerts a strange fascination upon mankind, even to the
present day. Tourists travel hundreds of miles to view the glorious
spectacle of a riotous tumbling cataract. Is it strange, then, that in the
olden times, when the world was peopled with gods and genii and
strange spirits, the ancients looked upon ceaselessly flowing rivers as the
symbol of life? It was most natural for them to covet the endless power of a
river and eventually, despite their superstitions, to try to utilize some of its
energy.
It may be that sailboats antedate the first water wheel, but it seems much
more probable that flowing water was the first inanimate power harnessed by
man. Windmills were certainly a later development. They possessed the
advantage that they could be located anywhere while the water mill had of
necessity to be built along the bank of a stream. However, the power of the
wind is so unreliable and fluctuates so widely that it was little used, except in
flat countries, where there was little if any available water power.
Water power predominated until the steam engine was introduced, when
it had to give way to an even more reliable power and one which could be
located at any place to which fuel could be transported. Now, however, we
are going back to our first power, seeking it out in the most inaccessible
mountainous regions, because we have discovered the means of taking the
power it yields and transmitting it hundreds of miles, over hills and plains to
the point where we can put it to useful service. Hydroelectric power has very
aptly been termed “white coal.”
The first prime motor was the current wheel, that is, a wheel fitted with
paddles, which was journaled over a stream with the paddles projecting into
the water. This was a very inefficient machine; it converted very little of the
energy of a stream into useful mechanical power. The idea of damming the
stream and letting the waters flow over the dam through a raceway upon a
water wheel was a much later development.

WATER WHEELS

Three types of water wheel which were in universal use before the advent
of the steam engine were the undershot wheel, the overshot wheel, and the
breast wheel (Figure 30). In the undershot wheel the water stored back of a
dam is let out near the bottom of the dam and strikes the under side of the
wheel, so that the top of the wheel turns toward the dam. In the overshot
wheel, the water flows over the wheel striking the paddles or buckets on top
and on the forward side, so that the wheel turns forward. In the breast wheel,
the water strikes the paddles half way up the wheel on the rear side and drives
the wheel in the same direction as that of the undershot wheel.
When we speak of water power we are apt to think of the water as
actually furnishing the energy. As a matter of fact, it is not water but gravity
that drives the wheel, the water being merely the medium that gravity acts
upon. By having the water drop from a great height, its velocity is greatly
increased and the power it imparts to the wheel is much higher. In
mountainous regions it is easy to obtain a high head of water and thus
generate a great deal of power from a relatively small stream. However, the
ancient type of wheel with its paddles or buckets has now practically passed
out of existence, being superseded by the Pelton wheel for high heads and the
turbine for low heads of water.

FIG. 30.—UNDERSHOT, OVERSHOT, AND BREAST WHEELS

INVENTION OF THE PELTON WHEEL

FIG. 31.—SECTIONAL VIEW OF A PAIR OF PELTON WHEEL
BUCKETS SHOWING HOW THE WATER JET IS DIVIDED AND
FOLLOWS THE CONTOUR OF THE BUCKETS

In California, a number of years ago, they made use of what was known
as the hurdy-gurdy wheel. This consisted of an ordinary wheel with bucket-
shaped paddles against which was directed a stream of water at high velocity
through a nozzle. There was a carpenter, named L. A. Pelton, who used to
make a business of building and repairing such wheels and the flumes that
carried the water to them. Although uneducated, he was possessed of
considerable native ingenuity and was a very observant man. One day, when
he was called in to repair a wheel, he noticed that one of the buckets which
had been misplaced received the water from the nozzle without any
splashing. The water struck the edge of the bucket with practically no shock,
whereas the other buckets produced a great deal of splashing. Pelton had
enough knowledge of the principles of mechanics to realize that a splash
means a waste of energy, and that here was a bucket which, although out of
plumb and apparently defective, was really more efficient than any of the
others in the wheel. It occurred to him then that instead of having the jet of
water strike the middle of the buckets it ought to strike the edge, so that all its
power would be absorbed without any wasteful splashing. He might have
displaced the jet laterally so as to accomplish this result, but he realized that

that would have produced a considerable side thrust on the wheel, which, of
course, would have been objectionable, and so he hit upon the plan of using
double buckets and letting the stream of water strike the pair of buckets along
their dividing line. (See Figure 31.) This would split the stream in two and let
each half strike the slanting face of the bucket, and follow the surface around
in the same way that it did on the single misplaced bucket, but the reaction or
side thrust on one bucket would be counteracted by that on the other. This
idea proved successful and out of it has grown the Pelton wheel which is now
universally used in all power plants employing high heads of water.

A 4,000-FOOT HEAD OF WATER

A notable illustration of such a plant is the great installation at Big Creek,
Cal. Big Creek, despite its name, used to be a small stream flowing down the
mountains into a canyon. One would hardly suppose that it was capable of
yielding much power, but it had its source high up in the Sierras and was fed
mainly by melting snows. In the springtime, it swelled to a good-sized
torrent. By building three dams near the top of the mountain, a lake was
formed in which the water of the melting snow was impounded, so that a
steady stream of water could be supplied the year round for power purposes.
But even so, the stream hardly amounts to very much if we consider only the
quantity of water that passes through it. The particular advantage of this
installation is the fact that in a distance of six miles from the dam the creek
falls 4,000 feet.
An inhabitant of the Eastern States who is unused to mountain heights
may gain some conception of the meaning of this elevation by gazing up to
the pinnacle of the Woolworth Tower, which rises 795 feet above street level,
then mentally multiplying its altitude by five. Evidently even a small stream
of water dropping from such an elevation would develop an enormous
amount of power. In fact, it was considered inexpedient to use the entire fall
at a single drop and so it was divided into two stages. The water is carried
through a tunnel three-quarters of a mile long and then through a flow pipe
along the face of the mountain to a point where it may drop 2,000 feet to the
first power plant. After passing through this plant the water is discharged into
the creek and is then diverted into a second tunnel four miles long and a
series of steel conduits to a point from which it may drop 2,000 feet more to
the second power plant. In each power house there are two electric

generators, each fitted with a pair of Pelton wheels. These wheels are a little
less than eight feet in diameter and each one develops 23,000 horsepower.
The water is directed into the buckets of the Pelton wheel in a stream six
inches in diameter, and it issues from the nozzle with a velocity of 300 feet
per second or about 210 miles per hour. A jet of water is almost like a solid
bar of wood. In fact, it is impossible to chop through it with an ax. The water
would swing the ax out of one’s hand before it got part way through the jet.
Traveling at such a high speed the friction is so great that it would tear the
skin off one’s hands, if it did not actually tear the hand off the arm, and yet it
strikes the buckets of the wheels with no shock at all, for the first part of the
bucket it touches is nearly parallel to the jet, and as the water sweeps around
the curved face of the bucket it loses practically all of its pressure and
velocity and falls into the tail race. The electric power generated by the two
plants is stepped up to 150,000 volts and sent out over transmission lines to
points of service. The street cars of Los Angeles are connected by a 240-mile
electric harness to the hydraulic horses of Big Creek.
Powerful as this stream is, a still higher head is used in Switzerland, at
Lake Fully, where there is a drop of over a mile in a distance of 2.8 miles.
The water is carried by a short tunnel through the mountain, and then makes a
drop of over 5,000 feet to the power plant, where it strikes the Pelton wheels
at a velocity of 400 miles per hour, or about seven times the speed of a fast
express train.

HARNESSING THE MISSISSIPPI

In contrast to such high heads, we have the low-head power plants which
are employed where a large volume of water is available. The most notable
installation of this type, and the largest in the world, is that at Keokuk, Iowa,
where a dam has been thrown across the Mississippi River. For many years it
was thought impossible to make any use of the vast volume of water that
flows through this great river. But above Keokuk there used to be a rapid
extending back about twelve miles. By building a dam across the river just
below the rapid it was possible to obtain a working head of about thirty-two
feet, and with the enormous volume of water available this provided
sufficient energy to make the development worth while. In marked contrast to
the installation at Big Creek, it is volume rather than velocity that is
employed, and hence turbines rather than Pelton wheels are used. More water

goes through a single turbine than is used in the whole of the city of New
York with all its elaborate aqueduct system. Enormous turbines are used,
fifteen feet in diameter, and when the installation is complete there will be
thirty units, each yielding 10,000 horsepower, or a total of 300,000
horsepower. A turbine, it may be explained, differs from the ordinary water
wheel in the fact that the water runs through the wheel instead of around it
(Figure 32). The water may enter at the center and then flow out at the
periphery, or it may enter at the periphery and then be discharged from the
center of the wheel, or it may run axially through the wheel. In a Pelton
wheel there is a single jet which strikes but one pair of buckets at a time, but
in a turbine there are many jets distributed all around the circumference of the
wheel. The water is divided into a series of jets by being forced through a
stationary set of curved vanes. The blades of the rotor or revolving part of the
turbine are oppositely curved. If the rotor were immovable the jets would
have to change their direction in passing through the rotor, but as the rotor is
free to turn, the jets react against these blades and set the wheel to revolving.
The turbine may be designed to run either on a horizontal axis or on a vertical
one.

FIG. 32.—TURBINE WHEELS; INFLOW TYPE SHOWN ON THE
LEFT AND OUTFLOW TYPE ON THE RIGHT

The turbines used at the Keokuk plant are of the inflow type. The rotor is
mounted on a vertical shaft in a scroll-shaped concrete chamber, something
like a snail shell. Water pouring into this chamber is thus given a swirling
motion in the direction of rotation of the wheel. As it flows into the wheel it
passes first through a ring of fixed vanes, which divide it into the jets.
The highest velocity of a wheel is naturally at the periphery and the
advantage of an inflowing turbine such as this is that the water is traveling at

its highest velocity when it strikes the periphery of the rotor. As it loses its
velocity it flows in toward the slower-moving portions of the rotor. Finally it
reaches the center, after giving up practically all its energy, and falls into the
tail pool through a draft tube at the center of the rotor.
The scroll chambers at Keokuk are thirty-nine feet in diameter and the
draft tubes are eighteen feet in diameter. Water enters the scroll chambers
with a velocity of fourteen feet per second and comes out of the draft tubes
into the tail pool with its velocity cut down to but four feet per second.
Compare this with the velocity of the water jets at Big Creek!
The current generated at Keokuk goes to St. Louis and surrounding towns
and serves a population of 1,120,000.
Now that we have learned how to transmit electrical power without
serious loss over enormous distances, it is only a question of time before all
the water power in the world is harnessed and put to the service of man. The
power costs nothing after once the plant has been built; the only expense is
that of maintaining the machinery and keeping it in repair. It is estimated that
there is some 200,000,000 horsepower available in this country, but this
includes all flowing water, much of which it would be impracticable, if not
almost impossible, to utilize. However, there is about 60,000,000 horsepower
commercially available, according to the figures of the U. S. Geological
Survey, of which we have developed so far only 6,000,000 horsepower.
The ancients used flowing streams not so much for power purposes as to
lift water to a higher level so that it would flow into their irrigating ditches.
Nowadays, electricity, steam, or air is used for elevating water, but we have a
very ingenious machine which makes the stream lift a part of itself. This
machine is very different in principle from the old Egyptian noria. It depends
upon the kinetic energy of water in motion. You cannot push a nail into a
piece of wood with a hammer but you can easily drive it in by striking it with
the hammer. As the hammer is swung it acquires what we term kinetic energy
or energy of motion.

SETTING KITCHEN FAUCETS TO WORK

It is not generally realized that water in motion also acquires kinetic
energy. Whenever a faucet is turned off very quickly, there is a hammering
sound which is due to the fact that the moving water in the water pipe is
brought to an abrupt stop. This puts a severe strain on the piping. A great deal

of trouble was experienced from this source in the early days of plumbing. At
a hospital in Bristol, England, there was a lead pipe leading from a cistern in
one of the upper stories to the kitchen. Every time the faucets were turned off
abruptly the momentum of the water caused the lead pipe to expand, and
every now and then the pipe was burst. In order to relieve the situation, a
plumber connected a pipe to the faucet and carried it up the side of the
building to the level of the cistern. His idea was that whenever the water was
turned off suddenly it would have a vent leading up to the level of the water
reservoir. Much to his surprise, the water issued from the pipe in a jet of
considerable height. To prevent the escape of the water, he extended the pipe
considerably, and still a jet of water would issue from it. Eventually the relief
pipe was carried up twice the height of the cistern and even then the water
would squirt out occasionally when the faucets in the kitchen were turned off
very suddenly. Then the idea was conceived of placing a reservoir on one of
the upper floors of the hospital and letting the jet of water fill this reservoir.
Every time the faucet was operated in the kitchen a certain amount of water
flowed into the new cistern, and in this way it was kept supplied with enough
water to furnish that which was required for the upper floors of the hospital.

FIG. 33.—SECTIONAL VIEW OF A WATER RAM

It is on this principle that the hydraulic ram operates. Water from a stream
is made to flow down a pipe, and as it gains velocity a check valve suddenly

stops the flow which produces enough pressure to force open a valve in an air
chamber and let some of the water enter the chamber. As soon as the pressure
is relieved the check valve opens and the valve into the chamber closes
automatically until a moment later the stream of water has gained sufficient
velocity to repeat the performance. Thus an intermittent jet of water is forced
into the air chamber and thence through a pipe to a reservoir. The height to
which the water will rise depends entirely upon the velocity of the water
flowing through the system. The air chamber is necessary to cushion the
action of the hydraulic ram and provide a fairly steady pressure upon the
water that flows up through the vent pipe. The check valve is entirely
automatic. It is held open against the pressure of the water by a spring or a
weight, but when the water is in motion is dragged shut, only to spring open
again when the pressure is reduced by the escape of the water into the air
chamber.

FIG. 34.—THE GYRATING WATER METER

There is a very ingenious water-driven motor which is employed merely
to record the amount of water flowing through it. This is the Thomson water
meter which is illustrated in Figure 34. It consists of a circular chamber with
inwardly dished or conical top and bottom walls. In the chamber is a flat disk
with a ball and socket bearing. At one side there is a vertical diaphragm in the
chamber which passes through a slot in the disk. This prevents the disk from

revolving, but it is free to oscillate. It has a motion similar to the gyrations of
a top when it is beginning to lose speed and die down, except that the disk
does not revolve. When the disk is in contact with the bottom wall of the
chamber on one side it contacts with the top wall on the other so that the
chamber is virtually divided into two compartments by the disk, but by
gyrating the disk these compartments are made to revolve. Water enters at
one side and discharges at the other side of the vertical diaphragm. Now, if
the disk is in the position shown in Figure 34, the water, on entering, bears
upon the upper face of the inclined disk and wedges its way between the disk
and the upper wall of the chamber, making the disk oscillate on its ball center.
As the edge of the disk rises across the face of inlet port the water entering
the chamber bears against the under side of the disk, continuing the gyratory
motion. The water cut off on the upper side of the disk is carried around to
the outlet and discharges, while a fresh supply flows in on the other side of
the vertical partition and at the next half turn the water in the lower
compartment discharges at the outlet side of the partition, while the
compartment is filling on the other side of the partition. A measured amount
of water flows through the chamber at each gyratory oscillation of the disk. A
train of gearing is driven by the gyrating disk which operates a set of dial
pointers and a measure of the amount of water passing through the meter is
indicated.

DIGGING WITH WATER JETS

We have referred to the enormous velocity of the jets used to drive Pelton
wheels. Where high heads of water are obtainable water jets are used very
effectively for excavating purposes, particularly in mining plants for washing
down gold-bearing gravel banks. If water is not found near such banks
expensive canals, flumes, and pipe lines are constructed and even tunnels are
bored to bring the water to the point where it can be utilized. Some of the
giant nozzles spout streams from 2 to 8 inches in diameter with a pressure of
from 50 to 200 pounds per square inch. The powerful streams tear into the
gravel banks, washing them away into sluices in which riffle boxes are placed
to catch the precious metal. The back pressure of these nozzles is very heavy
and the larger ones have to be provided with strong anchorages. Water in
motion resists any change of direction and long levers have to be provided to
permit the miners to guide the nozzles.

The hydraulic jet is also used for general excavating wherever water
power is available. Sometimes it is employed under water when clearing a
channel to level down piles of stones that are too large to be picked up by a
suction dredge. Hollow iron piles are driven into a sandy bottom by means of
hydraulic jets. No hammer is needed. Water is pumped into the pile and on
issuing from the bottom of the pile it carries sand with it, making a hole into
which the pile sinks. Wooden piles are driven in the same way by loosely
attaching a water pipe to them so that the pipe may be withdrawn when the
pile has been driven far enough. The pile is grooved at the lower end so that
the pipe outlet may be centered at the bottom of the pile.

COMPRESSING AIR WITH WATER

FIG. 35.—HOW THE VENA CONTRACTA RAISES WATER

A very ingenious apparatus for compressing air was invented in the
earliest years of the iron age to furnish a continuous blast of air for the
Catalan forges. This compressor, known as a “trompe,” can hardly be termed
a machine because it contains no moving parts except water, which is the
motive power, and the air which it traps and compresses. To understand its

operation we must look into a peculiar property of water flowing out of a
reservoir into a pipe or nozzle. There is a converging motion that tends to
contract the jet of water just after it leaves the pipe. This is known as the vena
contracta. It produces a partial vacuum in the pipe. If air ports are opened
into the pipe at this point, air will be sucked in to fill the vacuum and will be
carried out of the pipe by the friction of the water. In Figure 35 a pipe is
shown running from the vena contracta to a water tank below. The rise of
water in this pipe indicates the degree of vacuum produced by the jet.

FIG. 36.—THE “TROMPE” BY WHICH COMPRESSED AIR
WAS FURNISHED FOR CATALAN FORGES

This principle is used in the hydraulic-air compressor or “trompe” as it is
called. Water flows out of one reservoir through a pipe into another reservoir
lower down. (See Figure 36.) Air enters the pipe through ports at the point
where the vein of water contracts and is carried down into the second
reservoir. This reservoir is sealed so that the air is trapped in it. The water
passes out through a pipe which is carried high enough to keep a certain
pressure of air in the reservoir and prevent it from blowing out.

FIG. 37.—DIAGRAMMATIC SECTION OF A LARGE HYDRAULIC
AIR COMPRESSOR IN MICHIGAN

There is a compressor of this type, constructed on an enormous scale, in
the northern part of Michigan. A sketch of the compressor is given in Figure
37. The air reservoir in this case is a huge underground rock-walled chamber
nearly 350 feet below the surface, 8 feet wide, 26 feet high, and about 280
feet long. There are three intake pipes, 5 feet in diameter, each filled with an
annular funnel-shaped head, which sucks air into the water and carries it
down into the chamber. At the bottom of each intake pipe there is a concrete
block with a conical top projecting up into the pipe. The column of water
flowing down the pipe is spread out into an annular stream by the conical
block and the bubbles of air escape into the chamber. The water outlet of the
chamber is an inclined shaft which leads up about 270 feet to the surface of
the ground where it discharges into the tail race. The water is forced up this
inclined shaft by the pressure of the air trapped in the chamber. The mouth of
the shaft is, of course, below the level of the water in the chamber so that
there is no chance for the air to escape unless the pressure becomes
excessively high, when it will force the water level below the mouth of the
shaft and blow out. The discharge sometimes forms a geyser 700 feet high.
The air will continue to blow until the pressure is reduced enough for the
water level to rise and cut off access of the air to the mouth of the shaft.
Under normal conditions there is a fall of 343 feet from the water level at the
top of the intake pipe to the water level in the chamber, and a vertical rise of

271 feet from the water level in the chamber to the tail-water level. The
difference, or 72 feet, represents the working head. With all three intakes
operating, a total of 5,000 horsepower is developed. Each intake delivers
11,930 cubic feet of air per minute at a pressure of 128 pounds. Air enters the
intake heads through tubes ⅜ inch in diameter and there are 1,800 of them to
each head. The air is employed to operate machinery and tools in an adjacent
mine.
One advantage of this type of air compressor is that it cools the air while
compressing it. This was hardly an advantage in the Catalan forges, but when
the air is used to drive machinery it is important that it be precooled. When
air is compressed by mechanical means a great deal of heat is generated and
the machines must be water jacketed to extract this heat, but in the hydraulic
compressor the air bubbles are compressed as they pass down with the water
to the reservoir and the water absorbs the heat, delivering cool compressed air
at the bottom of the intake pipe.

CHAPTER VI

LIQUID LEVERS AND GEARS

M
ANY an inventor has strayed off into the delusive pursuit of
perpetual motion because he did not know that the pressure in a
body of water at any given point is equal in all directions, upward,
downward, or laterally.
A cubic foot of water weighs 62½ pounds. Take a hollow column with
an internal cross-sectional area of one square foot and if it be filled with
water to a depth of ten feet there will be a weight of 625 pounds of water in
the column and hence a pressure of 625 on the bottom of the tube or 4.34
pounds on every square inch of the bottom. But the water presses on the
sides of the tube as well and the amount of this pressure depends upon the
depth or “head” of water and not upon the quantity of water. At the bottom
of the tube the pressure on the side walls is 625 pounds per square foot or
4.34 pounds per square inch; at a depth of one foot the pressure on the side
walls is 62.5 pounds per square foot or .434 pound per square inch; at a
depth of two feet it will be .864 pound per square inch, etc. The pressure on
each square inch depends not upon the mass of the water but upon its depth.
If the column of water had a cross-sectional area of a mile or a thousand
miles, the pressure at a depth of one foot would always be .434 pound per
square inch. (Of course there are slight variations from this figure due to
salt or other substances dissolved in water or to changes in density
produced by variations of temperature, but we need not consider such
minute differences here.) That is why a dam which is strong enough to hold
back the waters of a pond will be just as able to hold back the waters of the
whole ocean if it be placed in a sheltered bay where ocean waves cannot

tear it to pieces. The ocean, despite its enormous mass, can exert no more
pressure per foot of depth than the water in a cistern.

WHY A SHIP FLOATS

It is because the pressure of water at a given depth is exerted upward, as
well as laterally and downward, that a ship floats. It is the upward pressure
of the water that holds up the boat. When an object is placed in a reservoir
of water it sinks into zones of increasing pressure until it finally reaches a
depth at which the pressure on the bottom of the object balances the weight
of the body. If the body is entirely submerged before reaching such a point,
it will continue to sink to the bottom of the reservoir because water will
flow over the top of the object and keep adding downward pressure to offset
the increasing upward pressure. The amount of water in the reservoir makes
no difference. A battleship will float just as high in a flooded dry dock as it
will in the open ocean. If the dry dock were so narrow as to leave a
clearance of but a few inches of water around the ship, the latter would still
float even though the ship weighed considerably more than the water in the
dock.
There is a big difference, then, between the weight of water and the
pressure it exerts. In Figure 38 we have an L-shaped receptacle with the
lower arm of the L terminating in a chamber A. The top wall B of this
chamber measures ten square inches. The tube C has a cross sectional area
of one square inch. If tube C is filled to a height of twelve inches above
wall B we shall have an upward pressure of 0.434 pound on every square
inch of wall B, or a total of 4.34 pounds. If by means of a plunger D we add
a hundred pounds of pressure to the column of water in tube C, we shall be
adding a thousand pounds to the pressure on the wall B. The side walls and
bottom of the chamber A will also be subjected to a pressure of 1,000
pounds per inch plus the pressure due to the depth or head of water.

FIG. 38.—DIAGRAM
ILLUSTRATING HYDROSTATIC
PRESSURE

THE AIR-LOCK OF A PNEUMATIC CAISSON

SUBAQUEOUS TUNNEL, SHOWING THE SHIELD IN THE
BACKGROUND

FIG. 39.—PRINCIPLE OF THE HYDRAULIC PRESS

Here, then, we have a convenient means of multiplying force or effort
and it is a means that is used very largely in certain classes of machinery.
Figure 39 is a diagrammatic representation of a hydraulic press. It consists
of a cylinder A in which is fitted a ram B. An L-shaped tube C connects
with the cylinder and is fitted with a plunger D. The cylinder and tube are
filled with water and then when the plunger is depressed the ram B has to
rise, If the area of the plunger is one square inch and that of the ram thirty
square inches, a 100 pounds pressure on the plunger will exert 3,000
pounds of lift on the ram.

HYDRAULIC LEVERAGE

However, we must remember that in mechanics, as in all walks of life,
we cannot get “something for nothing.” If we multiply the pressure or force,
we must pay for it in some way, otherwise we should be getting more work
out of the press than we put in it, which is what the perpetual motion crank
is ever trying to do. As the cross-sectional area of the plunger D is only
1/30th of that of the ram, the plunger must descend thirty inches to raise the
ram one inch. We need not consider the difference in the head of water
because it would not amount to more than a few ounces at most, nor need
we consider frictional losses. The case is parallel to that of the lever. In fact,
we may consider the hydraulic press as a fluid lever with the water in tube
C as the effort arm and that in cylinder A as the weight arm. The two arms

are here so proportioned that the power arm must move thirty times as far
as the weight arm. The work put into the press is exactly balanced by that
we get out of it. An effort of 100 pounds exerted through a distance of thirty
inches is exactly balanced by the moving of 3,000 pounds through a
distance of one inch.
It is a decided disadvantage to have to move the plunger so far and in
actual commercial practice hand-operated hydraulic presses are not worked
in that way. A pump is used to force water into the cylinder so that a great
many short strokes may be taken in place of one long one, and the pump
handle provides an added leverage, enabling a man with little effort to exert
an enormous lift. The water enters the ram cylinder through a valve, and the
pressure is maintained on the ram until relieved by the opening of an outlet
port.

MAUDSLEY’S LEATHER COLLAR

All this seems very simple and one would suppose that the inventor of
the hydraulic press must have been exceptionally free from the troubles and
trials that beset most inventors. However, there is a vast difference between
a laboratory apparatus and a commercial machine. When, towards the close
of the eighteenth century, Joseph Bramah, the eminent British tool builder,
invented the hydraulic press, he experienced all sorts of difficulty in holding
the water in the ram cylinder. Of course, the ram has to slide freely into and
out of the cylinder, but how could he prevent the water from leaking out
past the ram? He resorted to all the plumbing expedients of the day. He used
a stuffing box and gland, but when this was packed tight enough to hold the
water in, it gripped the ram so tightly that the latter would not move down
into the cylinder on the return stroke. Bramah had in his employ a very
clever young mechanic named Henry Maudsley, who later became famous
as an inventor and designer of machine tools. We read of him in Chapter III.
Maudsley attacked the baffling problem of the hydraulic press and provided
a solution that survives to this day. In place of the stuffing box which is a
means of jamming a mass of cotton waste about the collar, he provided a
cupped leather collar. When the pressure was applied it expanded the collar
and made it bear tightly against the ram, but on relieving the hydraulic
pressure the pressure of the cup leather was also reduced automatically.

There are many machines analogous to the hydraulic press in principle.
They do not use water in every case for the fluid lever. Where the fluid is
used over and over again oil is frequently employed. The compactness of
this form of lever makes it most useful wherever an operation calls for the
overcoming of a very heavy load or resistance through a relatively short
distance. For instance, there are machines for bending pipe, for curving
railroad rails, for punching holes in metal, for pulling wheels off their
shafts, for jacking up heavy weights, for baling cotton, paper, and other
materials, all of which operate on the same principle as the hydraulic press.
Water pressure is supplied sometimes by a hand pump, sometimes by a
power-driven pump, and sometimes it is taken from a reservoir in which
compressed air imparts the requisite pressure to the water.

BLASTING WITH WATER

A novel use of water pressure has been developed in England. In certain
mines it is dangerous to use dynamite for blasting purposes owing to the
presence of explosive gases, and successful experiments have been made
with hydraulic cartridges. This consists of a cylinder of steel fitted with a
series of little plungers arranged in a row in the cylindrical wall of the
cartridge. As in powder blasting, a series of holes are drilled in the face of
the rock and the cartridges with the plungers retracted are fitted into the
holes. Then the cartridges are connected to a high-pressure water supply.
The water forces the plungers out, exerting enough pressure to burst the
rock. Not only is this system perfectly safe, but it is economical, because
the gallery does not have to be cleared of workmen before every blast.
There is more certainty in the use of water cartridges, and the danger,
common where dynamite is used, of having the rock drill or pick strike and
explode a stick of dynamite which failed to go off with the rest of the
charge in a previous blast is avoided.
Hydraulic pressure is also used in jacks for lifting heavy weights. The
principle of the hydraulic jack is the same as that of the hydraulic press.

RAISING A BRIDGE SPAN WITH WATER

An interesting illustration of the use of these liquid levers was afforded
in the construction of the Quebec Bridge. This huge bridge, it will be

recalled, consists of two cantilevers which stretch out from opposite shores
of the St. Lawrence River and support between them a center span 640 feet
long and weighing 5,400 tons. The span was built on barges, towed down to
position between the cantilever arms and then lifted up 150 feet to the floor
level of the bridge. Eight 1,000-ton hydraulic lifting jacks were used, two at
each corner of the span. They were ideally suited to this kind of work. The
bridge span had to be lifted with utmost care and the motion had to be
simultaneous on all four corners. If one corner were raised faster than
another the span would be twisted and subjected to serious strains. In the
first attempt the fastening gave way at one corner and the span crumpled up
and plunged down into the river. But a year later at the second attempt the
span was hoisted successfully to position. The jacks had a lift of two feet,
and, counting the time required to secure the huge plate chains by which the
span was suspended, move the jacks down and give them a fresh hold, it
took fourteen minutes to complete each two-foot lift. The work was done
only during the daylight hours and on the third day the span was finally
brought into position and made fast to the cantilever arms by means of
twelve-inch pins driven home at each corner.
Hydraulic power is used very largely in the operation of cranes. As the
plunger or ram has a very limited range of motion some means of
multiplying distance of travel is required. One simple scheme is to use a set
of pulley wheels or sheaves attached to the cylinder and another set to the
ram and pass the hoisting chain around them. If we refer back to Figure 16,
on page 34, we shall see that seven feet of rope must be pulled in at E in
order to raise the lower pulley block one foot. It is very evident that the
process can be reversed. Power might be applied to spread the two-pulley
blocks apart when a movement of one foot would produce a travel of seven
feet at E. That is what is done on the hydraulic crane. The ram is lifted,
spreading the pulley blocks apart and thus multiplying the motion of the
lifting cable to any extent, depending upon the number of sheaves, so that a
travel of but a few feet will result in lifting a load forty or fifty feet.

HYDRAULIC ELEVATORS

The same principle is used in hydraulic elevators. The hydraulic
cylinder lies horizontally on the basement floor and by means of pulley

gearing a short motion of the plunger is sufficient to raise the car several
stories.
In a more modern type of elevator the plunger acts directly on the car.
The plunger is long enough to reach to the top story of the building which
means that it must sink far into the ground in order to let the car down to the
first story or basement. A steel pipe is sunk into the ground and serves as
the cylinder and in this the long plunger operates. In one of New York’s tall
buildings the cars are lifted to a height of 282 feet. The plungers are 6½
inches in diameter and they travel at a speed of over 400 feet per minute.
The car which, when loaded, weighs 1,617 pounds, is supported on the top
of the plunger. However, counterweights are provided which balance the
weight of the car, so that practically the only weight lifted by the plunger is
that of the passengers. The advantage of this type of elevator is that it
reduces the danger of accident. The motion of the car is steady and easily
controlled. The car cannot move down above a given speed and the only
possible danger is that the plunger might break. However, a shaft of steel
6½ inches in diameter, even if hollow, is hardly likely to give way even
under the most extraordinary loads to which it might be subjected in
elevator service.

LIFT LOCKS FOR CANALS

There is another type of elevator that completely dwarfs anything used
in office buildings. On some canals where it is necessary to make a sudden
change of level of considerable extent, instead of using a flight of locks, a
hydraulic elevator is employed to lift or lower not only the vessel but the
water it is floated in. There are two huge tanks which ply between the upper
and lower levels of the canal. These are so connected that as one rises the
other descends. The tanks are big enough to take in the largest vessels that
are likely to use the canal. They are fitted with water-tight gates at each end,
and after a vessel has entered one of them, say at the lower level, the gate
behind it is closed. Then hydraulic mechanism is operated to lift the tank,
and when the top is reached the other gate is opened and the vessel sails out
into the upper level. It seems like a tremendous undertaking to lift a heavy
ship, but the two tanks balance each other and the only work that has to be
done is to overcome the friction and inertia. No matter how heavy a vessel
may be, it will not disturb the balance between the two tanks. Nor is it

necessary to have a ship in each tank, for the same depth of water is
maintained in the two tanks, and when a ship enters the weight of the tank
is not increased, for the ship displaces its own weight of water.

HYDRAULIC VARIABLE SPEED GEAR

Water is frequently used to take the place of toothed gearing for the
transmission of power, particularly where it is desirable to vary speed. One
of the disadvantages of toothed gearing is that a change of speed can only
be made by shifting gears. The speed cannot be varied gradually but is
changed by abrupt steps. The guns of a battleship must be kept trained on
the target, while the ship rolls in the waves under them, so as to be ready for
a broadside at any instant. A telescope is secured to the barrel of the gun
and a man known as a “pointer” tries to keep the cross-hairs of a telescope
on the target by constantly elevating or depressing the gun. The speed of the
elevating machinery must be constantly changing; now running at high
speed, the next instant barely moving, and the next moment reversing.
To produce these variations a hydraulic variable speed gear is used. The
construction is somewhat complicated, but the general principle of
operation is simple. In a common pump water is lifted by operating a
plunger in and out of a cylinder. It will be readily understood that the
operation may be reversed, and if power is applied to the water to force it
through the pump, it will make the plungers move in and out of the
cylinder. In the hydraulic variable speed gear the driving shaft is made to
operate a set of little pumps which are connected to a second series of
pumps that act upon the driven shaft. Instead of water oil is used, and the oil
pumped by the driving pumps is forced into the driven pumps. The latter
pumps are so connected to the driven shaft as to cause it to rotate. But by a
simple mechanical expedient the stroke of the driving pumps can be varied
at will from maximum to zero, and the motion of the pumps can also be
reversed. The variable amount of oil pumped into the driven pumps varies
the speed of the driven shaft, for if it takes two strokes of a driving pump to
fill the cylinder of a driven pump the driven shaft will travel at only half the
speed of the driving shaft.
In turbine-driven vessels some sort of gearing is required between the
propeller and the turbine. In order to operate at its best efficiency a turbine
must run at very high speed, but this speed is entirely too high for the

propeller. There is a limit to the rate at which a propeller may be driven. If
this limit is exceeded, the propeller merely bores a hole in the water,
forming a vacuum which produces a drag on the ship. It is customary to
interpose some form of gearing between the propeller and the turbine shaft,
but because of the high speed and the vast amount of power to be
transmitted it is a difficult matter to design gearing that will be reliable.
Furthermore, it is desirable to vary the speed of the vessel and even to
reverse it without slowing down the turbine engine. In some cases a
specially designed system of toothed gearing has been employed, in another
the power of the turbine is converted into electricity and then reconverted
into mechanical power by means of a motor on the propeller shaft. This
provides a very efficient transmission, because the electricity can be very
conveniently controlled to accelerate, retard, or reverse the speed of the
propeller motor. The same thing can also be done by using a hydraulic
transmission gear. This, although quite different from the variable-speed
gear, yet operates on the same general principle. The turbine drives a
centrifugal pump and the water thus pumped is fed to a horizontal water
turbine on the propeller shaft. By an ingenious arrangement of turbine
wheels the speed of the propeller shaft may be varied at will.
Hydraulic machinery is notable for its reliability. Sometimes water or
oil is used as a convenient means of transmitting pressure from one part of a
machine to another. If we take a tube filled with water and fit a plunger in
each end, then, when one plunger is depressed or pushed in, the other will
be expressed or pushed out. The pipe may be twisted around in any
direction or be tied up in a double bowknot, and yet pressure applied to one
cylinder will immediately be felt by the other. This method of transmission
may do away with a vast number of gears or levers.
Water is comparatively incompressible and hence not a very adaptable
means of transmitting power, but a certain amount of flexibility is secured
in some systems by the use of what is termed an “accumulator.” This
consists of a large cylinder fitted with a plunger. The plunger is heavily
weighted and it maintains a constant pressure upon the column of water in
the cylinder. If, for instance, a hydraulic crane is being used and suddenly a
larger quantity of water is required than would normally be delivered by a
pump, it is automatically supplied from the cylinder of the accumulator, and
at a constant pressure. The accumulator is arranged to control the throttle
valve of the steam pumping engine so that when the plunger of the

accumulator reaches a predetermined height the stream is cut off and the
engine stops pumping.

TRANSMITTING POWER WITH SOUND WAVES

During the war a new use of water for power transmission was
discovered and it is now being developed for the operation of mining
machinery. The inventor of the new transmission is George Constantinesco,
a Rumanian engineer. His first application of the invention was to a
mechanism for synchronizing the firing of a machine gun with the rotation
of an airplane propeller, so that it was possible to fire through the propeller
without danger of striking its blades. There were several existing methods
of gearing the propeller to the machine gun, but Constantinesco’s system
proved so much more reliable that it was adopted and widely used by the
British in their battle planes.
Instead of gears and levers, the Rumanian engineer used a column of
water in a heavy steel tube to conduct impulses from the propeller to the
machine gun. The pulsations produced by the propeller were too rapid to
cause an actual displacement of the whole column of water in the tube, but
a wave of pressure traveled through the water column at an enormously
high velocity.
We are wont to think of liquids as incompressible, but they are actually
slightly compressible and highly elastic. This is demonstrated by the
submarine telephone or the submarine bell. Water, we know, is an excellent
medium for the transmission of sound, but sound, we know, is produced by
a succession of pressure waves. If water were absolutely incompressible, it
could not convey sound from one point to another. When sound travels
through a speaking tube the whole column of air does not move back and
forth simultaneously, but it is divided into a series of waves. Each particle
of air has a local oscillatory motion which it communicates to its neighbor,
producing alternate compression and rarefication, and it is this wave action
that travels through the column. The same is true of water, except that the
rate of travel of the pressure wave in water is much higher than in air,
namely 4,800 feet per second. It is this wave transmission that
Constantinesco employed and which he calls “sonic” wave transmission.

To-day sonic wave transmission is used to operate rock drills. A wave
generator is used, which acts somewhat on the principle of a pump. A pair
of plungers are reciprocated at a rate of forty strokes per second by means
of an electric or gasoline motor, and they produce a train of pressure waves
in a column of water. The water is contained in a specially designed flexible
steel piping which runs to the rock drill. The pressure waves operate a
plunger in the drill and the plunger carries the drill steel. The latter pounds
the rock under the wave impulses at the rate of forty strokes per second.
Sonic wave transmission is analogous to alternating current
transmission of electricity. There are direct equivalents in the wave
transmission, of volts, amperes, frequency, angle of phase, induction,
inductance, capacity, resistance, condensers, transformers, and single-phase
or polyphase systems.

CHAPTER VII

AIR VS. WATER

T
HE STEAM engine had its origin in a kitchen; the modern clock was
first conceived in a cathedral; our laws of motion were discovered
under an apple tree, but, strangest of all, pneumatic engineering had its
beginning in a barber shop. In each case it was an inquisitive boy who
played the leading rôle.
We do not hear much about the youthful father of pneumatic engineering,
possibly because he lived so very long ago, but his story is fully as interesting
as that of Watt or Galileo or Newton. Young Ctesibius dwelt in the city of
Alexandria, Egypt, 250 years before the birth of Christ. His father kept a
barber shop, and the young lad used to watch his father practice his tonsorial
art on the Greek and Egyptian dandies of the time. No doubt Ctesibius’s
father expected to make a first-rate barber of his son, but history does not tell
us much about his early life.
The barbers of those days had their mirrors as do the barbers of the
present time. But a mirror in those days was a treasured possession. It
consisted of a brightly polished plate of metal in which a person could see
himself “darkly” or it might have been a plate of glass with a black backing.
These mirrors had to be carefully preserved from injury and from moisture,
and so, instead of having them mounted on the wall as in a modern barber
shop, they were stowed carefully away and brought out only after the
tonsorial artist had completed his operation and was ready to exhibit his
finished product to the customer.

THE BOY WHO DISCOVERED COMPRESSED AIR

Now in the tonsorial parlors of Ctesibius’s father the precious mirror was
suspended above the head of the customer and when the barber had finished
the shave or haircut he pulled down the mirror and let the customer survey
his remodeled countenance. After the customer viewed himself to his heart’s
content he merely released the mirror and it was automatically drawn back
into place by a counterweight that slid in a case fastened to the wall. Young
Ctesibius noticed that every time the mirror was released a curious whistling
sound came from the case in which the counterweight moved. No doubt this
phenomenon had been recurring day after day for years, but it excited no
more curiosity than would a squeaky door, until, one day, the barber’s son
happened to notice it. Immediately he was all curiosity. No one knew
anything about air in those days and the boy could get no satisfactory
explanation of the phenomenon, so he started an investigation of his own. He
found that the counterweight fitted very closely in its case and when it
dropped it forced a stream of “wind” out of a crevice which produced a
whistling sound. That set Master Ctesibius to thinking. He had discovered a
method of harnessing the wind. No more barber shop for him; he was
launched upon a career of scientific research and invention.
The first use he made of his discovery was to build a pipe organ which
was driven by a water wheel and hence was known as a water organ. But
there were other and more lucrative fields for the newly discovered power.
Being invisible, compressed air proved a most valuable medium for
performing seemingly miraculous tricks with which the corrupt priesthood of
that time hoodwinked the public. Naturally such air-controlled apparatus was
kept secret, and we have only a meager record of a few of the ingenious
devices used in the temples. However, Ctesibius made many scientific
discoveries and became the most famous mathematician and scientist of his
age. We have read in Chapter IV of his famous water clock adjusted to record
hours of varying length according to the season.
While Ctesibius is credited with being the first man to make scientific use
of compressed air, the use of free air or wind as a power far antedates him.
Sailing vessels were probably in use long before windmills were invented. As
pointed out elsewhere, windmills possessed an advantage over water wheels
in that they could be placed anywhere, instead of being confined to the banks
of streams. They were widely used for pumping water, grinding grain, and
sawing wood until the steam engine arrived and displaced them.

Although wind power is but little used to-day, air is much more widely
used in modern machinery than is generally realized. A catalogue of the
various devices in which it plays a prominent part is likely to prove
astonishing. For instance, we employ it to bore through rock, to stop the
speeding express train, and even to quell ocean billows. Being elastic and
compressible, it makes an ideal spring for the storage of power and a cushion
for absorbing shocks. It is also used to fight back water and permit men to
work in the depths of the sea or in water-bearing sand and earth.
Despite his extensive use of air Ctesibius knew nothing of the
atmospheric pressure. It was not until the seventeenth century that
atmospheric pressure was discovered and measured. It was then learned that
there is no such thing as suction.

RAISING WATER WITH ATMOSPHERIC PRESSURE

FIG. 40.—SECTIONAL VIEW OF A
SUCTION PUMP

A suction pump should be called an atmospheric pump. The operation of
such a pump is illustrated in Figure 40. A piston A slides in a cylinder B.
There is an opening in the bottom of the cylinder which is normally closed by

a clack valve C that opens upwardly. There is a similar valve D in the piston
A. When the piston is pushed down it compresses the air in the cylinder,
closing the valve C while valve D opens, permitting the air to escape. Then
on the upward stroke the valve D closes and valve C opens permitting air to
flow into the cylinder. In this way the air in the pipe and cylinder are
exhausted after a few strokes. As the air is rarefied and the pressure is
reduced above the column of water in the pipe the greater pressure of the
water outside the pipe forces the column to rise until it eventually flows
through the valve in the piston and out of the spout of the pump. The
maximum height to which water can be raised by a suction pump is thirty-
four feet but in actual practice the lift seldom exceeds twenty-six to twenty-
eight feet because the fit between the cylinder and piston is not perfect.

FIG. 41.—CONVENTIONALIZED SECTIONAL VIEW OF A
FORCE PUMP

When water is raised to a greater height a force pump is used. Such a
pump is shown in Figure 41. The pump cylinder A has two valves B and C.
The valve B opens upwardly and valve C opens downwardly. The piston D is
a solid member containing no valve. When the piston rises the valve C closes

and valve B opens, letting water into the cylinder. On the reverse stroke the
valve B closes and the descending piston forces the water out through valve
C into pipe E. The height to which the water may be lifted depends upon the
power applied to the piston and not upon atmospheric pressure. In a fire
pump two force pumps are used which alternately deliver water into an air
chamber. The air is compressed by the water that enters the chamber and
exerts a steady pressure on the water, forcing it out through the fire hose in a
stream that is practically steady.
It is a decided disadvantage to install a force pump in a deep well because
of the mechanical difficulty of operating the piston at a great depth. Often the
suction and force pump principles are combined. The force pump piston and
cylinder are located twenty-six and twenty-eight feet above the level of the
water in the well with a pipe leading down into the water. The water is forced
up into the cylinder by exhausting the air in the cylinder and pipe and then is
forced out of the cylinder and up a pipe to the top of the well. This also has
its disadvantages. In deep wells the pump piston must still be located and
operated at considerable depth.

THE AIR LIFT

A much more simple pump for deep wells is the air lift in which there are
no valves and no piston. The pump consists of two pipes that are let down
into the water. (See Figure 42.) The larger pipe is open at the top and bottom,
and the smaller pipe discharges air into the bottom of the larger one. This air
being directed upward has a lifting effect, and mingling with the water in the
pipe produces a sort of froth which is so much lighter than solid water that
the atmospheric pressure on the water in the well is sufficient to raise the
froth. The water is thoroughly aerated and to a large extent purified by this
system of pumping, so that the air lift commends itself particularly for city
waterworks. Sometimes a series of air lifts are used which lift water by
successive stages to a greater height than would be possible with a single
direct lift.

FIG. 42.—PUMPING WATER WITH
COMPRESSED AIR

EXCAVATING THROUGH QUICKSAND

FIG. 43.—SECTIONAL VIEW OF A PNEUMATIC CAISSON

Centuries ago it was realized that it would be possible for men to descend
into the open sea if they were protected by a bell-shaped chamber, for the air
trapped in the chamber would furnish them with oxygen requisite for
breathing purposes, and would prevent the water from drowning them out.
This same idea of a diving bell is used on land when sinking a shaft through
quicksand or water-bearing strata. A large box or caisson is used. (See Figure
43.) This box may be either cylindrical or rectangular, and it is open at the top
and bottom. The lower edges of the box are shod with steel and form cutting
edges that will sink into the soil that is being excavated. At a height of about
seven feet above the bottom of the box there is a transverse diaphragm known
as the deck, and the space below is known as the working chamber. This deck
is very strongly constructed, as it has to support the weight of the concrete
shaft that is built above it. Laborers, commonly known as “sand hogs,” enter
the working chamber and dig out a shallow pit in the floor of clay or sand.
This pit is then extended to the cutting edges of the caisson. The caisson thus
undermined settles down into the excavation and another pit is started. In this
way, step by step, the caisson is sunk into the ground. In order to overcome

the friction of the caisson against the sides of the excavation and to insure its
sinking, it is heavily weighted. When water-bearing sand is reached,
compressed air is admitted into the working chamber to force the water out.
When the air pressure is greater than the water pressure it drives the water out
of the sand in the working chamber, so that the men can work in perfectly dry
ground, even though the surrounding sand may be so saturated with water as
to form a quicksand.
Of course the farther the excavation proceeds below the water level the
greater the air pressure required, and the caisson would be blown up out of
the ground by this air pressure or would float on the water were it not for the
weights with which it is loaded. When an open shaft is to be dug, pig iron is
loaded on the caisson to force it down, but in most work the object is merely
to sink a concrete column down to rock and so the caisson is filled with
concrete above the deck. Sections are added to the caisson as it sinks into the
ground, and these sections are filled with concrete. This method of building
the column facilitates the work of laying the concrete, and at the same time
provides the weight necessary to overcome the buoyancy of the caisson and
the skin friction on the side walls of the excavation.
After the caisson has been carried down to rock and a good seat has been
blasted out of solid rock, the working chamber is completely filled with
concrete and the concrete shaft is thus anchored to the rock.

THE AIR LOCK

Access to the working chamber is had through a central shafting. In order
to hold the air pressure in the working chamber and yet provide for the
entrance of men and materials, an air lock is fitted to the upper end of the
shafting. This air lock, as shown in Figure 43, consists of a chamber formed
with a trapdoor at the top and the bottom. Both doors open downwardly. To
enter the caisson, the bottom door of the chamber must first be closed and
means are provided for doing this from outside the air lock. The compressed
air in the chamber is then let out through a valve, and when the pressure
drops almost to normal the upper trapdoor falls open of its own weight,
giving access to the chamber. After entering, the upper door is closed while
compressed air is admitted into the chamber; the air pressure then serves to
hold the upper trapdoor closed. The bottom door, in the meantime, has been
kept closed by the air pressure below, which is greater than that above the

door. But after sufficient air has been introduced into the chamber to equalize
the pressure on both sides of the lower trapdoor, it falls open of its own
weight. The occupants of the chamber can then proceed down a ladder to the
working chamber. When leaving the caisson, the action of the air lock is
reversed. The bottom door is pushed up and held closed for a moment while
air is released from the chamber, when the greater pressure beneath will hold
the door closed, and after the pressure within the air lock has been lowered
practically to normal, the upper door drops of its own weight, permitting the
occupants of the chamber to climb out. The same process must be undergone
by buckets loaded with sand or earth from the excavation and by empty
buckets returning to the working chamber.
More time is required for a man to pass through an air lock than for a load
of sand or any inanimate load. In some of the larger caissons a separate small
air lock is provided just for the use of the workmen. In the air lock the
pressure must be built up slowly so that it will permeate a man’s whole
system. When we realize that the pressure that men have to support in caisson
work may amount to from fifty to one hundred tons on the whole body, it is
difficult at first to understand why the body is not flattened out like a
pancake. It is only by permitting the system to absorb the pressure so that
there is as much internal pressure as that outside that a man is able to enter a
compressed air chamber without harmful results.

THE CAISSON DISEASE

Compression is rather annoying to a man who has not experienced the
sensation, but the principal danger comes in decompression, particularly after
a person has been in the working chamber for a long time. When breathing
compressed air much larger volumes of oxygen are taken into the lungs at
each breath than in the ordinary atmosphere, and one feels decidedly
exhilarated by this unusual supply of stimulating oxygen. But with the
oxygen large volumes of nitrogen are taken into the system as well. The
nitrogen permeates the blood while the oxygen is consumed and exhaled in
the form of carbon dioxide. The longer a man is exposed to the pressure the
more nitrogen does he absorb. When the pressure is released suddenly the
nitrogen begins to froth, just as a bottle of soda water does when the stopper
is removed. The nitrogen bubbles in the small veins stop the circulation and
produce the dreaded “caisson disease” which makes itself felt in the form of
severe cramps and excruciating pains. Not infrequently this disease ends in

death. By reducing the pressure gradually the nitrogen is enabled to pass off
completely without bubbling or frothing, just as it is possible to let out the
gas from a soda bottle without frothing by permitting it to escape through a
pin hole in the stopper. The surest cure for a victim of the caisson disease is
to put him immediately into what is known as a “hospital tank” and build up
the pressure in the tank equal to that which he has just been subjected to in
the caisson, after which the air in the tank is let out so slowly that there is
plenty of time for the nitrogen to pass off without forming bubbles.
A pressure of forty-five pounds per square inch above that of the
atmosphere is considered a severe pressure for excavation work. But work
has been carried on in pressures up to fifty-two pounds, corresponding to a
depth of 120 feet below water level.
Now that the cause of the caisson disease is understood formulas have
been worked out to insure proper decompression. On one occasion a diver
descended 306 feet into the ocean where the water pressure was 133 pounds
on every square inch of his body. This meant that the air which was pumped
down to him had to be compressed to the same pressure. The diver actually
remained at the bottom only a very short time, but it took two hours and
three-quarters to bring him to the surface. He came up half the distance very
quickly and then had to rest on the bottom rung of a Jacob’s ladder. The rungs
on this ladder were ten feet apart and he was instructed to rest on each rung a
certain specified time. When he was ten feet below the surface he had to wait
three-quarters of an hour for the last trace of nitrogen absorbed by his blood
to pass off.

BORING TUNNELS THROUGH RIVER BEDS

It is comparatively simple to sink a vertical shaft into water-bearing soil,
but a horizontal shaft involves serious difficulties. The action of a diving bell
is easily illustrated by inverting a tumbler and pressing it down into a basin of
water. The air trapped in the tumbler will keep the upper part of the glass dry,
and by inserting a tube in the tumbler it is possible to fill the tumbler so full
of compressed air as to drive out all the water. This is virtually what is done
in the caisson; but when excavating a horizontal bore, the caisson must be
turned on its side. Turn the tumbler on its side and it is impossible to keep the
water out of it, no matter how much air we may blow into it. The reason for
this is that the pressure on the open end of the tumbler is not uniform. At the

bottom, where the water is deeper, it will be greater than at the top. If air is
pumped in to equalize the water pressure at the upper edge of the glass, it will
not prevent water from flowing in at the bottom; and if it be equal to that at
the bottom, the water pressure at the top cannot hold the air in and keep it
from pouring out.

FIG. 44.—SECTIONAL VIEW OF A TUNNEL SHIELD

Fortunately most of the soil through which a subaqueous tunnel is driven
is not very fluid. It is either sticky, as in clay, or sluggish enough to prevent
the water from flowing in rapidly. If there is enough cover of silt or earth
above the tunnel bore, it will help to hold the air in the tunnel. When the bore
comes very close to the surface of the bed of the stream that is being
tunneled, loads of clay are dumped along the line of the tunnel to provide the
requisite cover. In tunnel boring a shield is used which is the equivalent of
the caisson in vertical boring. The shield is a cylindrical box with a
diaphragm across it corresponding to the deck of the caisson. (See Figure 44.)
In front of the diaphragm there is a small working chamber which is
protected above by an extension of the shield known as an apron. In the
diaphragm there are a number of doors at different levels, which may be
closed in case of danger. If work is proceeding near the top of the shield, the
upper doors are opened and the pressure is regulated to equal the water
pressure at that level. If the work is carried on near the bottom of the shield,
the upper doors are closed and only the lower doors are open, and the
pressure is increased to equal the water pressure at that point. Sometimes the
material is of such a nature that the men can safely pass out of the doors into

the working chamber outside, but more often it is possible to work only
within a limited area immediately in front of the doors.
When the material is very soft it is often unnecessary to do any actual
excavation by hand in front of the diaphragm. The shield is merely pushed
forward through the mud or silt and the doors are opened to let the material
flow in through them. Workmen dig out this mud and it is hauled out of the
tunnel. Whenever bowlders are encountered it is necessary for the men to
work outside of the diaphragm to chip away the rocks with compressed-air
drills, or else bore them and blast them with small charges of dynamite.
In quicksand the material is so fluid that it is unsafe to open the ordinary
doors of the caisson, and they are then provided with shutters which are
raised one at a time, to permit of operating on a very small section of the head
of the tunnel. After enough material has been excavated from in front of the
shield, the latter is pushed forward and the excavating is renewed.
Unlike caisson work, the weight of the shield is of no assistance in
making it penetrate the soil, nor is it possible to move the entire lining of the
tunnel with the shield. The tunnel is lined with rings of cast iron which are
bolted together, the rings themselves being made up of heavily ribbed curved
plates. The shield is formed with a “tail” which fits over the end of the tunnel
line like a cap. When the shield is to be pushed forward, a set of hydraulic
jacks are fitted between the end of the tunnel lining and the diaphragm of the
shield, and by means of these the shield is given a shove forward far enough
for a new section of the cast-iron lining to be added within the tail. The
tunnel-lining rings are usually sixteen inches wide so that it is customary to
move the shield ahead sixteen inches at a time or just far enough for a new
ring of lining to be installed. Of course, the tunnel is fitted with air locks by
which men can enter the working section without permitting the compressed
air therein to escape, and these locks are just like those used in sinking a
caisson, except that they are horizontal instead of vertical.

QUELLING OCEAN BILLOWS WITH AIR

Air is also used in another and very novel way to battle against water. In
this case it is not quiet water pressure, but the tremendous power of ocean
storms that is combatted.
The influence of a shoal upon ocean waves has often been observed. A
sand barrier even when submerged to a depth of twenty or thirty feet will

break the waves of a heavy storm and leave an area of comparatively quiet
water behind it. The reason for this is that the water in the waves does not
travel with the waves, but undergoes local oscillatory motion. This motion is
in the form of circular or elliptical currents which travel in a vertical plane.
When a sand bar is encountered it interferes with these local currents and
breaks up the waves.
Knowing this to be the case, it occurred to Mr. Philip Brasher that some
other means of disturbing the rhythmic movement of the water might be
found, and he determined to try the experiment of using compressed air for
this purpose. Accordingly he laid a perforated pipe under water and
connected it with an air compressor. Then when a storm arose air was
pumped into the pipe and it rose in bubbles through the water. The effect of
this upward movement of air was instantly observable. It upset the rhythmic
water currents and the waves which struck this wall of air bubbles curled and
broke as if they had encountered a shoal of sand.
Several exposed piers on the Pacific coast have had a pneumatic
breakwater built around them so as to protect them or ships lying alongside
from being pounded by the waves. There is no expense attached to the
breakwater except in time of storm when the air pumps must be kept going.
One important advantage of the breakwater is that it does not block
navigation. A ship can sail right over the wall of bubbles and find refuge
behind it.

CHAPTER VIII

AIR SPRINGS AND CUSHIONS

U
NLIKE water, air is a highly compressible, elastic fluid, and as such
furnishes an excellent medium for the storage of energy. It acts just
like a clock spring into which energy may be introduced and stored
by winding or compressing the spring. The energy remains locked up
in the spring and when the spring is released, it gives back just as much
energy as was put into it, except for slight frictional and heat losses. Air is a
much better spring than steel or any other metal because it never loses its
elasticity from fatigue and because it has an enormous capacity for the
storage of energy. It possesses one serious drawback, however. Much of the
energy that is expended in compressing it is converted into heat. If the air
were to be used immediately and without transmitting it to a distance, there
would be no advantage in extracting the heat, but heat cannot be stored in air
for long and it would gradually escape from the storage reservoir or air
receiver and from the pipes leading the air to the machines that it was to
operate. As the heat escaped it would lower the pressure of the air and hence
much of the energy would be lost.

HEAT OF COMPRESSION

In Chapter V we described a hydraulic system of compressing air and
noted that one of the advantages of this system is that it delivers air cooled to
the temperature of the water. This, of course, does not mean that there is no
loss due to heat. The air bubbles as they are compressed are cooled by the
water that compresses them; in other words, the heat of compression passes
off into the water, making the water warmer than it would otherwise be. Heat

is not produced without expenditure of energy and a certain proportion of the
water power is thus wasted.
In most cases air is compressed by steam or electrically driven
compressors, and in such machines the heat due to compression is a serious
matter. The air cylinders are water-jacketed to carry off the heat. But air is a
poor conductor; it acquires heat faster than it can give it off to the water
surrounding the cylinders. In compound air compressors the air compressed
in one cylinder is cooled before being passed on to the next cylinder, where it
is further compressed. The heat loss in compressing air in a single stage up to
100 pounds gauge pressure is about 30 per cent. Air that enters a compressor
at the normal pressure of the atmosphere and with an initial temperature of 60
degrees F., if not cooled will become heated to 415 pounds gauge pressure.
The higher the initial heat of the air, the greater the rise of temperature. If a
volume of air be subjected to 294 pounds gauge pressure, it will occupy
about one-tenth of its former volume. If the air was introduced into the
compressor at zero, it would acquire a temperature of about 650 degrees; if
introduced at 60 degrees, it would show an increase of about 800 degrees;
and, if started at 100 degrees, it would show an increase of 900 degrees in
passing through the compressor. This shows the advantage of compressing
the air in stages and cooling the air between stages.
Sometimes the heat developed is sufficient to produce a disastrous
explosion. Air is noncombustible, but the oils used to lubricate the
compressor are vaporized by the heat and when mixed with air form a
powerful explosive. Care has to be taken that none but high-grade oil with a
high flash point be used in the compressor and that the temperature of
compression does not rise to near the flash point lest the vaporized oil be
ignited.
That fire can be produced by sudden compression of air has long been
known in the Philippine Islands. The natives use a small air tube with a close-
fitting plunger. Combustible matter is placed in the bottom of the tube, and
on striking the plunger a sharp blow this is ignited.
When compressed air is used in an air motor it expands and in so doing
absorbs heat. The more rapidly it expands, the more heat it absorbs. This heat
it extracts from the motor and from the atmosphere into which it escapes, and
it is a common occurrence to find a thick coating of frost around the exhaust
port. This is due to condensation of moisture in the atmosphere or in the
compressed air itself, which, because of the rapid extraction of heat, is

converted into snow. On cold days enough frost may be produced in the
exhaust pipe to clog it and interrupt the operation of the motor, and frost
sometimes clogs the air lines leading to the motor.

WHARF ON THE PACIFIC COAST PROTECTED BY A PNEUMATIC
BREAKWATER
Air issuing from the submerged perforated pipes breaks up the waves

GENERAL VIEW OF A SUN POWER PLANT IN EGYPT

CLOSE-UP OF ONE OF THE REFLECTORS SHOWING THE
BOILER

The fact that compressed air on expanding is cooled, makes it an ideal
power for use in mining machinery. Steam is inconvenient because of the
difficulty of transmitting it to the machines without loss of heat, because it
would heat the machines so that they cannot be handled readily and because
the exhaust steam would fill the mine with an impenetrable fog; electricity is
dangerous in mines that are apt to contain explosive gases, because the wires
are liable to be broken and cause sparks by short circuiting, and because
sparks are likely to form between the brushes and commutators of the motors;
but compressed air has none of these objections, and, furthermore, the
discharge from the machines furnishes the operators with ample supplies of
fresh cool air which drives out disagreeable and dangerous gases.

AIR-DRIVEN HAMMERS

The ordinary rock drill is really a pneumatic hammer. The tool, which is
chisel-shaped, is used as a hammer to pound a hole in the rock. The tool is
driven up and down or in and out by compressed air bearing alternately on

opposite sides of a piston. The elasticity of the compressed air acts as a
cushion to relieve the machine from shock. The drill is mounted upon a
tripod in such a way that it may be operated in any direction.
The pneumatic riveter is another form of compressed-air hammer. The
machine is held in the hands, and the tool, which is rapidly reciprocated by
air pressure, pounds the red-hot shank of a rivet. While this is being done an
assistant holds a hammer against the head of the rivet. However, there is a
type of riveter which has a U-shaped frame. One arm of the frame carries the
reciprocating tool while the other reaches around and bears against the head
of the rivet.
All sorts of tools have been built in which a small air-driven motor
furnishes the motive power. There are hand drills in which the tool is
revolved by a set of pistons, shears for shearing sheep which operate
somewhat on the principle of hair clippers, and pneumatic chisels used for
chipping stone. Pneumatic motors are widely used in operating cranes and air
hoists. They consist of a simple cylinder and piston, and are used for short,
direct lifts of all sorts.

STOPPING TRAINS WITH AIR

Air has played a most important part in transportation. When the air brake
was first introduced its purpose was to prevent collisions and provide greater
safety of operation. It was not generally realized that efficient air brakes are
not only a safety precaution, but a means of increasing schedule speeds. The
more quickly a train can stop, the better speed it may make, particularly on a
schedule that calls for frequent stops.
In the first air brake invented by George Westinghouse, the locomotive
was provided with a reservoir in which air was stored and compressed by
means of a steam-operated air pump. The cars were each provided with a
cylinder and piston connected to the air reservoir through a valve
conveniently located in the engineer’s cab. The piston of the air cylinder was
connected with the air brakes so that whenever the engineer wished to stop
his train he merely turned on the compressed air and all the brakes in the train
were operated. This was a great saving over the previous system of providing
brakemen to operate hand brakes.
Unfortunately, the problem of stopping a train was not as simple as all
this. On a long train the cylinders near the engine were the first to receive

pressure sufficient to operate the brakes, and as a result, the forward part of
the train was retarded more than the rear part at the start of the brake
operation, and the train came to a stop with a series of jolts. Another serious
disadvantage was the fact that an enormous reservoir was required to furnish
all the air necessary for a long train. But the most serious drawback was the
fact that occasionally a train broke apart and then the engineer was powerless
to control the brakes of the detached portion of the train. If the accident
occurred on a down grade, there would result a collision between the cars
running by their own momentum and gravity and those attached to the
engine. This led to the present system of reversing the process which consists
in keeping air pressure constantly in the train pipe and setting the brakes by
relieving the pressure in the train pipe.
Each car is provided with its own cylinder which furnishes the necessary
air for the operation of its brakes. There is, of course, a main cylinder on the
locomotive in which air is pumped at high pressure by a steam-operated
pump. When the pressure of the main reservoir falls below a predetermined
amount, the air pump starts operating automatically and continues until the
requisite pressure is restored. Air from the reservoir is fed to the train pipe at
a certain pressure and feeds the local reservoirs on the cars of the train. At
each car it passes through a very ingenious triple valve, which consists of a
cylinder with a double piston, one operated by pressure in the train pipe, and
the other by pressure in the local cylinder. The piston operated by the
pressure of the train pipe is larger than the other and consequently the valve
piston is normally pressed back, uncovering a small port through which air
from the train pipe feeds into the local reservoir. In this way the air in each
local reservoir is maintained at the same pressure as that of the train pipe.
Whenever air is let out of the train pipe, the piston is pushed out by the
excess pressure on the local reservoir side and uncovers another port which
permits air to flow from the local reservoir to the brake cylinder operating the
brakes. The advantage of this system is that each car is always supplied with
sufficient power to act on the brakes immediately without having to draw its
supply of air from the main reservoir. In case the train breaks apart, the air in
the train pipe escapes and the brakes are set automatically.
There have been a number of improvements in air brakes aimed to make
the operation of the brakes more uniform and to insure immediate action,
even on a very long train. Modern express trains weighing 920 tons and
traveling at a velocity of 60 miles per hour, can be brought to a standstill in
860 feet, or practically their own length. Automatic arrangements are

provided to insure the application of the brakes at graduated rate, except, of
course, when the emergency brakes are applied. As the speed of the train
slows down the pressure is gradually relieved, otherwise the train would stop
with a severe jolt. The rate of applying the brakes so as to provide a smooth
retardation depends in large measure upon the weight of the train.
On the New York subways, it is interesting to note, every passenger who
boards a train has his weight recorded by the brake mechanism, and
allowance is automatically made for the inertia that his mass adds to the train
when it is in motion. The weight operates through a system of levers to
control the amount of pressure that is applied to the brakes so that when the
engineer operates the brake lever, he does not have to consider whether the
cars are light or jammed full of passengers; the brake mechanism itself takes
care of this.

PROPELLING CARS WITH AIR

If air can be used to stop a train, why cannot air be used to propel it? This
question occurred to many inventors and they answered it by building air-
propelled cars and locomotives. Pneumatic cars were tried out on street
railways, but they have had to give way to electric cars which do not need to
carry their power around with them, but can draw it from a central power
plant through a trolley wire. In only a few situations, such as in mines where
electric sparking is feared, are air-propelled cars and locomotives still used to
any considerable extent.
However, air plays another and highly important part in transportation
and here it is employed not to deliver energy stored in it, but to serve as a
cushion. Without the soft, flexible grip of the air-filled rubber tubes with
which automobile wheels are shod, high-speed motoring would be practically
impossible. There is nothing that can compare with air for absorbing shocks
and unevennesses in the road. Whenever an obstruction is encountered, not
only is the shock absorbed by elasticity of the air, but the impact is
immediately distributed uniformly over the whole tire, so that the strain on
the tire is not localized and the life of the tire is correspondingly increased.
There have been many attempts to introduce substitutes for pneumatic tires,
such as combinations of metallic springs and straps, but these have failed,
chiefly for the reason that they cannot distribute the shock as the pneumatic
tire does. Consequently they are not only liable to damage, but they do not

absorb the obstructions as readily as the pneumatic tire does and the vehicle
which they carry is subjected to heavy stresses and strains.
Air as a cushion is used to prevent the rebound of the springs of an
automobile and is also widely employed in machinery to absorb the
momentum of moving parts or to slow the action of a spring. In a door check,
for instance, a powerful spring is provided which would slam the door shut
were it not for the cushioning action of air. A plunger is connected to the door
and slides in a cylinder on the door frame. The air compressed by the plunger
can escape only very slowly through a small port.

AIR CUSHIONS FOR ELEVATORS

Air cushions are used in elevators to prevent too rapid a fall of the car in
case of accident. The lower part of the elevator shaft is completely inclosed
and fitted with steel doors to form an air pocket. The car fits the shaft closely
enough to compress the air under it when it is moving downward. At normal
speeds, this air escapes quite readily around the sides of the car and through
cracks in the doors, but when the speed is excessive the air cannot escape fast
enough and sufficient pressure is built up to retard the car so that it will strike
the bottom with a moderate impact not at all dangerous to the passengers.
In the Woolworth Building, New York, the highest elevator shafts are 680
feet high and the air pockets are 137 feet deep—i. e., they reach up to the
tenth story. If the car broke away from its supports at the top of the shaft it
would be traveling at the rate of 132 miles an hour when it struck the air
pocket, but before it reached the bottom the air would bring it practically to a
stop. Imagine a heavy automobile traveling at 132 miles per hour and brought
down to a standstill in half a city block! The passengers would be hurled out
of their seats, but in an elevator the passengers are standing and can brace
themselves against the pressure produced by their own momentum. The
velocity acquired in falling 543 feet to the air pocket must be overcome in
137 feet or ¼ of the distance. This means that the weight of each passenger is
multiplied by four. A man who weighed 150 pounds would find that his
pressure on the floor of the car had mounted to 600 pounds. One of the
inventors of the pneumatic cushion for elevators was killed when testing out
a car, not because of the impact of the car, but because he was foolish enough
to sit in a chair. The chair gave way under his suddenly acquired weight and
the poor man was fatally stabbed by one of the splinters.

Air jets are used for a variety of purposes ranging from tamping railway
tracks to painting buildings. When a track is depressed under the tamping
action of trains passing over it the ties must be raised and new ballast
introduced under them so as to bring them up to level. In order to save hand
labor and insure the perfect filling of all cavities a pneumatic tamper is
sometimes used. The ballast, consisting of sand or gravel up to ¾ inch in
diameter, is fed out of a hopper and meets a blast of air that hurls it into place
like shot from an air rifle. This furnishes a very solid and compact road bed.
It is in much the same way that weather-stained stone walls are cleansed
by means of a sand blast. The sand particles projected by the jet of air act like
myriads of tiny bullets which chip away the face of the stone.

LAYING CEMENT WITH AN AIRGUN

It is after this same fashion that the cement gun is used to project cement
against wire reenforcement to form walls of buildings. Carl E. Akeley was
led to the invention of the cement gun by his efforts to find an expeditious
and economical method of mounting specimens of large animals for the Field
Museum in Chicago. He constructed a pneumatic device for spraying cement
and water upon a canvas-covered framework, thus building up a body upon
which the skin of the animal could be mounted. This machine was improved
and tried out successfully, on a large scale, in constructing buildings.
The machine as now constructed consists of a hopper into which a proper
mix of sand and cement is introduced. Compressed air blows this mixture out
of a nozzle. Here it meets a jet of water also propelled by compressed air. The
water, sand, and cement combine and strike the wall or surface to be coated
with such an impact as to make a compact fine-grained coating known to the
trade as “gunite.”
Large surfaces can be painted much more readily and more evenly with
compressed air than with a brush. A widely spreading air jet is used which
draws the paint out of a receptacle, breaking it up into minute droplets that
are projected as a mist against the surface, covering it with a uniform coating.

AIR AS A TENSION SPRING

So far we have been considering air as a compression spring. It may also
be employed in a manner somewhat analogous to a tension spring. When air

is exhausted from a receptacle we have a partial vacuum which will produce
work, but in the opposite direction from that produced by compressed air. Of
course there is no such thing as suction, and it is the pressure of the
atmosphere which is employed to do the work.
We are apt to overlook the fact that a vacuum cleaner depends upon
atmospheric pressure to drag the dust and dirt out of a carpet. A vacuum
cleaner would not work on the moon, where there is no atmospheric pressure.
The apparatus consists of an air pump, usually driven by an electric motor,
which exhausts, or partially exhausts, the air from a foot piece that is dragged
along the carpet. As the air under atmospheric pressure rushes in through the
carpet to take the place of the air that has been pumped out, it carries with it
all loose particles of dirt. The dirt is filtered out of the air or a mechanical
trap is provided to catch and retain the dirt while the air is allowed to escape.
Large-scale vacuum cleaners are used for cleaning city streets. The dirt is
loosened by revolving brushes and is then drawn up by atmospheric pressure
into a tank.
Another use of atmospheric pressure is to be found in the pneumatic tubes
which convey mail from one post office to another. Air is exhausted from the
tube and when a carrier is inserted which fits the tube closely the atmospheric
pressure behind it forces the carrier along to its destination. The same system
is used to carry money to and from the cashier’s office in department stores.
In later developments of the pneumatic mail carrier compressed air was
used back of the carrier, but the principle of operation was not altered. In
either case propulsion is effected by the difference of air pressure on the
opposite sides of the car.
In 1869 Alfred E. Beach built an experimental subway line under
Broadway, New York, near Warren Street. The line was only 200 feet long. A
cylindrical car large enough to hold eighteen people, fitted the bore snugly
and was propelled in one direction by compressing the air in the tunnel and in
the other direction by exhausting the air.

CHAPTER IX

POWER FROM HEAT

T
HE TERM “water power” is a misnomer. There is no power inherent in
water. It is gravity that makes water fall in cataracts or flow down a
river bed, and hence it is the force of gravity that is responsible for the
turning of our turbines and Pelton wheels. Water is merely the medium
through which the force of gravity acts.
In the steam engine, water, again, serves as a medium and it is the energy
of heat that is actually the working force. A closed vessel is partly filled with
water and heat is applied to it. The water grows hotter and hotter until at a
temperature of 212 degrees it begins to vaporize. The temperature of the
water remains stationary until the space above the water is completely filled
with steam at a pressure equal to that of normal air pressure. The steam gauge
then registers zero. Continued application of heat raises the pressure of the
steam and also raises the temperature of the water. When the steam gauge
shows a pressure of 25 pounds per square inch, the water temperature is
nearly 267 degrees; at 100 pounds it is over 337 degrees; at 200 pounds it is
387 degrees; at 500 pounds it is about 467 degrees. As steam is drawn off
from the boiler a proportionate amount of water turns immediately into steam
to take its place. If the boiler should burst, the entire mass of water would
instantly flash into steam because its temperature is far above the boiling
point at normal air pressure. That is why the explosion of a steam boiler is so
violent. If the boiler were entirely filled with steam the effect of an explosion
would not begin to be so destructive as if the boiler were half full of water. It
is really the explosion of water that does such serious damage.
When the steam pressure in a boiler corresponds to the temperature of the
water it is said to be saturated. The water in a boiler boils violently when the

steam is drawn off rapidly and tiny droplets of water are carried off in the
steam, producing what is known as wet steam. Steam that carries no water
particles in suspension is called dry steam. When the steam is heated above
the temperature of the water by means of an auxiliary heating device or by
some peculiar construction of the boiler, it is called superheated steam.
In order to economize fuel it is highly important that as much water
surface be exposed to the heat as possible. This may be done either by
passing the heat in tubes through the water or by passing the water in tubes
through the fire. Locomotive boilers are of the fire-tube type. The flaming
gases of the furnace pass through the boiler through a series of tubes that lead
to the stack. In the water-tube boilers it is highly important that a good and
rapid circulation of water be maintained, otherwise there might be local
generation of steam with serious consequences.

THE GIFFARD INJECTOR

FIG. 45.—INJECTOR FOR INTRODUCING WATER INTO A STEAM
BOILER

As steam is used from a boiler the water is slowly exhausted and it must
be replenished with a fresh supply. In early days of the steam engine, water
was pumped in against the boiler pressure by the use of powerful pumps, but
in 1858 a man named Giffard invented a most ingenious apparatus by which
steam of the boiler was used to force water in directly against its own
pressure. This seems like lifting oneself by one’s boot straps. When the
injector was first invented it seemed so impossible for it to work that
engineers would not accept it until it had repeatedly demonstrated its
operativeness. Even after it was accepted and in common use its mysterious

operation was a subject of discussion for years. A sectional view of a Giffard
injector is shown in Figure 45. Steam from the boiler comes down the tube A
and passes out in a jet from the nozzle B. A needle valve C may be moved
into the nozzle to reduce or shut off the jet of steam. The jet enters a conical
chamber D which has a tube E that runs down into the water reservoir. The
steam jet blows the air out of chamber D, producing a partial vacuum which
draws water up the tube E and into the chamber D. When the water reaches
the steam jet it is driven out of the chamber across a short open space into a
slightly diverging tube or receiving cone F and through a check valve G into
the boiler. At H there is a glass window through which the action of the water
jet as it rushes into the receiving tube may be watched. I is an overflow pipe
leading back to the reservoir. When the steam flows into the cone B it gathers
momentum and issues from the nozzle in a jet of high velocity. On striking
the water it combines with the water and condenses, but at the same time it
imparts its momentum to the water so that the water is given more than
enough momentum to drive it into the boiler against the pressure in the boiler.
The pressure of steam is utilized to drive the piston of an engine or the
steam may be set in motion by letting it issue from a nozzle, when its
momentum may be employed to drive a steam turbine in the same way that a
water jet drives a Pelton wheel but in either case it is heat that does the work.
The steam expands as it moves the piston and as it passes through the nozzle
its expansion is accompanied by a corresponding loss of heat.
As we have already noted, it was for the purpose of raising water that
inanimate powers were first set to work. It was with the same object in view
that steam was first employed.

HERO’S STEAM ENGINE

To be sure the first steam engine was invented by Hero, the disciple of
Ctesibius, in the second century before Christ, and it was not a water-raising
machine. It consisted of a hollow sphere (see Figure 46), mounted to rotate
and fed with steam that entered it through the journals. The steam issued
from opposite sides of the sphere through two bent tubes. The steam in
issuing from the tubes reacted against the tubes, pushing them back and
causing the sphere to revolve.
Every action is accompanied by an equal and opposite reaction. A bullet
fired from a gun kicks the gun back. In order to push the bullet out of the

barrel, the powder must have something to push against and the push against
the gun is equal to the push against the bullet. Even if there were no bullet to
be pushed the discharge of the powder would react against the gun. In order
to push its own gases out of the gun, the powder must push back against the
gun.

FIG. 46.—HERO’S STEAM ENGINE

In Hero’s engine, the steam, in order to push itself out of the sphere, must
push against the bent tubes. We have a similar reaction motor in the revolving
lawn sprinkler. The water issuing from the bent arms of the sprinkler forces
them back and causes them to revolve. Were the arms radial and not bent the
reaction would be there just the same, but it would be exerted against the
center of the wheel and hence there would be no rotation.
Reaction has nothing to do with the pressure of the atmosphere as so
many people imagine. A gun would kick just as hard and the lawn sprinkler
or Hero’s engine would operate just as well and as fast in a perfect vacuum. It
was to demonstrate the principle of reaction that Hero built his steam engine.
As far as we know it was never put to useful work and remained merely a
scientific toy.

NEWCOMEN’S ATMOSPHERIC ENGINE

The first practical use of steam power was applied to the pumping of
water from the deep mines of Cornwall. Newcomen’s engine, which
antedated Watt’s by several decades, was known as an atmospheric engine. It
consisted of a cylinder fitted with a piston, but the top of the cylinder was
open. The piston was connected to one end of a lever or walking beam, the
other end of which was connected by a chain with the plunger of a pump
situated at the bottom of the mine shaft. Little power was required to lift the
piston because it was counterbalanced by the chain and plunger attached to
the opposite end of the walking beam. The real work was done in pushing the
piston down and thereby raising the pump plunger. Steam under low pressure
was let into the cylinder under the piston to raise it and then a jet of water
was sprayed into the steam-filled cylinder. This condensed the steam,
producing vacuum and the atmospheric pressure acting on the upper surface
of the piston forced the piston down, raising the pump plunger. The engine
ran very slowly, making only about 15 strokes per minute. Later it was
improved, producing about 30 strokes per minute.

WATT’S STEAM ENGINE

Watt was the first man to build an engine in which the real work was done
by the pressure of steam as in modern steam engines. As long as the steam
engine was used for pumping water the reciprocating piston could be
connected directly to the pump plunger and it was unnecessary to exert power
on both sides of the piston, but in 1782 Watt obtained a patent on a double-
acting engine. Steam was admitted first on one side of the piston and then on
the other. The walking beam was connected by means of a connecting rod to
a crank on a shaft that carried a flywheel, and the seesaw motion of the beam
was converted into rotary motion of the wheel. This opened up new industrial
opportunities for the steam engine.
The steam was exhausted from the cylinder into a condenser, i.e., a
chamber, in which a spray of water converted the steam into water, producing
a vacuum, thereby relieving the piston of back pressure and virtually adding
that much more power to the steam operating on the opposite side of the
piston. A pump driven by the engine drew the water and the air liberated from
the condensed steam out of the condenser.

Watt invented an ingenious governor to control the flow of steam to the
engine and insure a uniform motion. (See Figure 47.) This governor consisted
of a pair of levers hinged to a revolving shaft and each provided with a ball
weight at its free end. The shaft was revolved by the engine and if the engine
tended to run too fast the balls were thrown out by centrifugal action. In so
doing they operated a throttle valve cutting down the steam supply. When the
engine slowed down the balls would drop, admitting more steam. In this way
the speed of the engine was kept within close limits. The ball governor in
improved form is still widely used in stationary engines.

USING THE HEAT IN THE STEAM

FIG. 47.—WATT’S BALL GOVERNOR

Another of Watt’s inventions which has proved of highest importance in
steam engineering was the cut off. In his first engine the piston was subjected

to the full boiler pressure throughout its stroke, and the steam that poured out
of the exhaust port of the cylinder at the end of the piston stroke was almost
as hot as that which entered the cylinder at the beginning of the stroke. The
heat that goes out in the exhaust represents just so much wasted energy. Watt
realized this and so he invented a valve which would cut off the flow from
the boiler before the piston had completed its stroke. Then the steam back of
the piston would continue to expand because of the heat within it and would
keep on pushing the piston. Of course, the pressure would gradually diminish
and there would be less power in the stroke than if the full boiler pressure
were pushing the piston all the way, but this loss of power is offset by the
saving in steam and in the fuel used to heat the steam. The point at which the
cut-off takes place depends largely upon the pressure of the steam. If the
steam is cut off when the piston has made only one-fifth of its stroke, one-
fifth as much steam will be used at each stroke as would be the case if the
steam were used nonexpansively. However, in actual practice the expansion
of the cut-off steam instead of being five times would be only about four
times, because of the clearance that must be allowed between the piston and
the end of the cylinder. If steam of 100 pounds absolute pressure is used, the
average pressure throughout the piston will be only about 57 per cent of the
full pressure of the steam in the boiler, but each pound of steam will actually
do .57 × 4 = 2.28 times as much work as it would if used nonexpansively. All
sorts of valve gear have been invented to admit steam quickly and cut it off at
the proper point to produce the most efficient result.
In low-pressure cylinders in order to prevent loss of heat through the wall
of the cylinder, the latter is steam-jacketed. In other words, there is an outer
casing surrounding the cylinder and between this casing and the cylinder
steam is admitted to keep the cylinder walls hot.
In order to make full use of the heat in steam it is, in some engines, sent
through a series of two, three, and even four cylinders. The exhaust from one
cylinder goes into a second larger cylinder. From here after doing work on a
piston it discharges into a third still larger cylinder and from that may be led
into a fourth cylinder. The cylinders must be progressively larger to allow for
the expansion of the steam.
The ordinary steam engine labors under the disadvantage of having to
start and stop its pistons at the end of each stroke. Every body possesses
inertia, whether it be moving or at rest. If it be at rest, it takes much more
energy to set it in motion than to keep it moving. In fact it would keep on

moving without further expenditure of energy were there no friction and no
forces acting against it. In order to stop the body energy must be expended to
overcome its inertia. The more rapidly a body is started and the more quickly
it is stopped, the more work must be done in overcoming its inertia. In a
steam engine not only the piston but other parts connected to it may be
required to reciprocate several hundred times per minute. A great deal of
energy is uselessly expended in starting and stopping these parts.
Many efforts have been made to produce a rotary engine in which the
piston rotates instead of reciprocating, thus doing away with the work of
overcoming inertia. However, there are serious obstacles to the construction
of such an engine, and as yet no truly efficient and practical rotary engine has
been built.

DE LAVAL’S STEAM TURBINE

However, there is another type of engine in which the steam is applied
continuously and all the parts revolve. Such an engine was the reaction
turbine invented by Hero, to which reference has already been made. Modern
turbines, however, are of very different construction. They resemble the
Pelton wheels and turbines used in developing water power, differing from
them mainly in the fact that use is made of the expansive energy of steam
which is lacking in water. In the De Laval steam turbine a wheel is used
which has a series of curved buckets all around its periphery that are closed at
the outer end by a circular rim. (See Figure 48.) Steam is directed against this
bucket, not tangentially as in a Pelton wheel, but from the side. Several steam
nozzles are employed and as the steam jets strike the buckets and sweep
around their curved surfaces they react against the buckets and drive the
wheel around. In order to operate efficiently the velocity of the steam must be
very high and the wheel must also turn at high speed. When steam flows
through a diverging nozzle its velocity is greatly accelerated by its expansive
effort. Such nozzles are used in the De Laval turbines and the steam issues
from them with a velocity which may be higher than that of a rifle bullet. The
buckets are forged and the hard-scale surface is left on them; otherwise they
would wear away quickly under the action of the powerful jets of steam.

FIG. 48.—THE DE LAVAL STEAM TURBINE

The turbine wheel may revolve at a speed of 30,000 revolutions per
minute. Such a tremendous speed has its disadvantages. If a wheel is to run
smoothly it must revolve on its center of gravity. A lopsided wheel, or one
that is mounted a little off center, produces a pounding action which imposes
a serious strain upon the bearings and the revolving parts. The wheel tries to
turn on its own center of gravity and will do so if permitted to. It is
impossible to balance a wheel so perfectly that the axis it turns on passes
exactly through its center of gravity. At ordinary speeds this slight
eccentricity is so slight that it is practically negligible, but when we have to
deal with 30,000 revolutions per minute the least divergence between the
center of rotation and the center of gravity will produce dangerous strains.
For this reason the wheel of the De Laval turbine is mounted on a flexible
shaft and on floating bearings, so that it will automatically find and turn on
its own center of gravity. In order to utilize the power developed in the wheel,
gearing must be used to step down the speed.

PARSONS EXPANSION TURBINE

The Parsons steam turbine resembles a water turbine in its action. Instead
of having a few nozzles directing steam against the buckets there is a nozzle

for each bucket, and instead of a single wheel there is a series of them
through which the steam passes, successively passing through a set of nozzles
between each wheel. The nozzles are formed of blades on the periphery of
stationary wheels. These blades are curved in the opposite direction to the
blades on the revolving wheels, as shown in Figure 49. Steam in passing
through the ring of curved stationary blades is divided up into a series of jets
which strike the curved blades of the first wheel. In passing through this
wheel the direction of the stream is reversed, and it enters between the second
set of stationary blades, which turn it back again and direct it against the next
wheel. Thus the steam pursues a sinuous course through the series of wheels.
To allow for the expansion of the steam the blades are made progressively
longer and the wheels of progressively larger diameter from the inlet to the
exhaust end of the engine.

FIG. 49.—PERIPHERAL VIEW OF THE BLADES OF A PARSONS
TURBINE

The Curtis turbine combines the De Laval and the Parsons principles. The
steam enters through a series of nozzles which are of the expanding type,
then it goes through a series of moving and stationary blades, as in the
Parsons turbine, from which it enters another set of expanding nozzles and
gains velocity and momentum before passing through the second series or
stage of moving and fixed blades. (See Figure 50.)
Steam turbines are particularly adapted for use in electric power plants.
The speed of rotation of the Parsons and Curtis types is much lower than that
of the De Laval and hence the electric generators may be directly driven by
them without the interposition of any gearing. They can be built of larger
power than the reciprocating engines because they are so economical of
space.

FIG. 50.—PERIPHERAL VIEW OF THE BLADES AND NOZZLES OF
A CURTIS TURBINE

A good comparison of turbine versus reciprocating engines is offered by
the 74th Street power station of the Manhattan Elevated Railway, New York.
This station, which was completed in 1901, was equipped with eight huge
reciprocating engines, each developing 8,000 horsepower normally, and
capable of delivering a maximum of 12,500 horsepower. The whole plant,
therefore, had a maximum capacity of 100,000 horsepower. Gradually these
units have been giving way to steam turbines of much higher power, and in
1919 there was installed one powerful turbine which alone was capable of
developing as much power as the entire plant of 1901. This is a triple-
compound turbine comprising one high-pressure turbine and a low-pressure

turbine at each side. Steam enters the high-pressure turbine at 205 pounds
pressure to the square inch and then exhausts into the low-pressure turbines,
passing from them into condensers which operate under 29 inches vacuum.
Each turbine drives a separate generator and the combined horsepower of the
whole unit is about 100,000, while the floor space occupied is only 50 by 52
feet.
The economy of space and of fuel offered by the steam turbine is of great
value in the power plants of ships, and this form of prime mover has been
installed on modern high-speed passenger liners and also on high-speed war
vessels. While in certain respects the turbine is ideal for such service, there
are two handicaps which must be overcome. In the first place, the most
efficient speed for the turbine is considerably higher than the efficient speed
of the propeller and some means must be provided for stepping down the
speed. In the second place, the turbine cannot be as economically controlled
as a reciprocating engine and its direction of rotation cannot be reversed, so
that difficulties are encountered in maneuvering the ship in harbors. It is no
simple matter to gear down the high speed and enormous power of a turbine,
However, an elaborate system of gearing has been provided for this purpose
which has proved satisfactory even in powerful battle cruisers. The British
battle cruisers with a power plant of 134,000 horsepower are driven by
geared turbines. To reverse the propellers separate low-power turbines are
used.
A more attractive system of control is to have the turbines drive electric
generators and then use the electric power to drive the propellers through
motors mounted on the propeller shafts. The electric power can easily be
controlled from the bridge and the propellers may be reversed by reversing
the motors. However, the disadvantage of the electric system is that it
occupies a great deal of space, particularly in plants running over 100,000
horsepower.

CHAPTER X

BURNING FUEL IN THE ENGINE CYLINDER

O
NE OF the handicaps of steam power is that the heat produced by the
combustion of fuel is not used directly to drive the piston. A large part
of the heat energy in coal goes up the chimney or is wasted by
radiation from the furnace walls. With anthracite coal in the furnace
the loss may be as low as 22 per cent in the very best types of boilers. In the
engine other serious losses occur, so that in the best condensing reciprocating
steam engines the power delivered is only 10 to 16 per cent of that stored in
the fuel. In locomotives the efficiency is as low as 4 to 6 per cent. In turbines
the steam is used to better advantage and the actual power delivered may run
up to 20 per cent of that in the fuel.
In internal-combustion engines the furnace and boiler losses are largely
overcome by burning the fuel right in the cylinder, where the heat energy of
the combustion may be utilized directly upon the piston. There are other
losses, however, so that the most efficient gasoline engines deliver only 28
per cent of the energy in the fuel, and coal-gas engines may run up to 31 per
cent.
A wide range of fuels may be used in an internal-combustion engine.
They may be either gaseous, liquid, or even solid. In stationary engines
hydrogen, coal gas, natural gas, blast-furnace gas, and producer gas are
employed to advantage. Volatile fuels, such as alcohol, bensol, gasoline, and
kerosene, are turned into a mist or vapor and then burned as a gas. In engines
of the Diesel type any liquid fuel ranging down to thick crude oils may be
employed, and in one type of engine, which, however, has not proved
commercially practicable, coal dust is burned in the cylinder.

BURNING AIR IN THE AUTOMOBILE ENGINE

Owing to the widespread use of automobiles, the general public is better
acquainted with internal-combustion engines than with steam engines.
Nevertheless, there are many elementary facts in connection with gasoline
engines that are not generally known. The average motorist probably does not
realize that he burns far more air in his motor than gasoline, and he probably
does not understand why it is that the mixture of gasoline vapor and air must
be compressed before it is ignited, or why only one out of four strokes of the
piston is a power stroke.
If a volume of gasoline vapor be thoroughly mixed with an equal volume
of air, the mixture will not explode. Only when there is an excess of air will
combustion take place, and the most intensive explosion takes place when
there are nine parts of air to one part of gasoline vapor. Where gasoline is
vaporized in a carburetor the best mixture is one part of gasoline-saturated air
to eight parts of pure air. Hence it is mainly air that is burned in an
automobile engine.
The energy of combustion is much greater when the mixture is
compressed. The particles of gasoline and air are forced into more intimate
contact by the compression. The same thing is true of gunpowder. If
gunpowder is ignited in the open air, it will burn quickly, but not with
explosive violence. If, on the other hand, the powder is compressed in a
cartridge and is then ignited, an explosion takes place. Nearly twice as much
gas was required in the early noncompression-type motors as is required to-
day in the compression motors of the same power.
In an internal-combustion engine the cylinder serves as a furnace. This
“furnace” must be charged with fuel, and after the fuel has been burned the
“ashes”—i. e., the products of combustion—must be removed. The piston
serves as the furnace stoker.
In the ordinary four-cycle engine the action of the piston is as follows: On
the first or down stroke of the piston a mixture of air and gasoline vapor is
drawn into the cylinder; on the next or rising stroke the charge is compressed.
Then the charge is ignited by an electric spark, and the rapid combustion of
the charge produces gases which drive the piston down. On the fourth stroke
the piston rises again and pushes the burnt gases out of the cylinder. The
piston receives energy intermittently, or only once out of four strokes, and a
flywheel has to keep it going the rest of the time. It is just like propelling a

bicycle with a single pedal and pushing the pedal every other time it comes
out. It can be done as long as the wheel is moving fast enough to carry itself
along between power strokes. Naturally a single-cylinder motor cannot be
slowed down very much without stalling, and it will not start of itself because
it needs outside help in stoking its furnace before it acquires the power to do
this job alone.

FIG. 51—SECTIONAL VIEW OF A
TWO-CYCLE ENGINE

There is a two-cycle type of motor in which the burnt gases are removed
from the cylinder, not by the piston, but by the injection of the unburnt fuel
mixture. On the upward or compression stroke the piston not only
compresses the mixture in the cylinder, but draws in a fresh charge of fuel
into the crank case, and when the piston is driven down by the combustion of
the fuel in the cylinder, the charge in the crank case is compressed until, near
the end of its stroke, the piston uncovers a port in the cylinder through which

the fuel from the crank case is forced in. (See Figure 51.) Just before this
occurs the piston uncovers an exhaust port in the opposite side of the
cylinder, and the burnt gases start to flow out before the fresh charge of fuel
pours into the cylinder. The incoming gas is directed upward so as to
completely scavenge the cylinder of all burnt gases.
There are no bothersome poppet valves in this engine. The piston itself
acts as a valve, opening and closing the inlet and exhaust ports as it slides by
them. Every other stroke of the piston is a power stroke, so that the engine
acts like a one-pedal bicycle, which receives a push every time the pedal
comes around. Unfortunately, the burnt gases are never completely
scavenged, and the fresh charge of fuel is always more or less diluted by the
product of combustion remaining from the previous charge. This represents
just so much loss of power, and may interfere with the ignition of the charge.
For this reason the four-cycle engine is generally considered more reliable
and efficient, and is far more generally used, particularly on motor vehicles.
To overcome the intermittent character of the internal combustion engine
a number of cylinders are used, which come into play successively. In the
four-cylinder motor one piston is always on the power stroke. In recent years
the number of cylinders has progressively increased from four to six, eight,
and twelve cylinders, while in racing power boats the number of cylinders
has gone up as high as twenty-four.

COOLING THE CYLINDERS

The temperature of the combustion in a gasoline engine may be over
3,000 degrees Fahrenheit. Evidently it would melt the cylinder walls were not
special provisions taken to keep them cool. The usual method is to surround
the cylinders with water which absorbs the heat, and then cool the water by
passing it through a radiator. Air driven by a fan through the radiator carries
off the heat. Of course this represents just so much wasted energy and lowers
the efficiency of the motor, but it is the most convenient way of getting rid of
the intense heat of combustion. Smaller motors, such as are used on
motorcycles, have their cylinders cooled by direct action of air on the outer
surface of the cylinder. The heat radiated depends upon the surface exposed
and the velocity of the air current. The radiating surface of the cylinders is
increased by forming them with external ribs or flanges, so that the air that
flows over them, while the machine is in motion, carries off enough heat to

keep the temperature of the cylinders within safe limits. In some systems,
particularly in the case of stationary engines, to insure a good circulation, the
air is positively driven against the flanges by means of a fan.
There are serious disadvantages in using water to cool an engine. Besides
the bother of keeping the water system supplied with water there is the
danger of clogging the radiator with lime deposits, and in extremely cold
weather the water is liable to freeze and burst the water jackets or the
radiator; for this reason, air cooling is recommended by some for automobile
engines. In certain air-cooled automobile engines the cylinders are air-
jacketed; that is, they are surrounded with casings through which the air is
sucked by a powerful fan driven by the engine shaft, so that the air is bound
to flow if the engine is turning. The cylinders are ribbed, so that they present
a large radiating surface.

Copyright, Kadel & Herbert

GIANT CAPRONI HYDROAEROPLANE WHICH WAS WRECKED
AT LAGO MAGGIORE
Seating capacity 100 persons; power, eight 450-h.p. Liberty motors

A BOAT OF STONE—THE CONCRETE STEAMSHIP “FAITH”

THE “VIRGINIAN,” THE LARGEST LOCOMOTIVE IN THE
WORLD
Length over all, 97 ft.; weight of engine, 684,000 lbs.; of tender, 214,300 lbs.;
tractive power, simple, 176,600 lbs.; compound, 147,200

Air-cooled engines have hotter cylinders than water-cooled engines and
hence in cylinders of the same size less fuel is drawn into the air-cooled
cylinder. But the fuel is used more efficiently because less of its heat energy
is wasted; so that air-cooled engines show a slight fuel economy over water-
cooled engines. On the other hand, when the air-cooled engine is overloaded
or is run at very high speeds it is liable to become overheated and may ignite
the incoming charge of gas prematurely.

THE SELF IGNITING DIESEL ENGINE

As has already been pointed out, compression of gas generates heat, and
one of the reasons for cooling the cylinders of an internal combustion engine
is to prevent the gas from exploding prematurely on the compression stroke
of the piston. In the Diesel engine, instead of avoiding such a critical
temperature it is deliberately sought, because it is the heat of compression,
instead of an electric spark, which ignites the charge. Pure air is drawn into
the cylinder on the suction stroke. This air is under ordinary atmospheric
pressure when it enters, but on the return stroke of the piston it is compressed
to about 500 pounds per square inch. This raises the temperature up to the
neighborhood of 1000 degrees Fahrenheit. Into this highly heated air a spray
of oil is injected by air at still higher pressure and immediately the oil flashes
into flame and the gases resulting from the combustion drive the piston
down.
This is a very economical type of motor. Any liquid fuel may be used,
from light gasoline to heavy crude oils, or the oils that remain after the more
volatile fuels have been distilled from them. The heavy oils have more heat

value in them than is to be found in light volatile fuels, such as alcohol,
gasoline, and kerosene, and because the oils do not throw off any
inflammable vapors unless highly heated, they can be stored more safely.
This is of highest importance on submarines and Diesel engines are
commonly used for propulsion on the surface or to drive the generators which
charge the storage batteries for submerged travel.
In order to inject the fuel into the cylinder against the pressure of air
therein, a powerful air pump is required. This does not need to be of very
large capacity, but it must compress the air to from 700 to 1,000 pounds per
square inch. It may seem at first as if the work done by the engine in
compressing the air in the cylinder and in operating the injector pump
represents so much loss, but a moment’s consideration will show that it is all
recovered. The air in the cylinder acts like a spring, rebounding when the
piston starts down on its power stroke and adding its energy to that of the
burning gases, while the air from the injector pump also enters the cylinder
and helps to push the piston down.
Diesel engines are made to operate on the two-cycle as well as the four-
cycle principle.
In one type of engine, known as the semi-Diesel, a lower compression is
used in the cylinder. This is not high enough to ignite the oil that is sprayed
in, and so a hot tube or bulb is employed at the top of the cylinder against
which the fuel jet is directed. This bulb is heated to a dark cherry red by
means of a torch until the engine has developed enough heat to keep the bulb
at the requisite temperature.

THE DOUBLE-ACTING JUNKER ENGINE

FIG. 52.—THE JUNKER ENGINE IN WHICH TWO PISTONS
RECIPROCATE TOWARD AND AWAY FROM EACH OTHER

An interesting modification of the Diesel engine is the Junker engine
(Figure 52) in which the cylinder consists of a tube open at each end. In this
there are two pistons which reciprocate toward and away from each other. Air
is compressed between them as they approach each other and fuel is injected
into this air, ignites and forces them apart. Both pistons are connected to the
same crank shaft, one pushing down and the other pulling up. The pulling
piston has a yoke on the end of the piston rod from which a pair of
connecting rods run down at either side of the cylinder to a pair of cranks on

the crank shaft. Between these cranks on the opposite side of the shaft is the
crank to which the pushing piston is connected. The advantages of this
arrangement are that the moving masses are perfectly balanced, the
construction of the cylinder is very simple and especially adapted to high
pressures, and the reaction of the gases, instead of being directed against a
fixed part of the engine, is directed against a moving piston, thus reducing the
strain on the structure. Of course the power is not doubled or increased,
because each piston moves only half as far as it would for a given expansion
of gas were it operating in a cylinder closed by a cylinder head.
The efficiency of Diesel engines, although greater than that of the gas and
gasoline engines, is still very low. The semi-Diesel will yield about 30 per
cent of the energy in the fuel, the Junker engine about 34 per cent, and the
best Diesel, four-cycle engine in large units, about 36 per cent. This is a
wonderfully high efficiency compared with that of a locomotive, and yet it
seems pitiably low when we consider that nearly two-thirds of the energy
stored in the fuel is thrown away.

SILENCING THE NOISY EXHAUST

The waste of energy is clearly evident in the exhaust pipe of an internal
combustion engine. The gases after doing their work on the piston rush out
with such velocity as to produce a sharp explosive sound. The noise of the
exhaust is highly objectionable in automobiles and must be overcome, but
instead of utilizing the boisterous energy of the escaping gases and getting a
little more useful work out of them, means are provided for hushing their
noise. This is done by passing them through a series of baffles which reduces
the pressure of the gases before they are discharged into the atmosphere. By
letting the gases expand gradually instead of bursting suddenly into the
atmosphere the noise of the discharge is reduced. However, this must not be
done at the expense of the engine power. Unless the gases pass quickly
through the muffler they will choke and retard the exhaust and make the
engine do useless work in driving them through. Even the best of mufflers
will use up nearly 5 per cent of the engine power. The energy that escapes at
the exhaust is not the only loss. All the heat that radiates from the engine
represents just so much wasted energy. In our water and air-cooled systems
we deliberately abstract heat from the burning gases and throw it away. If we
had materials that would stand the intense heat of burning gases and enable

us to conserve all the heat developed in the cylinder we could use our fuels
much more economically.
Many attempts have been made to utilize the wasted heat of internal
combustion engines, but they have not met with any considerable degree of
success, with the exception of the invention of William Joseph Still. This
engine, which was the result of many years of patient work, was first made
public in a paper read before the Royal Society of Arts in London, May 26,
1919, and when it was shown that the new engine had developed an
efficiency of 38 to 41 per cent it was realized that here was a remarkable
advance over any other machine for turning heat into power.

COMBINED STEAM AND OIL ENGINE

The Still engine is a combined steam and gas or oil engine. The heat that
is ordinarily thrown away in the water jacket and in the exhaust is utilized to
produce steam, and this steam is employed to return the piston to the top of
the cylinder after the gases generated by the combustion of fuel have driven it
down. While in previous experiments some steam had been developed from
the exhaust gases it had not been found possible to generate steam in the
water jacket because of the low temperature that had to be maintained. In the
standard internal combustion engine the cylinder walls are made of cast iron,
thick enough to withstand the heavy pressures to which they are subjected
should the charge be ignited prematurely. Around them the water circulates
under practically no pressure and so the wall of the water jacket is made
comparatively thin. Because of the thickness of the cylinder wall the water
has to be maintained at a comparatively low temperature so as to keep the
interior of the cylinder from growing too hot. In the Still engine the cylinder
wall is from one-third to one-fourth the thickness of the standard cylinder
wall, while the water-jacket wall is of thick steel. The cylinder wall is formed
with ribs which extend to the water-jacket wall, so that the latter will take
care of any excessive loads due to premature ignition. Figure 53 shows how
the cylinder and jacket of the Still engine compare with those of the ordinary
motor. The thin cylinder wall and the ribs furnish a far better conduction of
heat to the water which circulates between the ribs. The necessary cooling of
the cylinder can be maintained with water at a much higher temperature than
in the ordinary engine.

FIG. 53.—SECTION THROUGH THE CYLINDER AND
WATER JACKET OF THE STILL ENGINE

FIG. 54.—DIAGRAMMATIC VIEW OF THE STILL ENGINE

A diagrammatic representation of a Still engine of the two-cycle heavy-
oil type is shown in Figure 54. This is shown with an auxiliary boiler heated
by an oil burner. The piston of this engine has a sleeve which fits into an
annular steam cylinder. The latter is an extension of the combustion cylinder.
Surrounding the steam and combustion cylinders are the steam and water
jackets. The drawing shows the piston at the end of its downward stroke,
having just been driven down by the gases of combustion. In this position a
scavenging-air port at the left is uncovered and the burnt gases are swept out
by a blast of air, passing out of the exhaust. This consists of a bank of tubes
or flues which pass through a water heater. The gases leave the cylinder with
a temperature of 900 degrees Fahrenheit and they issue from the exhaust with
a final temperature of only 150 degrees Fahrenheit. Steam now enters the
annular steam cylinder from the steam jacket, through the port shown at the
lower right-hand side, forcing the piston up and compressing the charge of air
in the cylinder. Then oil is sprayed in through a nozzle, not shown in the
drawing, and is ignited by the heat of the compressed air as in a Diesel engine
and the piston is driven down again by the gases of the combustion. The
water surrounding the combustion cylinder comes from the lower part of the
boiler and flows by the exhaust flues. It is maintained at a temperature of 350

degrees in the water jacket, and here is turned into steam by the heat of the
combustion. Thence it passes into the steam dome of the boiler. On the
downward stroke of the piston a slide valve, shown at the lower right-hand
side, moves down and connects the steam port with an exhaust port through
which the steam flows out into a condenser. Water from the hot well of the
condenser enters the system at the combustion exhaust. The arrows show the
course of the steam and water and the temperature at various points is given.
As may be noted there are two systems of steam and water circulation: one
from the bottom of the boiler through combustion exhaust heater to the water
jacket and back to the top of the boiler; and the other from the steam dome of
the boiler to the steam jacket, to the steam cylinder, to the steam exhaust, to
the condenser and back again from the condenser into the combustion
exhaust heater, whence it enters the boiler by way of the water jacket.

LATENT HEAT

When water turns into steam a certain amount of heat is absorbed, which
does not show in the thermometer. This is known as latent heat. If cold water
is placed in a kettle and is then heated the thermometer will gradually rise
until the water reaches the boiling point. Then there will be no further rise of
temperature, although heat is still applied to the kettle, until all the water is
turned into steam, after which the thermometer will begin to show a rise of
temperature, showing that the steam is beginning to grow sensibly hotter. In
the engine, shown in Figure 54, a boiler pressure of 120 pounds gauge
pressure is maintained, and therefore water will not boil until it reaches 350
degrees Fahrenheit. The water in the water jacket registers 350 degrees and is
therefore far hotter than it could possibly be in the open atmosphere.
However, the heat from the combustion does not raise the temperature of the
water, but expends its energy in converting the water into steam. The cylinder
wall is kept at a temperature of at least 350 degrees all the time, so that the air
that enters the cylinder gathers heat from the cylinder as well as from its own
compression, and its temperature at the end of the compression stroke is
higher than it would be in a cold cylinder, thereby insuring the ignition of the
fuel when it is sprayed in.
The Still engine can also be used as a common gasoline or gas engine of
either two or four cycle and the efficiency in such types is from 31 to 33 per
cent. This is much better than the best airplane engines, which show an
efficiency under 27 per cent. Although 41 per cent for the best Still heavy-oil

engine is a remarkable accomplishment, yet it does not begin to compare with
the efficiency of the best water turbines and Pelton wheels, which turn into
useful power from 75 to 87 per cent of the kinetic energy in the water that
drives them.

CHAPTER XI

WHEN COAL AND OIL ARE EXHAUSTED

I
N PREVIOUS chapters we have indulged in a great deal of historic
retrospect. It may be well at this point, while we are dealing with the
subject of power, to look into the future and the prospects that it holds out
to us.
It was about fifty thousand years ago, according to conservative
estimates, that primitive man first began to use tools, and he managed to exist
and thrive and develop to a very high degree of civilization during practically
the whole of that period without touching the stores of energy that lay
beneath his feet. It was only yesterday that the steam engine was invented,
and when it was discovered how to turn heat into work and what a wealth of
power was stored up in the deposits of coal there started a lavish and
profligate squandering of the precious heritage of the Carboniferous era. The
fossilized vegetation of by-gone ages is now employed to drive our
locomotives and steamships, to turn our factory wheels, to extract metals
from the ore and help us shape them according to our needs and desires, to
convert iron into steel and to heat and light our houses. We all know that
there is a limited supply of coal in the world and that some day the stores will
be exhausted, yet we go on using larger quantities of the fuel each year.
For the last century our demands for coal have been doubling every ten
years, until to-day the world is using about 1,200 million long tons per year.
It is conservatively estimated that if our demands for coal do not increase
there is enough left in the whole world within a mile of the surface to last
1,500 years. Fortunately this country is better supplied than many others, and
it is probable that we can get along on our present rations for 2,000 years.

England, however, faces exhaustion of her coal supplies within two hundred
years.
After living fifty millenniums on earth as a being clearly superior to other
animals, man comes into an inheritance which he squanders in one or at most
two millenniums. It is not creditable to our civilization that we have taken no
precautions to ration out this precious store of fuel.

OUR WASTE OF FUEL

As was shown in a previous chapter, we utilize very little of the energy in
coal. Our steam railroads squander from 94 to 96 per cent of the coal they
burn and our best turbine power plants throw away about 80 per cent. The
coal we burn in domestic furnaces is most wastefully squandered. Maybe we
shall learn how to use the energy in coal more efficiently and make it last
longer, but eventually it will all be gone and then what are we going to do?
Of the other fuels available, petroleum takes the leading place, but we are
hardly more economical in our use of this fuel and our oil supplies are
diminishing much more rapidly than the stores of coal. In 1919 the United
States produced 376,000,000 barrels of oil and consumed 418,000,000
barrels, having had to draw on Mexico for 42,000,000 barrels. Natural gas
cannot last much longer and peat bogs are estimated at about half of one per
cent of the coal supplies. Where shall we turn for heat and power when all
these stores of energy are gone?
It has been estimated that the water powers of the earth, if fully
developed, would probably supply about half of the energy that we now get
out of coal. This is a never-failing supply of energy, and no doubt before we
have begun to scrape the bottom of our coal magazines every river on earth
that is capable of turning a wheel will be doing so to the limit of its capacity.
Then there will be a readjustment of the manufacturing centers of the earth
and remote regions such as Iceland, for instance, which has more available
water power than Switzerland, will hum with machinery, while such
countries as Great Britain, which is relatively poor in water powers, will have
to give up manufacture and revert to agricultural pursuits.
But are there not other powers that can be used? If we could capture all
the energy of the winds we should have ample power to do all the work that
is now done on earth with a large margin to spare. It has been estimated that
the winds contain 5,000 times as much energy as is obtained from coal, but

how may we capture so fickle a power as the wind. It is so variable,
sometimes exerting enough power to lift houses from their foundations and
uproot giant trees, and again sinking to an absolute calm. In some places
wind power is turned into electricity and then stored up in batteries; but the
cost of doing this is high and at present uneconomical.

“BLUE COAL”

The ocean Is a vast storehouse of energy. The quiet but powerful rise and
fall of ocean tides, and the tremendous energy of ocean waves, have been
looked upon with envy by engineers. All sorts of schemes have been devised
for capturing a part of this energy and putting it into the service of man.
Water power has been aptly called “white coal” and ocean power “blue coal.”
Wave energy is but another form of wind energy and hence just as fickle.
There is plenty of power to be had, but it is a costly matter to build a power
plant on the shores of the ocean and any day a storm may arise which will
dash the machinery to pieces and sweep away the whole plant or convert it
into a pile of wreckage. In a few places, however, Nature has provided a plant
which the ocean has been unable to destroy and man has adopted the plant to
furnish him with power. There is a rocky cave on the California coast which
is exposed to the ocean swells. As the swells sweep into the cave they
compress the air therein and this compressed air is trapped in a reservoir.
Then the air that has been pumped by the ocean is put to useful work. There
are similar caves on other rocky coasts which could be made to deliver power
when coal becomes scarce and it becomes commercially practicable to
exploit them, but the amount of power they would furnish would be a mere
drop in the bucket.

SETTING TIDES TO WORK

The ocean tides are also immensely powerful, but the rise and fall of the
water is so slight and so gradual in most places that an enormous plant is
required to obtain any appreciable amount of power. In certain regions,
however, tidal power is actually in use to-day. At high tide water flows into a
large basin and at the ebb of the tide the outflow of the basin operates a water
wheel or turbine. Power can be obtained while the basin is filling as well as
while it is emptying. One serious objection to this plan is that the turbine
operates intermittently and at irregular intervals, sometimes by day and

sometimes by night, depending upon the tide. However, tide mills need not
be exposed to the fury of ocean storms as are plants that seek to employ the
power of ocean waves. In certain localities the conformation of the coast is
such as to accumulate the tidal flow and produce enormous differences of
level between ebb and flood tide. In the Bay of Fundy, for instance, the tide
rises seventy feet and an appreciable amount of power could be obtained
from the flow of water into and out of the bay. If a sea-level canal were dug
across the Isthmus of Panama there would be a flow of water back and forth
through it because the tides at the Pacific side have a rise and fall of only two
feet while on the Atlantic side the tide rises twenty-two feet. Some power
might be obtained from the tidal flow through this canal, but a fall of twenty
feet in fifty miles would not produce a very swift current.

FIG. 55.—THE ESNAULT PELTERIE PLAN OF UTILIZING TIDAL
POWER IN THE ENGLISH CHANNEL

If tidal power is to be utilized at all it must be done on a grand scale. A
French engineer, R. Esnault Pelterie, has proposed a vast tidal power system
in the English channel where the tide rises high. (See map Fig. 55.) The plan
is a most ambitious one, but the power that could be obtained is enormous.
He proposes to build concrete dikes across the channel at the Straits of Calais
inclosing a large basin about twenty miles wide and turbines would be
operated by the flow of water into and out of this basin. Of course locks
would have to be provided to permit the passage of ships through the basin.

Other and larger basins could be formed by walling off the estuary of the
Thames and the bay of the Seine on the French coast. The Gulf of St. Malo
could be inclosed by running a dike from Cape La Hague to the island of
Guernsey and thence to the mouth of the Trieux. These basins would furnish
a minimum of 800 horsepower for each square mile, hence the basin across
the Straits of Calais alone would furnish nearly half a million horsepower
while the Gulf of St. Malo would furnish about a quarter of the power that
France now uses in her industries. The first cost of the installation would be
heavy, but there would be no expense for fuel and the supply of power would
be endless. It has been proposed to dam the estuary of the Severn (England)
where the spring tides rise thirty feet, and it has been estimated that half a
million horsepower would be developed. Part of the power would be used to
pump water into an elevated reservoir which would serve as a storage battery,
so that when the tidal plant was idle because of the turn of the tide, water
flowing out of the reservoir would operate an auxiliary plant, thereby
furnishing a continuous supply of power.

POWER FROM SUNSHINE

With the exception of the tides all the energy we use on earth comes from
the sun. It is the sun’s energy that is stored in coal beds and oil fields; it is the
sun’s energy that raises water from the ocean to the tops of our mountains; it
is the sun’s energy that makes the winds blow, and through them disturbs the
surface of the ocean, and even the tides owe a part of their energy to the
attraction of the sun. Why can we not utilize the energy of the sun directly,
instead of at second hand? In the sunshine that beats upon the earth there is
seventy-thousand times as much energy as we now obtain from coal.
Unfortunately the energy of the sun is so widely dispersed that it cannot be
used economically except in a very few places where clouds do not often
interrupt the direct passage of the rays to the earth’s surface.
Near Cairo, Egypt, there is a plant erected by an American inventor, Mr.
Frank Shuman, which develops about fifty horsepower. This consists of a
series of five huge trough-shaped mirrors that focus the sun’s rays upon
boilers and thus generate low pressure steam. The mirrors measure 13 feet in
width and 304 feet in length and these are mounted on a light steel
framework with their axes running north and south so that they may be
turned from east to west to follow the course of the sun across the sky. In
order to prevent the mirrors from shading each other in the early morning and

late afternoon they are set twenty-five feet apart. Mirrors are made of thin
sheets of window glass, silvered at the back. The troughs are parabolic in
cross section and at the focus of each is hung a tubular boiler painted black to
absorb the heat rays. The five boilers feed a common steam reservoir from
which steam is fed to a pump. This pump raises about 6,000 gallons of water
per minute, which is used for irrigating purposes. Of course at night the
supply of energy is cut off and on cloudy or rainy days no steam is generated,
but such days are few in the region of Cairo, and continuous operation is not
essential to the operation of irrigating systems.
There are localities in Africa, Asia Minor, and even in the United States
where the lack of water and the pitiless rays of the sun have turned vast
regions into deserts. Here the very rays which have parched vegetation may
be utilized to pump water over the thirsty lands and convert them into rich
agricultural regions.
There is another mighty source of power in the internal heat of the earth.
Here and there all over the earth are vent holes through which the pent-up
energy makes its escape in the form of steam, gases, or molten lava. There is
no question as to the enormous stores of energy in active volcanoes, and as
we appreciate the value of heat energy our eyes turn covetously to these great
chimneys of the subterranean furnaces.

HARNESSING VOLCANOES

It seems like the height of daring to attempt to harness the volcanoes, and
yet there is a plant in Italy which utilizes volcanic energy and develops useful
power from it. At Volterra, in the province of Tuscany, there is a volcanic
region where jets of very hot steam issue from cracks in the ground. These
steam jets, known as soffioni, are laden with gases and mineral matter. For
many years the boric acid that they contain was abstracted from them, but the
steam was allowed to escape. In some few instances it was piped into houses
and used for domestic heating. In 1908 an attempt was made to convert the
energy of the steam into useful power. Holes were bored into the earth and
steam of a temperature of 302 degrees Fahrenheit came up the pipes. This
steam was applied directly to a forty horsepower steam engine, and for the
first time volcanic heat was set to work. The steam, however, contained so
many impurities that it was impracticable to use it directly in the engine. The
valves and cylinders were soon clogged with deposits of boric acid. Then

instead of trying to obtain power directly from the steam, the latter was used
to heat a boiler in which pure steam was generated. This plan proved
perfectly practical and a 300 horsepower condensing steam turbine was
driven by the energy thus obtained indirectly from volcanic heat. This power
was converted into electricity and the power was transmitted to the
surrounding villages. After the World War broke out and Italy began to feel
the shortage of fuel, the price of coal having risen to $50 per ton, the use of
volcanic power was extended. A 3,000 kilowatt plant was installed and
electric current was transmitted to Florence, Leghorn, Volterra, and other
towns of Tuscany. The exhaust steam from the boilers was utilized in the
boric acid industries.
Other projects for utilizing the internal heat of the earth have been given
serious consideration in Italy. Near Naples there is the dormant volcano,
Solfatara, the crater of which is filled with a sea of very hot mud underlying a
cool thin crust of earth. Holes bored into this mud to a depth of a few feet
send forth steam hot enough to do useful work and a plan to utilize this store
of energy is under way.

POWER FROM THE CORE OF THE EARTH

There are regions where the ground is red-hot at a depth of a hundred
feet. While there is no water present to furnish steam, it is a simple matter to
sink a water pipe down to the heated earth and then, around this pipe, to drive
a ring of smaller pipes through which steam may find its way up to the top
and be fed either into water heaters or directly into steam engines. In fact it
has been suggested that such a scheme might be used almost anywhere. If we
bore into the earth, we find that the temperature grows higher the deeper we
go. The rate of increase of temperature varies with different localities, but it
is very evident that anywhere on earth temperatures that will give a steam
pressure of ten or more pounds per square inch can be obtained if we dig
down far enough, and when we find it worth while to do so we shall probably
riddle the earth’s crust with perforations through which water will be sent
down to the subterranean furnaces and it will return to us laden with heat
energy.
After all, we shall not be plunged into dire want when our stores of coal
are exhausted. There will be other sources of power to draw upon, most of
which will be inexhaustible. Furthermore, we have recently discovered in

atoms of matter stores of energy incomparably greater than any that have
heretofore been used to work the will of man. How to utilize this energy we
have not yet learned, but the energy is there, and no doubt, some day,
probably long before coal takes its place in museum collections, we shall be
possessed of a new slave, far more powerful than that which has served us so
far.

CHAPTER XII

INVASION OF THE SEA

T
HE POSSIBILITY that the wind was the first inanimate power utilized
by man, has already been referred to. There are records of the use of
sailing vessels in Egypt that date as far back as 6,000 years before
Christ. Navigators of that early date, however, could hardly claim to
have mastered the wind. They merely used wind power when the wind was
disposed to help them. If the winds were adverse, they had no recourse other
than to furl their sail, step the mast and depend upon oars to propel them to
the desired port. It was not until thousands of years later that primitive
mariners learned how to tack and pursue a zigzag course against the wind.
When this knowledge was acquired we do not know, but it is certain that the
Phœnicians, who rounded the continent of Africa 1,200 years before Christ,
knew how to make use of the power of opposing winds. Of course they could
not explain how it was that a breeze could be made to drive a vessel in a
direction across and even opposed to that in which it was blowing. In order to
understand this apparent paradox ourselves, we must go back to the very
elements of mechanics.

ELEMENTARY MECHANICS

The popular conception of force is something that produces motion, but
its true definition is “that which tends to produce or resist motion.” There are
forces in existence when there is no motion. When you hold a weight in your
hand there is a force tending to pull the weight to the earth, but this force is
opposed by an equal force exerted by your muscles in holding up the weight.
There is no motion because the two forces are perfectly balanced. If they

were unbalanced, there would be motion in the direction of the greater force.
If the pull of the arm is greater than that of gravity, the weight will be lifted,
and if the weight is too heavy for the arm to support, it will go down despite
muscular efforts to prevent it. In one case the force of gravity will endeavor
to destroy motion by opposing the lift of the arm, and in the other case the
arm will endeavor to resist motion by opposing the pull of gravity. A book on
a table is motionless and yet it is acted upon by two forces which are opposed
to each other and hence balanced. The table furnishes a force which resists
and balances the force exerted by gravity. If the book were heavy enough, in
other words, if the force directed downward were great enough, the table
would be crushed.
When two forces are in perfect balance they must be equal and opposite.
Unless the directions of the two forces are exactly opposite, there will be
motion in some new direction. Suppose we use an apparatus such as shown in
Fig. 56 to study the result of three coacting forces. It consists of a T-shaped
frame with a pulley P at each end of the cross arm. These pulleys turn very
freely on their axes, so that we need not be concerned with any appreciable
amount of friction. Two fine cords running over these pulleys are knotted at
O to a third short cord. Each cord is provided with a hook on which weights
may be hung. Now if we put a pound weight on each cord the two A and B
will raise the weight C until the angles between the cords at O are all equal.
In other words each force of one pound is balanced by two other forces of
one pound each pulling at an angle of 120 degrees to it and to each other. If
we put a 3-pound weight at A, a 4-pound weight at B and a 5-pound weight at
C, the cords will come to rest in the position shown in Fig. 57. The weight B
being heavier than weight A will pull the knot O to the right until the angle
between the cords running to these weights is a right angle.

FIG. 56.—BALANCED FORCES—EQUAL WEIGHTS

PARALLELOGRAM OF FORCES

Although a force is something that cannot be pictured it can be
represented graphically by means of a line, letting the direction of the line
represent the direction of the force and the length of the line the strength of
the force. In Figure 58 we may measure off 3 inches from O to a to indicate
the 3-pound force and 4 inches from O to b to represent the 4-pound force
and 5 inches from O to c to represent the 5-pound force. Now if from a a line
is drawn parallel to O b and from b a line is drawn parallel to O a we shall
have a parallelogram a O b d, and if we extend the line O c it will bisect the
parallelogram, running diagonally from O to d, and this diagonal will be
found to measure exactly 5 inches which represents the 5-pound force. This is
what is known as the parallelogram of forces. It shows us the resultant of any
two forces that are not directly opposite and it gives us the direction as well
as the strength or magnitude of this resultant. It is only because we happen to
choose the forces 3, 4 and 5 that the angle at O is a right angle. In Figure 59,
where the forces are all equal, our parallelogram is lozenge-shaped and the

line O d is just as long as the line O a and O b, showing that its magnitude is
the same as that of the two forces that balanced it.

FIG. 57.—BALANCED FORCES—UNEQUAL WEIGHTS

The greater the angle between the two lifting forces the less weight can
they lift. If two men are carrying a ten-pound satchel, each will be lifting five
pounds, if the pull is directly upward; but this is a rather inconvenient way of
carrying the bag and usually they pull at a slight angle from the vertical, and
so each must carry more than half the weight. If they move so far apart that
the angle between them is more than 120 degrees, each will be carrying more
than the full weight of the bag.

FIGS. 58 AND 59.—PARALLELOGRAMS OF FORCES

SAILING AGAINST THE WIND

Now that we know something about the parallelogram of forces we may
return to the problem of sailing across and against the wind. In Fig. 60 we are
looking down on the deck of a ship and the wind is represented by the arrow.
The dotted line A B represents the direction in which the boat is traveling and
the line C D represents the plane of a sail. If the line E F represents the
magnitude and direction of the force of the wind at the center of the sail, then
we can tell how much pressure is being exerted directly against the sail, by
drawing the line g F perpendicular to the sail and completing the
parallelogram by drawing from E a line parallel to the sail intersecting g F at
G and another line parallel to g F intersecting the plane of the sail at H. Then
the length of the line G F represents the pressure against the sail. If the line G
F is half as long as the line E F, then only half of the force of the wind is
exerted in the direction G F. In other words, a wind pressure of one pound
per square foot blowing in the direction of G F will do as much work as two
pounds in the direction E F. The force of the wind has been broken up into
two “components,” one (G F) at right angles to the sail, and the other (H F)
edgewise to the plane, and of course the latter has no effect upon the
propulsion of the boat.

FIG. 60.—FORCES THAT MOVE A SAILBOAT

If there were nothing to prevent it, the boat would sail in the direction G
F; but the keel of the boat offers resistance to motion in this direction, and we
must construct another parallelogram around the force G F to find the
magnitude of the force exerted in the direction A B. The line K F is drawn at
right angles to A B, and then the parallelogram is completed by drawing a line
from G to K parallel to the line A B and another from G to M parallel to K F.
We have then resolved to force G F into two components M F and K F. The
former tends to push the boat along its course while the latter tends to make it
drift to leeward. The length of the line M F is little more than a quarter of the
length of the wind force E F and the leeward acting force K F is actually
considerably greater than the forward acting force M F. Even with a deep
keel there will be some drift to leeward. This is corrected by means of the
rudder of the ship which is turned to head the ship further into the wind so
that although the boat does not actually travel in the direction of its axis it
may be made to travel along the course A B. Of course the boat cannot sail
directly against the wind, but it can accomplish the same result by tacking
alternately to port and starboard so that eventually it can reach a port that lies
in the direction from which the wind comes.

THE SPEEDY CLIPPER

Before the advent of the steamship, sailing vessels were developed to a
high degree of efficiency. The speedy clippers of 1816 to 1845 used to cross
the Atlantic at an average speed of 6 to 9 miles per hour and sometimes even
better, which compares favorably with a common steam freighter of to-day.
The largest sailing vessel ever built was the Thomas W. Lawson, a seven-
masted schooner. She was launched in 1902, but foundered in 1907 off the
Scilly Islands. This great ship was a steel vessel 395 feet long, with a
displacement of 10,000 tons and a cargo capacity of 7,500 tons. She had a
sail spread of 40,617 feet.

FROM OARS TO PROPELLERS

Although a century has elapsed since the first steam-driven vessel made
its way across the Atlantic Ocean, sails have been as yet by no means swept
off the face of the sea. Nevertheless, even when sailing vessels had no
competitors they did not furnish a perfectly satisfactory means of
transportation. The fickleness of wind power was felt in this application as
well as in that of windmills, and inventors racked their brains for some more
certain means of propelling ships. Naturally, when the steam engine was a
proven success, efforts were made to apply this newly discovered power to
ships. How to make steam drive a ship was a problem. At first it was
proposed to use a system of oars which would be moved back and forth in
imitation of oarsmen and John Fitch’s first steamboat in 1786 was driven by a
set of paddles operated in a manner similar to that of paddling a canoe. It was
a very natural evolution from oars to paddle wheel, which consists of a series
of oars mounted in a wheel so that they will come into play one after the
other. The propeller, although not invented by Col. John Stevens (as has been
popularly supposed), was first applied by him to steam navigation when he
constructed a small steamboat on the Hudson River in 1804. But the
simplicity of the paddle wheel and its high efficiency, particularly in quiet
harbors and shallow inland waters, gave it preference over the propeller. In
rough seas, however, the paddle wheel was far from ideal. It was too easily
broken by heavy waves and between 1855 and 1865 the propeller displaced it
completely for ocean-going vessels.

WATER JET PROPULSION

Another curious form of propulsion, which dates back to the eighteenth
century and is still periodically revived by inventors, is the water jet. The idea
was to have the engine operate a pump which would drive a stream of water
out of the stern of the boat and drive the boat by reaction. The British
Government actually built two jet-propelled steamers. One of them, called
the Waterwitch, was a 1,100-ton vessel and the other, the Squirt, was a small
torpedo boat. The latter attained a speed of but twelve knots while a sister
ship of the same steam power driven by a propeller attained a speed of
seventeen knots. The Waterwitch was even less efficient. Some years ago
experimental water-jet vessels were built in New York in which a jet only ⅝
inch in diameter with a pressure of 2,500 pounds per square inch was used,
but the experiment proved a failure. The propelling force of a jet is the
reaction of the stream of water against the orifice from which it issues. The
action is just like Hero’s reaction steam turbine referred to on page 143. The
propulsion would be the same were the jet discharged in the open air or in a
vacuum or against a solid stone wall.

WATER AND AIR RESISTANCE

It takes very little power to move a boat slowly because the resistance that
has to be overcome is merely the parting of the water at the bow and closing
in of the water at the stern and the skin friction along the sides of the hull. In
addition to this there is a similar resistance offered by the air. At very low
speeds the resistances of the water and the air are practically negligible. In
perfectly quiet water with no air stirring the pull of a cord will move a ship
weighing hundreds of tons, but the motion will be very slow indeed.
Unfortunately the speed of a ship does not increase directly in proportion to
the power that drives it. Doubling the power does not double the speed. If it
takes ten horsepower to drive a vessel at a speed of ten knots it will take not 2
but 2³ or 8 times as much power to drive it at a speed of twenty knots. In
other words, the horsepower goes up as the cube of the speed. This is an
average condition for ordinary speeds. For very high speeds the horsepower
may have to be increased as the 4th and even the 5th power of the speed. The
shape of the bow and the stern is of utmost importance. The parting and
displacement of the water at the bow and the replacement at the stern produce
waves and the forming of these waves represents so much wasted energy. The
swell that is kicked up by a steamer is evidence of power uselessly expended.
Much of this loss can be overcome by careful design of the ship’s lines. A

vessel that kicks up a high bow wave—one that sails with a “bone in its
teeth”—may present a very pleasing spectacle and may seem to be traveling
at high speed, but the best designed vessel—the one that slips through the
water with no fuss—is much more economical of power. It is easy to
understand that the bow must be carefully designed to cut through the water,
but it is not so apparent that the stern must also be shaped to permit the water
to flow in readily and fill in the void behind the ship. If the stern is not
carefully shaped, there will be a serious drag on the vessel. The skin friction
of the vessel is greatly increased by fouling of the hull with marine growths.
At high speeds the wind pressure on the superstructure is considerable. Every
spar and line adds its quota. A boat that is traveling in still air at a speed of
twenty-two knots or twenty-five miles per hour is encountering the
equivalent of a twenty-five mile wind which will exert a pressure of over
three pounds per square foot of frontage.

FLYING ON WATER

Instead of cutting through the water modern speed boats are designed to
ride over it. The boats have flat bottoms which are arranged as a series of flat
planes known as hydroplanes. These planes form steps and are set at such an
angle as to make the boat rise up on the water in the same way that a kite
rises in the air. The higher the speed the higher the boat rises so that at full
speed it skims on the surface. Hence there is comparatively little power
wasted in displacing the water. Some of these boats are driven by air
propellers so that water resistance to the propeller gear is avoided. These
hydroplanes (they must not be confused with hydroaeroplanes) almost fly
over the water.

FIRST OCEAN STEAMER

It was in 1807 that Robert Fulton built the Clermont and established
steam navigation by running a regular service between New York and Albany,
and it was twelve years later that the Atlantic Ocean was first crossed by a
steam-driven vessel. It was an American vessel, the Savannah, that made the
trip. She was a 380-ton ship equipped with steam power to help her along
when the wind failed. Seventy-five tons of coal and twenty-five cords of
kindling wood were taken aboard to feed her furnace. This was thought to be
ample for the voyage, but before the trip was completed the fuel was all gone.

The log of the Savannah bears this entry the night before sighting the Irish
coast: “2 A. M. Calm. No cole to get up steam.” However the captain did
raise steam just before reaching Kinsale, Ireland, by burning wood. Watchers
ashore beholding the smoke issuing from her stack were convinced that the
vessel was afire and boats were dispatched to the rescue. The Savannah made
the trip from Savannah to Kinsale in 23 days and was under steam propulsion
for only 80 hours of this time.
Regular trans-Atlantic steam service was not inaugurated until 1838, but
for many decades steamers were equipped with sails to assist them when the
wind was favorable.
The most notable of early steamships was the Great Eastern, a combined
screw and paddle-wheel ship, 692 feet long, built in 1858. She held the
record for size until 1899 when the Oceanic, 704 feet long, was put into
service. At present the Leviathan, formerly the Vaterland, holds the record
with a length of 920 feet. It is difficult to judge of the size of a vessel out on
the open water. If the Leviathan were placed in Broadway, New York, she
would span nearly four blocks. Because of her 100-foot beam she would be
too wide to be wedged in between the skyscrapers that border lower
Broadway. If she were set up on end she would tower 158 feet above the
pinnacle of the Woolworth Building. Her power plant consists of four
turbines which total 90,000 horsepower and the huge vessel is driven at a
speed of 25.8 knots or nearly thirty miles per hour.
The wonder of these huge floating structures lies not merely in their
gigantic proportions but in the fact that they are able to weather the terrific
wrenching strains of heavy ocean storms. A skyscraper is built to withstand
only the steady and direct pull of gravity and the variable thrust of the wind
which, except in western cyclones, seldom amounts to thirty pounds per
square foot. Bridge building is more difficult because of the leverage of the
parts overhanging the foundations. Wind pressures must be calculated and
also the live load of objects moving over the structure. In naval architecture
enter the problems of building construction combined with those of bridge
building, complicated by the fact that there is no fixed foundation for the
structure to rest upon. At one moment a ship may be spanning a trough in the
seas and at the next it may be seesawing over the crest of the wave. Of course
the bottom of the boat is seldom if ever out of the water and a certain amount
of support is provided throughout the length of the vessel, but the ship is
subjected to the strains of a cantilever bridge when she is passing over a

wave, and to the strains of a truss bridge when spanning a wave trough.
These strains are increased by the fact that the structure is in constant motion.
A certain degree of flexibility is demanded of the materials which go into the
structure and of the joints between the frame members.

BOATS OF ARTIFICIAL STONE

Originally wood was used for the hulls of ships; then between 1845 and
1855 iron supplanted wood, Between 1875 and 1885 steel supplanted iron
and to-day efforts are being made to supplant steel with concrete. The
advantages offered by concrete are cheapness and speed of construction. The
first large vessel built of this material was the Faith, an 8,000-ton ship. This
boat stood up very well in heavy weather despite the rigidity of her structure.
It is doubtful, however, that a large boat comparable in size to the Leviathan
could weather a severe ocean storm.
The proposal to build ships of cement created almost as much of a
popular sensation as did the first iron boat. Although the public had accepted
iron and then steel as a perfectly proper material for shipbuilding, concrete
seemed too much like stone and it did not seem possible that artificial stone
could be made to float. They did not realize that a cubic foot of steel weighs
four times as much as the same volume of concrete. Of course concrete does
not begin to have the tensile strength of steel and consequently the walls of a
concrete ship must be made relatively thick. For this reason a concrete vessel
is heavier than a steel vessel. She draws more water and requires a larger
power plant, and because of her greater mass she is not so readily
maneuvered.

SUBMARINE NAVIGATION

As was explained in Chapter VI, a body will float only so long as it is
lighter than the volume of water it displaces. It is almost impossible to keep a
body suspended in water unless some portion of it is exposed above the
surface. If it starts sinking it will keep on going down until it reaches the
bottom of the sea. There is a popular notion that at great depths water
becomes dense enough to float solid iron, but water is practically
incompressible and its density at a depth of five miles is only slightly greater
than that at the surface. An object must therefore either float on the surface or

sink to the bottom, unless its weight is exactly equal to the difference
between the upward pressure of the water under it and the downward
pressure of the water above it. Such an ideal balance it is practically
impossible to obtain unless the object itself is compressible.
How then can a submarine navigate under water without sinking to the
bottom?

A SUBMARINE OF THE SEVENTEENTH CENTURY

The first solution to this problem dates back to the seventeenth century.
Doctor Cornelius Van Drebel, a Netherlander, who was a guest at the court of
King James I of England, built three submarines between 1620 and 1624.
These were rowboats covered over with a water-tight deck and propelled by
twelve oarsmen. It is recorded that Van Drebel discovered a means of holding
the boats submerged by observing some fishermen towing baskets full of fish
up the Thames. The barks to which the baskets were attached by cables were
weighted down by the load they were towing, but when the cables slackened
the boats rose a little bit. Van Drebel’s method of applying this principle was
evidently to attach a weight to the boat which trailed along the bottom. When
the oarsmen propelled the boat, she was pulled down under the surface by the
drag, but when the rowing ceased the boat would float up to the surface. King
James himself is said to have made a journey of several hours’ duration in
one these boats, which was kept at a depth of twelve to fifteen feet below the
surface. Progress must have been very slow because the range of the
submarine was given as five or six miles.
During the Revolutionary War David Bushnell built a submarine with
which attempts were made to sink a British frigate lying in the Hudson River.
This submarine was driven by a hand-operated screw propeller. The boat was
provided with water ballast tanks, and by pressing a valve with one foot he
could let in water enough to submerge the boat while with the other foot he
could operate a pump to empty the tanks and bring the boat to the surface.
When the boat was ballasted so that she would barely float, a vertical screw
propeller was operated to raise or lower her as much as desired. A 200-pound
lead weight was attached to a long cable which passed up through the bottom
of the boat, and by letting out this cable the submarine could be made to rise
instantly in case of an accident.

FULTON’S HAND-PROPELLED SUBMARINE

To Robert Fulton, however, belongs the credit of building the first
submarine operating on the principle that is now universally used. His boat
was also driven by a hand-operated screw propeller and was furnished with
water tanks which could be filled or pumped out at will, but after the
submarine was weighted until only the conning tower showed above water,
she was submerged or raised by means of horizontal rudders or hydroplanes
which could be tilted to any angle desired. Of course these rudders, like any
other rudders, would not operate unless the boat were in motion. Such is the
case with modern submarines. Like bicycles, they must keep on going or they
will fall. If they are heavy, they will fall to the bottom, and if light they will
“fall” to the surface. When in motion the hydroplanes will either hold them
down or lift them up according to the angle to which these horizontal rudders
are tipped.
Robert Fulton’s Nautilus had a fish-shaped hull of copper plating on iron
ribs and was twenty-one feet three inches long by six feet five inches at her
greatest diameter. The screw propeller was operated by two men. When the
boat was on the surface a sail was raised to assist in driving the boat. This sail
could be folded up like a fan when it was desired to submerge.
Fulton deserves full credit for anticipating so many of the essential
features of the modern submarine, but of course the Nautilus was a mere toy
compared to the marvelous machines which swim under the surface of the
sea to-day.
The German U-boats at the outbreak of the war were 150 feet long and
could make only nine knots submerged and twelve knots on the surface, but
later they grew to a length of 300 feet with a submerged speed of twelve
knots and a surface speed of eighteen knots. The British in the meantime
developed a submarine that was 340 feet long and had a displacement
submerged of 2,700 tons as against 800 for the largest German U-boats. The
speed of this big British boat is twenty-four knots on the surface and ten
knots submerged.

SUBMARINES AS SURFACE BOATS

Despite their name, submarines are really surface boats. Only when
necessity demands are they submerged. During the war even the U-boats did

90 per cent of their sailing on the surface. Origially submarines were built
primarily for submerged travel and consequently they were given the form of
a fish or of a fat cigar, but such a shape was not adapted for surface sailing.
Water piled up on the nose of the boat and tended to bear her down. To
overcome this, submarines are now shaped more like a boat with a bow high
enough to part the waves without burrowing into them.

POWER PLANT OF A SUBMARINE

The gasoline engines that were formerly used for propelling the boats
have now given way to heavy oil or Diesel engines, because of the greater
efficiency of these engines and the greater safety of handling heavy oil. Some
submarines have been equipped with steam power plants. Such is the power
used on the big British submarines above referred to. Of course any power
that involves the burning of fuel can only be used on the surface. As has
already been explained, an internal combustion engine burns seven to nine
times as much air as oil and it would be impossible to store enough air on
board to keep the engines going very long; hence they can be operated only
while the hatches are open to the atmosphere.
Coupled to the shafts of the engines are dynamos which generate
electricity and feed it to storage batteries. A dynamo will serve as a generator
when turned by some mechanical power and on the other hand when current
is fed into it, it serves as a motor, so that when traveling submerged and fuel
can no longer be used, the generators are disconnected from the engines but
remain connected to the propeller shafts and driven by the very current they
previously stored in the batteries.

THE COLLAPSIBLE “EYE” OF THE SUBMARINE

Amidships there is a bridge from which the vessel can be navigated when
on the surface and a conning tower from which she can be navigated when
running awash. Most of the submerged travel is maintained at a
comparatively shallow depth so that the submarine can keep an “eye” on the
surface. The eye is the periscope of which there are two so that in case of
damage to one the other may be used. Periscopes date back to the “Fifties”
when they were used on some experimental European submarines. In the
Civil War, when the river monitor Osage ran aground in the Red River, her

captain, now Rear-Admiral Thomas O. Selfridge, rigged up a periscope with
which he could look over the high banks of the river and direct the fire of his
guns upon a Confederate force that was attacking him. This periscope
consisted merely of a three-inch pipe with a hole at each end cut in opposite
sides of the pipe. Small mirrors were set in the pipe so that the light coming
in through the upper hole was reflected down through the pipe and out of the
lower hole. This crude periscope is the same in principle as the modern
submarine periscopes except that the latter are provided with lenses to gather
and focus all the light possible on the eyepiece so that the operator will have
a perfectly clear view. Periscopes extend fifteen to twenty feet above the roof
of the conning tower. While periscopes are insignificant objects on the broad
seas when a submarine is moving very slowly, they are made conspicuous by
the wake of foam that follows them when the boat is traveling even at a
moderate speed. For this reason during the war the Germans developed a
telescoping periscope which could be shot up to the surface whenever desired
in order to give the commander a glimpse of his surroundings.
The submarine is submerged by letting water into the ballast tanks and
then turning the hydroplanes to a diving angle. There is an after as well as a
forward pair of diving rudders.
When running completely submerged the submarine is blind and solely
dependent upon the chart and compass. It is impossible to see far under
water. Searchlights are of no value at all. They will not make visible an object
a hundred feet away. The submarine commander cannot see even the bow of
the boat he is piloting. The ordinary magnetic compass will not operate when
entirely incased in steel as it is in the hull of the submarine and so a
gyroscope compass has to be used instead.
While the compass serves as a guide for travel in the horizontal plane the
depth gauge must be watched to see that the boat does not dive too deeply.
The pressure of the sea increases at the rate of 64 pounds per foot of depth.
Two hundred feet below the surface the pressure amounts to about six tons on
every square foot of the surface of the submarine. Few submarines can stand
a greater pressure than that without being crushed or at least springing serious
leaks. When coming to the surface the hydroplanes are used and if the boat is
to remain on the surface water is blown out of the ballast tanks.

THE “EARS” OF A SUBMARINE

Although submarines may be blind under water they are not deaf. Sound
detectors are used which enable them to locate other vessels by the throbbing
of their engines or the beat of their propellers and so they can avoid collisions
when coming up to the surface.
Despite the perfection of the submarine the sea is still a great mystery to
us. We know only its surface and its shallows. We have sounded a few deep
holes and brought up samples of deep-sea life, but we have not been able to
penetrate in person its profound depths and explore with our eyes and hands
the world that is buried beneath its waves. Three quarters of the globe is
covered by water and if we are to claim complete mastery of the earth we
must find some way of descending into the heart of the ocean and exploring
its deepest valleys.

CHAPTER XIII

SLIDING, ROLLING, WALKING, AND CREEPING

I
N ALL forms of transportation friction plays a most important part. If
there were no such thing as friction, it would be impossible for us to set
an object in motion by the means that are now commonly in use, and
once the object were moving it would be impossible to stop it except by
bringing it up against a wall set squarely across its path.
In transportation on land friction is a much more serious bar to motion
than it is in marine or aerial transportation. There are two kinds of friction
that we have to contend with; sliding friction when two contacting surfaces
are dragged by each other; and rolling friction when one surface rolls upon
another. It is impossible to obtain two surfaces that are absolutely smooth;
there are minute elevations in each that sink into minute depressions of the
other like intermeshing teeth and a grinding action takes place as these
microscopic inequalities are broken away. Oil reduces the friction by filling
up these inequalities, but the oil itself offers a certain amount of friction just
as water does along the sides of a moving ship.

ROLLING FRICTION

Rolling friction is of a different kind. The intermeshing inequalities or
microscopic teeth are lifted out of contact with, one another just as the teeth
of gear wheels are carried out of mesh. But there is another cause of friction
due to the fact that no objects are so microscopic that they do not sink into
each other to some extent. A wheel is always rolling out the surface it is
turning on just as a rolling pin rolls out dough. If the surface is of elastic
material such as a steel rail, it springs back into place immediately after the

passage of the wheel, but the wheel must constantly travel in the trough of a
wave which accompanies it along the rail. There is a similar wave in the
wheel itself and this ironing-out action produces heat in the wheel and the
rail. It is particularly noticeable in the flexible tires of automobiles which,
after a run on even a smooth road, become too hot to be grasped with the bare
hand merely because of the waves of compression and decompression to
which they are subjected.
Both rolling and sliding friction are increased by pressure because the
depression is greater and because inequalities are brought into more intimate
engagement with one another. The degree of friction also depends upon the
nature of the substances in contact, but theoretically the area of contact does
not make any difference. It is just as hard to push a block along a smooth
surface on its edge as on its side.

PUTTING ROLLERS BETWEEN LOAD AND ROAD

As intimated in Chapter I the forerunner of the wheel was probably the
roller. It was much easier to move a heavy object on rollers because rolling
friction was substituted for sliding friction, but the rollers would not stay
under the object; they traveled only half as fast as the load they carried. To
make them keep up with the load they had to be mounted on axles which
were fastened either directly to the load or to a cart body on which the load
was supported. Thus the wheel came to be invented, but except for the fact
that it stays by its load and does not roll out from under it a common wheel is
not to be compared with a roller for efficiency. To be sure, it substitutes
rolling friction for sliding friction where it contacts with the road, but the
friction at the axle is sliding rather than rolling. However, drawing an object
on wheels is a decided improvement over sliding it along the road, for two
reasons: the sliding friction at the axle is reduced to a minimum by choosing
materials that will slide upon each other with comparatively little resistance,
by polishing them smooth and by lubricating them. But even if these
precautions were not taken there would be a distinct advantage in the use of
wheels because of the relatively shorter travel at the axle than at the rim of
the wheel. If a wheel is thirty inches in diameter and turns on an axle one
inch in diameter, it will travel thirty times as far at the rim as it does at the
axle; hence the sliding friction at the axle is far less than it would be at the
point of contact with the ground, were the wheel locked so that it could not
turn. But it is not necessary to have any sliding friction at the axle if we

revert to the old roller system that prevailed before the day of the wheel. The
axle may be considered the load and the axle bearing the road. We can then
put rollers between load and road. Because the road is a circular one that
travels with the load we can line it with rollers throughout its length, and the
load will never lack for rollers to roll upon. Thus we have the roller bearing
which is so widely used in modern vehicles. Ball bearings operate on the
same principle except that the balls furnish less contacting surface and are not
so suitable for supporting heavy loads, as are rollers. Sliding friction is
almost completely eliminated and unless heavily loaded a wheel on ball
bearings will not heat even when the bearings are not lubricated.

REDUCING ROAD FRICTION

While there is little friction between a wheel and the roadway upon which
it travels, the roughness of the road is a very important factor. Every time a
wheel goes over a stone the entire vehicle must be lifted; this represents so
much wasted energy. The advantage of the pneumatic tire lies in the fact that
it absorbs small inequalities without making it necessary for the entire
vehicle to rise over them. This means less load lifted and hence less work
done. Large wheels are better than small ones because they do not sink so
deeply into depressions and because they surmount small obstacles more
readily. On a steel track the size of the wheel does not make so much
difference as it does on a road because the track surface is smooth and is but
little depressed by the wheel. It has been estimated that a horse can pull ten
times as great a load on rails as on an ordinary macadamed road. Some years
ago broad steel tracks were laid in some of our city streets for the use of
horse-drawn trucks. They served very well as far as the vehicles were
concerned. The road friction was reduced considerably, but the fact was
overlooked that the horses needed a good friction surface under their feet.
Two horses could not pull a truck along the track without walking on the
track and the smooth steel made such slippery footing that the tracks had to
be torn out and replaced with common paving.

INCREASING TRACK FRICTION

The difference between sliding and rolling friction is well illustrated in a
locomotive. The driving wheels are turned around by steam power. They
must either roll or slide on the track and the load they will pull without

slipping is a measure of the excess of sliding friction over rolling friction. To
increase the traction or the adhesion of the locomotive to the track it is
provided with a number of driving wheels. In some of our largest
locomotives driving wheels are placed under the tender so as to obtain a
maximum of traction.

ANCIENT LINEAGE OF THE AUTOMOBILE

When it was first proposed to substitute steam propulsion for the horse it
was not realized that a rail would furnish enough traction to permit of hauling
heavy loads, and some of the early locomotives that ran on rails were
provided with toothed wheels that engaged in racks alongside the rails. In
fact, the earliest locomotives were not built to run on rails but on ordinary
roads; in other words, they were automobiles. The motor car can therefore
boast of a more ancient lineage than the railroad engine. Joseph Cugnot of
France is said to have built a three-wheeled steam carriage in 1769 which was
so top-heavy that it upset when making a sharp turn at three miles per hour.
Several steam carriages were built in England in the eighteenth century, but
they were not successful. The real father of steam traction was Richard
Trevithic, of Camborne, Cornwall, whose first steam carriage, built in 1801,
carried eight passengers. His third machine, built in 1804, was the first to run
on rails. This was strictly a locomotive intended to haul cars. It ran with its
load at the astonishing speed of five miles an hour. Trevithic was the first to
exhaust the steam from the cylinders into the smoke-stack and thereby
increase the draft through the furnace and generated steam at higher pressure.
All the early locomotives used toothed gears to turn the driving wheels
until George Stephenson introduced connecting rods to drive the driving
wheels direct from the pistons. George Stephenson’s “Rocket,” built in 1829,
won a prize of 500 pounds in a speed contest when it established a record of
24 1-6 miles per hour. It also established the doubtful honor of being the first
mechanical speed monster to exact the toll of human life. On its prize run it
ran over a man and killed him.

STEPHENSON’S LINK MOTION

FIG. 61.—STEPHENSON’S LINK MOTION

Stephenson’s son Robert is commonly credited with the invention of an
ingenious link motion, although the invention is also claimed for W. T. James
of New York. We must pause a moment for a description of this ingenious
link motion, because it became a standard in locomotive construction that is
still in service. As explained in Chapter IX steam should be used expansively
in order to obtain a maximum of efficiency. After a certain amount of steam
has been admitted into the cylinder it is cut off from the boiler and it pushes
the piston by its own expansion. The speed of the locomotive must be varied
by varying the point of cut-off, and the direction of motion of the locomotive
is reversed by reversing the motion of the valve. In the Stephenson link
motion this is all effected by the operation of a single lever. Fig. 61 shows the
arrangement. The valve is moved back and forth by the rod A which is
connected to the arm B suspended from the frame of the locomotive. The
drive shaft is shown at C and it carries two eccentrics projecting on opposite
sides of the shaft which move the rods D and E back and forth. The outer
ends of these rods are connected to opposite ends of a curved link F and a pin
G on the arm B engages a slot in the link. The link is held up by a rod H. As
the drive shaft rotates the slotted link is oscillated back and forth on its own
center. When the link is lowered so that the pin G is at the center of the slot

there is no motion of the valve rod A, but when the pin is at the top or at the
bottom of the slot the valve rod has its greatest motion. As the top of the link
is moving in one direction while the bottom is moving in the other direction,
it will be plain that the action of the valve when G is at the top of the link will
be the reverse of the action when G is at the bottom. The link is raised and
lowered by means of a lever I which is connected to one arm of a T-shaped
lever J which on one side of its fulcrum is connected to the rod H and on the
other to the counterweight K.
There are certain defects in the Stephenson link motion that we cannot
discuss here. These became serious as engines grew larger and more powerful
so that to-day it has been largely superseded by other valve gears. The most
important of these is the Walschaerts gear, invented by a Belgian engineer.
This gear, unlike Stephenson’s, is conspicuously placed outside the drivers
and is particularly noticeable because of its peculiar grasshopper motion. The
action of the gear is so complicated that a description of it would be out of
place in this book.

MODERN LOCOMOTIVES

We cannot enter minutely into the development of the locomotive from
the crude machine of Trevithic’s time to monsters of to-day. There has been a
progressive growth of locomotives in power and in speed. Our biggest freight
engines are so powerful that they cannot be used for pulling alone because
they can pull a greater load than the draw-bars of the cars can stand. If placed
at the head of a long train they would yank the forward cars loose from the
rest. Hence they are placed at the rear of the train to act as pushers or in the
middle of the train where half their energy is expended in pushing the cars
ahead of them and the other half in pulling the rest of the train.
The most powerful steam locomotive of to-day (1921) weighs 342 tons
and its tender 107 making a total of 449 tons. Its length is 105 feet and its
boiler 8 feet 7⅛ inches in diameter. Its low pressure cylinders (4 feet in
diameter) are larger than the locomotive boilers of 50 years ago. Its high
pressure cylinders are 30 inches in diameter and the stroke is 32 inches. It
may be operated either compound or simple, i. e., the smaller cylinders may
exhaust into the larger ones or they may take steam direct from the boiler.
The tractive effort compound is 147,200 pounds and simple 176,600 pounds
and the total horsepower developed is 5,040. Each cylinder drives five

coupled drivers, in other words there are twenty power-driven wheels with a
pair of trailers and a pair of pilot wheels. Six and a half tons of coal are
consumed per hour.
In the matter of speed a mile per minute has become common and regular
scheduled runs over long distances at an average well above sixty miles per
hour have been maintained, but the present tendency is to reduce speed
somewhat in favor of safety.
There are two inventions that have made possible the high speeds of
modern railroad travel: the air brake, which has already been described; and
the block signal system. The latter, of which there are a number of different
types, being electrical, does not properly belong in this book.
Stoking a large freight engine or a high speed passenger locomotive is
strenuous work. Three tons of coal per hour is not an uncommon rate of
consumption. The fireman on a fast express train gets little rest. To relieve
him of this exhaustive work automatic stokers are now being used. These
convey the coal from the tender to the fire box and feed the fuel at a uniform
rate. In place of solid fuel, oil is extensively used in regions where it may
readily be obtained. This simplifies the task of firing the locomotives. There
has also been some use of powdered coal which is blown into the furnace in
much the same way as oil is.
To-day steam locomotives have found a serious competitor in the electric
locomotive, which is steadily increasing in favor.
Where traffic is heavy, where long tunnels make the smoke and gases of a
steam locomotive dangerous, where electric power is plentiful, the steam
locomotive must give place to electricity. As the cost of coal mounts, the
electrification of railroads will spread and it will be only a matter of time
before the electric locomotive, which is far more economical in its use of
power, will completely supplant the steam locomotive.

FIRST AUTOMOBILE ACCIDENT

As we have already noted, the automobile antedated the railway
locomotive. It was an accident that took the primitive steam carriage off the
high roads and put it on rails. In 1802 Richard Trevithic, while speeding
along a road at the frightful speed of ten miles per hour, lost control of his
machine, ran into a fence and ripped off a number of palings. That accident
spelled the doom of the early automobile. So dangerous a machine was not

allowed to run at large. Special tolls and restrictions were placed on power-
driven road vehicles. As late as 1896 when the automobile had become a
practical machine in France and was being rapidly developed in this country,
England still had a law prohibiting any power-propelled vehicle to travel over
the highways at a higher speed than four miles per hour and required further
that the vehicle be preceded by a man bearing a red flag.
The most important early American road car was that built by Richard
Dudgeon in 1855, which made a record speed of forty miles per hour. In 1889
Serpollet, in France, invented the flash boiler and interest in steam-driven
automobiles was revived. In a flash boiler water is turned into steam as it is
used by injecting small quantities at a time in a red-hot tube. In the meantime,
however, the internal combustion engine was being developed. Lenoir, in
France, was the first to build a motor car driven by an internal combustion
engine. He obtained a patent on such a vehicle in 1860. However, the real
father of the modern automobile was Gottlieb Daimler of Germany, who
patented a motor vehicle in 1884 driven by an internal combustion engine.
The next year Karl Benz, another German, built an automobile.

AMERICAN PIONEERS OF THE MOTOR CAR

Pioneer work in this country began with Charles E. Duryea in 1891. Five
years later he took one of his machines to England, where it entered a fifty-
two-mile race between London and Brighton. There were many entrants from
France, Germany, and other European countries. The American car won the
race by nearly an hour over its nearest competitor. Commercial building of
automobiles began in America in 1894. However, it was not until the opening
of the twentieth century that America took hold of the motor car in real
earnest. Since then the rise of the automobile industry has been phenomenal.
American methods of manufacture were applied and cars were turned out in
quantity. In 1916 the annual production exceeded a million and to-day the
production is about two million passenger cars and over three hundred
thousand trucks. The motor car industry is largely responsible for the
wonderful progress in American machine tools that has been made in the past
two decades.
On the race track the motor car has established a record speed of 131
miles per hour, but of greater utility has been the motor truck which now
competes with railroads in the transportation of freight. Owing to New York’s

inadequate terminal facilities, it takes less time to haul a load from New York
to Philadelphia by motor truck than to take the same load from the
warehouse, transport it across the Hudson River, and load it on a freight car.
It has made the country a part of the city. A short run brings the farmer’s
produce to the markets and his passenger car keeps him in close touch with
city life. The motor tractor has lightened his work on the farm and has
enabled him to conduct farming operations over vast areas. Animal power is
gradually giving way to mechanical power. This, however, is a special branch
of automotive engineering which we must look into.

WHEELS VS. LEGS

The success of the automobile depends upon the character of the roads it
has to traverse. Wheels provide the best form of transportation over a smooth,
hard road, but if the road is soft, the wheel will sink into the surface and will
be greatly impeded. In traveling over mud or sand runners are preferable to
wheels because they have a broader and longer bearing surface. In the snowy
regions of the north and the sandy regions of Africa and Asia Minor, sledges
are used in place of wheeled vehicles. Sliding friction is less than rolling
friction under such conditions. In fact, only where man has constructed
special roads is it possible to use wheeled locomotion. It is because in nature
we must contend with all sorts of surface conditions, soft and hard and
seldom smooth, that the rolling principle of locomotion is not to be found in
any species of animal. The legs of an animal are levers, just as a wheel is a
system of levers, but in the former case the levers can be folded or extended
to adapt themselves to all the unevennesses of the ground. No animal can
begin to run as fast as an automobile on a good road, but on the other hand
we have yet to build a machine which will run as fast as a horse on soft and
uneven ground.

WALKING MACHINES

Farm operations must be conducted on loose and broken surfaces for
which the ordinary wheeled vehicle is unfitted. In some cases broad wheels
are used to keep them from sinking into the soil and they are furnished with
cleats so as to give them a good grip on the ground, but long ago it was
realized that if the horse was to be completely displaced on the farm a more
adaptable form of locomotion than that of wheels must be furnished.

Inventors sought to make machines that would walk. One interesting machine
of this class which met with a certain degree of success attempted to combine
walking and rolling. Large wheels were used which were provided with a
series of feet or tread plates connected by knuckle joints to the wheel rims. As
the wheels revolved, these treads came successively into contact with the
ground and the machine actually walked on its feet. The feet were broad
enough to prevent the machine from sinking into the ground and they adapted
themselves to inequalities in the surface. Instead of having to roll over a rock
that lay in its path the machine would plant its feet on the rock and lift itself
over.
A very curious machine of the walking type has been developed for
excavating machines that operate in soft swampy ground. The machine
actually walks over surfaces that a light carriage could not negotiate. It
consists of a large central turntable flanked on each side by a pair of broad
and long tread plates which serve as feet. When the dredge is to be moved, it
plants the feet on the ground, lifts up the turntable, moves it forward, and sets
it down again; then the feet are lifted, moved forward, and planted on the
ground again while the turntable is moved forward again. When it is desired
to make a turn the machine is swiveled around to the desired direction while
sitting on the turntable with its feet raised clear of the ground. Of course the
speed of such a machine is very low, but transportation is of secondary
consideration. The main purpose of the machine is to excavate ditches in soft
ground and only occasionally does it have to move its position. The turntable
provides a broad base that distributes the load over a comparatively large area
which prevents the machine from sinking into the mud, and if it should sink
into a soft spot it lifts itself out vertically instead of having to roll out.

“CATERPILLAR” TRACTION

Long ago it occurred to inventors that a machine could travel over
trackless wastes if they carried their own tracks with them. The idea dates
back more than a century, but only in comparatively recent times has it been
developed to a practical stage. The track-laying mechanism takes different
forms, but in one prominent type it consists of a series of plates linked
together to form a chain or belt that passes around a series of wheels. As the
machine progresses the plates are successively laid down in front of the
wheels and picked up behind them. The wheels consist of a large number of
rollers whose axles are spring-supported so that they are capable of a certain

amount of vertical movement and as the belt they roll upon is made up of
separate plates they can adjust themselves to irregularities of the ground and
creep over an uneven surface. Its close resemblance to the creeping
locomotion of a caterpillar has led to the adoption of the trade name
“caterpillar” by one of the large tractor manufacturers. The tractor belt is
driven by spur wheels at each end and the rollers serve merely to distribute
the weight of the machine along the belt. The traction is exceedingly great
because the belt is broad and long, giving it a large gripping surface. For the
same reason it will not sink into plowed ground. Because of its flexible tread
surface it will creep over rocks and stumps, waddle down into a ditch and
climb up the opposite bank. So powerful is it that it will crash through
underbrush with ease and even small trees yield before it. It will run over soft
mud, deep sand, and even snow with equal facility. The tread belts on either
side of the tractor are separately driven and by making one belt run faster
than the other it is possible to steer the machine. In fact it can be made to turn
around in its own length by stopping the belt on one side and driving the belt
on the other.
Such a machine is ideal for plowing and other are hauled with ease over
the soft plowed ground. For ordinary farming purposes speed is not essential,
but the possibility of rapid travel with tread-belt traction was demonstrated in
the World War when small “tanks” were built which could run at the rate of
twelve miles per hour.

CHAPTER XIV

INVASION OF THE SKY

F
ROM the day when man began to assert his superiority over other
animals he began to cast longing eyes at the sky. Fired with ambition
and stirred with a spirit of mastery he chafed at the bonds that bound
him to earth; but the heavens remained a forbidden kingdom to him.
Many a bold adventurer who dared to emulate the birds paid the penalty of
his temerity with a broken limb and even with his life. It seemed as if man
were destined forever to grovel on the bed of the atmospheric ocean with
never a chance to rise except in dreams and fancy.
It was not until near the close of the eighteenth century that a means of
rising off the earth was discovered. Two brothers, Stephen and Joseph
Montgolfier, of Annonay, France, were sitting before a fire, watching the
smoke curl up the chimney, when it occurred to one of them that smoke
might serve as a vehicle to carry them up into the air. They belonged to a
prominent paper-manufacturing family and naturally turned to that material
as the most suitable for trapping and harnessing the smoke. They began their
experiments with a large bag of thin paper which they filled with smoke and
floated up to the ceiling. The next step was to fasten a dish filled with
burning embers to the bag, so that the balloon carried its own smoke
generator. The experiment was tried in the open air and the balloon arose to a
great height. Larger bags were made of linen and paper and on the fifth clay
of June, 1782, a public exhibition was given. A pit was dug in the ground in
which a fire was lighted and over this was placed a huge balloon which
weighed 300 pounds. Eight men were required to hold it down while it was
filling with heated air and, when released, it shot up to an elevation of about
6,000 feet and came to earth about a mile and a half away.

THE FIRST HYDROGEN BALLOON

When the news of this event reached Paris a professor of physics named
Charles suggested that hydrogen, being much lighter than air, would raise the
balloon without the use of fire. By a popular subscription funds were raised
to defray the expenses of securing enough iron filings and sulphuric acid to
generate the hydrogen necessary to fill a balloon of 22,000 cubic-foot
capacity. On the 27th of August, 1783, a flight was attempted. The big bag
arose without mishap and disappeared in the clouds. Three quarters of an
hour later it landed in a field fifteen miles away much to the astonishment of
the villagers thereabout who gathered around the strange bobbing monster
with mingled fear and curiosity. One of the number, more daring than the
rest, advanced and shot the balloon, whereupon the crowd closed in and tore
it to pieces with their pitchforks.
In November of the same year the Montgolfier brothers built a balloon 48
feet in diameter and 74 feet high, and Jean François Pilatre de Rozier, a
professor of natural history, made several ascents with the balloon held
captive. Then, in company with the Marquis d’Arlandes, the balloon was cut
loose and the balloon voyage was undertaken. Below the car of the balloon
was an iron vessel in which a fire was maintained to furnish the heated air.
The aeronauts each carried a bundle of fuel to feed the fire and a wet sponge
to extinguish sparks that might ignite the bag. Despite this precaution a
number of holes were burnt in the envelope, but nevertheless the flight was
successful and the daring voyagers came to earth without mishap after a short
journey.
M. de Rozier’s career as an aeronaut was a short one. The first man to be
carried up in a balloon, he was also the first balloon victim. He undertook to
combine the Montgolfier and the Charles systems by building a balloon that
employed both the hot air and the hydrogen principles, but the balloon took
fire and De Rozier with his companion, the Marquis de Maisonfort, were
both killed. Two months after De Rozier’s first balloon ascension a flight was
made at Lyons in a huge fire balloon which carried seven passengers. This
big bag was 100 feet in diameter and 130 feet high, with a capacity of
590,000 cubic feet. The invasion of the air was now well under way, although
for a time it made little real progress. Owing to the danger of fire, hot air
eventually gave way to hydrogen and later to coal gas, which, although it did

not have half the lifting power of hydrogen, possessed the advantage of being
much cheaper.

THE WEIGHT OF AIR

It seems hardly necessary in this day and generation to explain that a
balloon rises because it is lighter than the air it displaces, but it does seem
astonishing that a balloon weighing several tons may yet be lighter than an
equal volume of air. We do not ordinarily think of air as having any weight.
We know that the ocean of air bears on the earth with a pressure of about 14½
pounds per square inch, or about a ton per square foot at sea level. This
amounts to 28 millions tons per square mile and, when we multiply this
figure by the number of square miles of surface in the total area of the earth,
we find that the whole ocean of air has a weight of 5,500,000,000,000,000
tons—a figure which is far beyond our conception, but it does impress us
with the fact that air is a ponderable substance. Of course, the atmosphere
that exerts a pressure of 14½ pounds per square inch is scores of miles deep,
but even a small quantity of air has appreciable weight. If weighed in a
vacuum a cubic foot of air would tip the scales at 1¼ ounces, and 100 cubic
feet would weigh close to 8 pounds. The air in an empty room 10 feet square
and with a 10-foot ceiling weighs nearly 80 pounds at a temperature of 32
degrees Fahrenheit. In other words, if we had a box measuring 10 feet on
each side and weighing less than 80 pounds in a vacuum it would float in the
atmosphere when the thermometer was down to the freezing point, provided
there was no air in the box to weigh it down.
Vacuum balloons were proposed long before the time of the Montgolfier,
but the problem was to construct a vessel strong enough to resist the crushing
pressure of the atmosphere. The best bracing for the walls of the vessel is
some gas dense enough to exert a pressure equal to that of the atmosphere but
whose weight is less than that of the air. The weight of the vessel must then
not exceed the difference between the weight of the gas and an equal volume
of air. The Montgolfier brothers used heated air to keep their box or envelope
distended. Air expanded by heat is lighter than cold air. However, it does not
make a very good filler because 1,000 cubic feet of air heated to 212 degrees
Fahrenheit weighs 59 pounds, leaving only 21 pounds on a freezing cold day
for the absolute weight of our 1,000-cubic-foot box. Coal gas, on the other
hand, weighs about 40 pounds per 1,000 cubic feet at 32 degrees Fahrenheit,
while the same volume of hydrogen weighs only 5½ pounds. If coal gas were

used to brace our box against the pressure of the air we should have a surplus
of about 40 pounds for the weight of the box, while hydrogen would allow us
74½ pounds. Of course, the weight of a volume of gas depends upon its
density. No matter how small a weight of gas we placed in the box it would
fill the box completely, but when we speak of a 1,000 cubic feet of gas or
hydrogen we mean a volume sufficiently dense to bear against the container
with the same pressure that the atmosphere presses outside; i. e., 14½ pounds
per square inch. Temperature also affects the pressure. In the case of fire
balloons the hot air inside the envelope is less dense and hence lighter than
cool air outside, but the pressure is equal because the former is expanded by
heat. The volume of gas in a hydrogen or coal-gas balloon varies greatly with
the temperature to which it is subjected. For instance, if on rising through a
cloud or a blanket of fog, the balloon should encounter the rays of the sun,
the heat would burst open the envelope were no vent provided. The mouth of
the bag is kept open, however, for just such emergencies so that the surplus
gas may escape. On the other hand, sudden chilling of the gas will contract it
and send it down to earth, or the balloon might encounter a downward current
of air, when the only salvation of the aeronaut is to throw out the ballast.

BALLOON NAVIGATION

Balloons seem like very helpless craft, and yet they are capable of skillful
navigation at the hands of an experienced pilot. Although the balloonist has
no means of self-propulsion and must drift with the winds, he is capable of
controlling motion in the vertical direction and can choose the particular air
currents on which he desires to ride. By throwing out sand ballast the bag
may be made to rise and by letting out the gas it may be made to descend,
and a pilot who is familiar with prevailing currents of the atmosphere or able
to interpret meteorological indications, may locate the air stream that will
carry him to his destination. Sand is the balloonist’s fuel; when that is gone
the balloon may as well come to earth at once. Its course can no longer be
directed and there is nothing to prevent it from being suddenly dashed to
earth should it run into an “air hole,” which is another name for a downward
air current. When a balloon comes to earth it is liable to be dragged by the
wind and many accidents from dragging occurred in the early days of
aeronautics until John Wise, an American, invented the rip panel by which
the envelope may be ripped open by pulling a cord, thus freeing the gas and
permitting the bag to collapse instantly.

A LOOM PROVIDED WITH A JACQUARD ATTACHMENT
Note the belt of cards that determine the pattern that is to be woven

A BATTERY OF MULE-SPINNING FRAMES

JACQUARD ATTACHMENT FOR LOOMS

SEVEN MILES ABOVE THE EARTH

The greatest altitude ever attained by a balloon has been claimed for
Glaisher and Coxwell, who in 1862 went up to a height of seven miles. Both
men were overcome by the extreme rarity of the atmosphere. Coxwell,
however, although nearly paralyzed and unable to move his arms, succeeded
in seizing the safety valve rope in his teeth and pulled it before he lost
consciousness. The balloon was then at an altitude of 29,000 feet and rising at
the rate of 1,000 feet per minute. Thirteen minutes elapsed before he regained
his senses, and then the balloon was falling at the rate of 2,000 feet per
minute. From the data furnished, it has been estimated that an altitude of
37,000 feet was reached. While there has been much dispute as to the
authenticity of this record, the altitude of 35,100 feet established in 1901 by
Professor Berson and Dr. Suring in the German balloon Preussen, probably
represents a higher ascent than that of Glaisher’s balloon.
The new system of aerial transportation proved very useful in the
nineteenth century. During the siege of Paris, in 1870-1871, sixty-six
balloons arose out of the beleaguered city, and all but seven made their
escape in safety. In our own Civil War captive balloons were first used to
direct the fire of artillery. It was in one of these balloons that Friedrich von
Zeppelin, who was a German military attaché with the Union forces, made
his first aerial ascent. He was so impressed with the advantages of military
observation from such a lofty aerie that he became from that moment an
aeronautical enthusiast, and on his return to Germany urged upon the military
authorities the importance of the balloon in war. It was then that he began his
aeronautic studies and experiments which culminated in the construction of
the gigantic ships of the air with which Germany undertook to carry the terror
of war into England.

KITE BALLOONS

In the World War captive balloons were extensively used by both sides,
an important development being the kite balloon. The common spherical
captive balloon is very unsteady except in perfectly still air. It bobs around
and swings and turns, making an unfavorable base for careful observation. In
heavy winds it is liable to be dashed to earth by sudden gusts. The kite
balloon is held up not only by its own buoyancy, but also by the wind in the

same way that a kite is supported. The bag is elongated (sausage-shaped) and
is fastened to the anchor line in such a way that it is tilted like a kite. To assist
in holding it in this position the balloon is ballasted at the after end and the
ballast, if you please, is air. A big air-filled bag hangs from the stern of the
balloon and serves as a rudder while two other horizontal bags serve as
stabilizing fins.

SELF-PROPELLED BALLOONS

No sooner had the Montgolfier brothers proved that it was possible to rise
off the earth upon a bubble of hot air, than inventors began to devise schemes
of propelling the bubble and controlling its course. The first dirigible balloon
was built in 1784 and, strangely enough, oars were used to propel it. The
balloon had a fish-shaped body, just like that of modern airships, and the bag
was kept inflated by means of air as it is to-day. It was realized even at that
early date that the envelope must retain its shape if it is to plow through the
air with a minimum of friction. As the gas would gradually leak out of the
envelope the bag would become flabby and present a crumpled bow to the
ocean of the air and, to overcome this, a double envelope was provided and
air was introduced between the inner and outer skin. Means were provided
for pumping air in as the gas slowly escaped, thus keeping the envelope fully
inflated. As the air was pumped in sand ballast was thrown overboard so that
the buoyancy of the airship was not impaired. To-day air is used to keep gas
envelopes inflated, but instead of placing the air in an outside envelope it is
introduced into a small bag inside called a “ballonet.”
From time to time other means of propulsion were proposed and tried. In
1852 Henri Giffard, who is known as the Fulton of aerial navigation, built
and operated a dirigible driven by a steam engine, which he hung at a
considerable distance below the gas bag, so that the fire box would not be
liable to ignite the highly inflammable gas. A draft was maintained in the fire
box as it is in a locomotive by letting the steam discharge into the smoke
stack, but in this case the stack was inverted and the smoke and gases were
blown downward and away from the coal gas with which the balloon was
inflated. The danger of fire and the difficulty of building a power plant light
enough to be carried aloft and powerful enough to give the craft any material
headway were the chief obstacles that had to be overcome. At the close of the
nineteenth century, Santos Dumont, a Brazilian inventor, built a balloon that
was driven by a gasoline engine. Despite the apprehension of other aeronauts

this machine proved an unqualified success. Two years later, in 1900, Count
Zeppelin introduced the rigid dirigible, which to-day is the standard for large
airships.

THREE TYPES OF DIRIGIBLES

There are three types of dirigible airships; the flexible, the semirigid, and
the rigid. In the flexible type, as we have observed, the envelope must be kept
tightly filled in order to hold its shape when driven against the air. The car is
suspended from the gas bag. In the semirigid type a rigid frame or backbone
serves as a keel for the gasbag and helps to prevent it from crumpling up. In
the rigid type a casing incloses the gas or rather bags; for the gas Is contained
in a number of separate bags fitted into separate compartments. The casing is
composed of a framework of duralumin, which is an alloy of aluminum, with
a percentage of copper and nickel. It weighs but little more than aluminum,
but is five times as strong. Over the duralumin framework is stretched a
sheathing of rubberized fabric. Because of the weight of this casing rigid
dirigibles must be made in large size.

ACROSS THE ATLANTIC IN A DIRIGIBLE

Before the war large Zeppelins were built that were fitted with luxurious
cabins and dining rooms and made regular scheduled voyages. The big
British dirigibles are of the Zeppelin type. The R-34, was 672 feet long and
79 feet in diameter. It was fitted with nineteen gas bags and had a total
capacity of over two million cubic feet of hydrogen. It was driven by five
engines, each developing from 250 to 275 horsepower, and was capable of
making from 50 to 75 miles per hour, depending upon whether or not the
engines were pushed. The big dirigible left the Royal Naval Air Station, near
Edinburgh, on the 2d of July, 1919, and landed at the Roosevelt Field near
Mineola on the 6th, having made the trip in four days and two hours. The
course covered about 3,100 sea miles, but the actual air mileage was about
6,300 miles because head winds were encountered. In aeronautic voyages it is
the distance through the air that must be reckoned rather than the distance
over the ground or sea. An airship may be traveling at the rate of 50 miles per
hour through the air, but if there is a wind of 30 miles per hour blowing
against the course of the dirigible, the latter will be making only 20 miles per
hour over the ground, or if the wind is blowing with the airship it will be

making 80 miles per hour over the ground. Because of the head winds the
transatlantic flight of the R-34 was so much longer than had been anticipated
that its stores of fuel were almost completely exhausted. And yet, when the
airship started out from Edinburgh, it carried 81 tanks of gasoline, each
containing nearly 70 gallons, or a total of 4,900 gallons. This fuel weighed
nearly 16 tons. Almost a ton of oil and 3 tons of water added to the load and
the baggage and crew amounted to 4 tons more. The total weight carried was
over 24 tons and the dirigible fully loaded weighed altogether about 60 tons.
When the dirigible started out it had to fly low, but as the fuel was consumed
it grew lighter and rose higher. The surplus hydrogen had to be pumped into
steel tanks where, owing to its compression, it was heavy and served as
ballast which could at any time be fed back into the gas bags to increase the
buoyancy of the airship. We can no longer think of air as having no weight
when we consider that all this tonnage was supported by air.
The R-34 was by no means the largest dirigible built, but we dare not
boast of the size of the airships of to-day when the aeronautics is in its in-
fancy, because our present dirigibles may seem puny alongside the big
aircraft that may be built to-morrow. The dimensions of the R-34 have been
given because of the historic interest in this first dirigible to span the Atlantic
Ocean.

HEAVIER-THAN-AIR MACHINES

Marvelous as was the achievement of the Montgolfiers and wonderful as
were the aeronautic developments that followed the invention of the balloon,
the dominion of the birds was not really conquered until man had learned
how to fly in a machine heavier than the air. Captive aeroplanes date back to
the remote ages of ancient history. Kites are really “heavier-than-air
machines.” They maintain themselves in the air because they travel through
the air at a considerable velocity. True, a kite may be stationary, or practically
so with respect to the ground, but if we detach ourselves from the ground and
view the situation from a drifting balloon, the earth will appear to be moving
under us and the kite will rush past us as it is dragged by the earth to which it
is tied. The idea of propelling a kite through the air, not by tying it to the
earth, but by furnishing it with its own propeller and power plant, was
conceived long ago, but the problem was to find a power plant light enough.
The honor of being the first man to rise off the ground in an aeroplane
belongs to C. Ader, who made several short flights between 1890 and 1896 in

a machine driven by a twenty-horsepower steam engine. Our own S. P.
Langley did some most important pioneer work in flying and built a man-
lifting, steam-driven machine in 1903 which would have flown had it not
been for an accident to its launching gear. In fact, this very model was flown
successfully a number of years later. However, it was not until the gasoline
engine was developed that the power plant problem was solved. The internal-
combustion motor was made more and more powerful in proportion to its
weight until now there are several types that weigh less than two pounds per
horsepower.
But the power plant was only one obstacle to be overcome. The real
problem was to learn how to control the machine after it rose into the air.
Otto Lilienthal attempted to learn how to fly in a motorless flying machine.
He provided himself with wings and, jumping off a height or running down a
slope, depended upon gravity to furnish him with the necessary propulsion
through the air. Unfortunately after five years of gliding experiments a fatal
accident terminated his aeronautic research.

THE WRIGHT BROTHERS

In this country the Wright brothers, Orville and Wilbur, took up the work
of Lilienthal and they, too, undertook to learn to fly before they built a flying
machine. In all his years of experiment, Lilienthal did not have more than
five hours of experience in the air. The Wright brothers determined to spend
more time in the air and less in theoretical speculations at home, so they built
a gliding machine that would sustain a man at a speed of eighteen miles per
hour and picked out a spot on the Atlantic coast where they were assured of
fairly constant winds of sixteen to twenty-five miles per hour. At first the
machine was used as a kite and various experiments were made in balancing
it. Then short gliding flights were made from the tops of the sand dunes. Not
until the art of balancing the glider and controlling it in unsteady air currents
was any attempt made at building a motor-driven flying machine. It was by
these experiments that the Wright brothers discovered the system of warping
the wings so as to preserve the lateral balance of the machine. After several
seasons of experimental gliding, and not until they felt that they had learned
how to fly, was a power machine built. This made its first flight on December
17, 1903. The first flight lasted only twelve seconds, while the fourth flight
lasted fifty-nine seconds. Many months were spent in perfecting the machine
and in solving the various problems of flight, and not until September, 1905,

did the Wright brothers feel that they had mastered the art of flying. After that
three years elapsed before the world was actually convinced of the reality of
airplane flight and recognized the work of the pioneers.

TRANSATLANTIC AEROPLANE FLIGHTS

The development of the heavier-than-air machine is so recent and is still
advancing so rapidly that we dare not give more than a brief outline of its
progress here. The more important advances are familiar to most of us and a
record of achievements to-day will be hopelessly out of date to-morrow. The
war gave a tremendous impetus to flying. Pilots were trained by the thousand.
Machines grew in speed up to 150 miles per hour. Huge bombing machines
were built, with a wing spread of over 125 feet, and weighing ten to fifteen
tons. These were capable of carrying a load of four to five tons. The first
flight across the Atlantic was made in June, 1919, by the United States navy
flying boat NC-4, which flew to Newfoundland, then to the Azores, and from
there to Lisbon, Portugal. The trip was finally completed by a flight to
Plymouth, England.
The first nonstop flight was made in the same month by a Vickers Vimy
bomber which, with a favoring wind of thirty miles per hour, made the trip in
less than eighteen hours at a rate of 120 miles per hour. To-day all-metal
aeroplanes are being flown successfully. Plans are under way to build
aeroplanes for service at extremely high altitudes, where greater speeds are
possible owing to the tenuity of the air and the consequent lowering of head
resistance. These machines are to have inclosed bodies in which air at normal
pressure will be maintained by means of blowers. The blowers would also
furnish the engines with air necessary for proper combustion of the fuel.
We are not going to give a history of the progress of aviation since the
invention of the Wright biplane, but instead we shall look briefly and in a
very elementary way into the principles underlying the flight of heavier-than-
air machines.

WHY A KITE STAYS UP

What is it that makes a plane or a kite stay in the air? The answer is
inertia. The balloon shows us that air possesses weight; the aeroplane shows
us that air possesses inertia. This is a natural consequence. Every body

possesses inertia and the heavier the body the greater its inertia. By inertia we
mean resistance to change of motion or rest. The pressure of air against the
face of a fan is due to its resistance to a change from state of rest to a state of
motion, while the pressure of wind against a surface represents the resistance
of air in motion to being brought to a state of rest. The more sudden the
change the higher is the resistance or pressure developed. If an open
newspaper be laid over one half of a ruler, while the other half extends
beyond the edge of the table, the ruler may be broken by a sharp blow on the
overhanging end, not because the other end is held down by the weight of the
newspaper, but because the inertia of the air bearing on the broad area of the
paper prevents the ruler under the paper from rising in response to the sudden
blow at the overhanging end. It is the inertia of the air, i. e., its resistance to
rapid displacement that keeps a parachute from falling like a solid shot to
earth.
Figure 62 shows how a kite is maintained in the air. The line AB
represents the plane of the kite, the line CO at right angles to this plane is the
pressure against the center of the kite surface. The wind pressure DO is
resisted by the pull of the kite string and exerts a lift EO, which resists the
vertical pull of gravity. The sum of the forces DO and EO must be equal to
the force CO. If EO is greater than the force of gravity the kite will rise, and
if it is less the kite will fall. The magnitude of the force EO depends upon the
velocity of the wind DO and the angle of the kite AB to the wind. If the plane
of the kite were parallel to the direction of the wind the angle would be zero
and the lift would also be zero.

FORCES THAT SUPPORT AN AEROPLANE

FIG. 62.—FORCES WHICH HOLD UP A KITE

In an aeroplane conditions are just the same as in a kite, except that a
propeller drives the plane through the air with a force equal to CO. The plane
is slightly curved, so that air which is deflected or forced down at the forward
edge will continue to press against the plane all the way to the rear edge. The
shape of the top of the plane is also important. As the plane is driven through
the air a partial vacuum is formed above the plane, so that the difference in
pressure between the two sides is increased and there is a greater lifting
effect. This partial vacuum is known as “cavitation.” In the early days of the
aeroplane it was not realized how important was the effect of cavitation on
rapidly moving objects. Every spar and member of the airplane as it plows
through the air builds up a head resistance in front and is followed by a wake
of rarefied air unless it is given a stream-line construction. This is illustrated
in Figure 63, which shows at the left a rectangular body traveling through the
air and at the right a stream-lined body. The flow of the air is indicated by the
lines and it is evident that head resistance and cavitation are reduced by
forming the body with a bulging bow and tapering stern. To-day all the
exposed parts of aeroplanes are stream-lined as far as possible. In the early
Wright machines wire braces were extensively used. It was not supposed that
a wire would offer much resistance to the air, but, upon investigation, it was

found that the wire braces would vibrate laterally and present virtually a
broad surface which materially increased the head resistance.

FIG. 63.—FLOW OF AIR AROUND A RECTANGULAR BODY
AND A STREAM-LINED BODY

The angle of the plane determines to a large extent the head resistance of
the plane. If the plane is horizontal the head resistance is at a minimum, but
the lift is also very slight. If the wing planes were perfectly flat, there would
be no lift at all, but because of the curve of the wings there is a certain
amount of lift when they are horizontal, and even when they are tipped
slightly downward, provided the machine is traveling at high speed. The
angle of an aeroplane’s wings is therefore much flatter than that of a kite.

MAINTAINING THE EQUILIBRIUM OF AN AEROPLANE

In order to maintain itself in equilibrium the center of gravity must
coincide with the center of pressure, otherwise there will be a turning action
about the center of gravity and the machine will upset. The location of the
center of pressure depends upon the angle of the plane. The greater the angle
the farther it is from the forward edge of the plane and the pilot can maintain
fore-and-aft equilibrium by tilting the horizontal planes of his rudder so as to
change the angle of the machine, and hence of the main or forward planes.
Unfortunately the air is a turbulent ocean filled with invisible air currents and
the aeroplane must be capable of adjustment to meet the variations of
pressure due to sudden gusts of wind. This is particularly true of lateral
balance. A gust coming from the side will put a greater pressure on one side
of the aeroplane than on the other. To meet this the angle of the plane at one
side must be less than that at the other. This was discovered by the Wright
brothers and their method of overcoming the lateral variations of pressure
was the key to their early success. They warped their wings or twisted them

so that the angle of the wing was reduced on the side from which the gust
came and was increased on the other, and thus the center of pressure over the
whole wing was kept on the line of the center of gravity. At the same time
there was a variation in head resistance which had to be corrected by moving
the rudder, and the Wright brothers used a single lever to warp the wings and
at the same time to operate the rudder so as to keep the aeroplane on its
course.
Before the Wright brothers made public their invention other aeronauts
had great difficulty in making turns. When turning, one side naturally has to
move through the air faster than the other. This produces an increase of
pressure on one side over the other which may be counterbalanced by
warping the wings. The same effect is produced by the use of small wing
planes, called “ailerons,” at each side of the main planes. An automatic means
of stabilizing an aeroplane has also been devised, a description of which will
be found in Chapter XXI.

CHAPTER XV

HELPING THE FARMER

T
HE FIRST efforts at directing the forces of nature and employing
them in the service of man were made by the farmer. The task of
growing food was quite the most important of primitive occupations,
and although the virgin soil was rich and the yield abundant there
were regions where crops could not be raised except at the expense of
constant toil. Infrequent rains made it necessary to carry water by hand
from wells and rivers and pour it over thirsty lands. As the grain fields grew
more extensive, irrigating ditches were used which saved the toil of
carrying the water, although it still had to be raised by hand. Then machines
were invented by which water could be raised by animal power and, finally,
as we have already seen, automatic water-lifting machines were constructed
by which the river itself was constrained to lift a part of itself and pour this
part into the irrigation ditches.
While it is true that the earliest machines were built to lighten the work
of the farmer, the attention of inventors was soon attracted to other fields of
endeavor and the farmer was left to toil slavishly from daybreak to
sundown with no further mechanical aid. The tools he used were improved
in form and quality. Oxen were used to draw the plow. The wooden plow
made out of a forked stick gave way to a bronze plow and, finally, to one of
iron. The curved knife or sickle went through a similar process of evolution
from flint to iron. It was the only implement used for cutting the standing
grain, and not until comparatively recent times did it give way to the scythe.
Practically all the work of tilling, seeding, cultivating, harvesting and
threshing was done by hand in practically the same way and with

practically the same tools from the time of the Pharaohs down to the end of
the eighteenth century.

THE FIRST HARVESTING MACHINE

To be sure, there is a record of a harvesting machine built in Gaul, while
that province was under Roman dominion. Pliny described this machine in
70 A. D. It consisted of an ox cart which was pushed through a field of
grain, instead of being pulled by the ox. This cart carried a rack or comb
which caught the heads of the standing grain, tearing them off and
delivering them into the body of the cart. Unfortunately this primitive, but
useful, harvester was not extensively employed and in time it was lost to
agriculture. Farmers reverted to the time-honored method of reaping by
hand and the ox-pushed machine was forgotten. From time to time in recent
years this machine has been reinvented and a machine similar in principle is
used to-day to gather clover seed.
The scythe was a distinct improvement over the sickle. It enabled a man
to use two hands at the work of reaping instead of one. It provided a much
longer and heavier blade, and hence a much broader swath was cut at each
stroke. A distinctly American improvement on the scythe is the grain cradle,
consisting of a set of fingers above the blade which catch the grain and lay
it in a swath at the end of the stroke. This important improvement rapidly
spread to all parts of the world and is still used to-day where it is
impracticable to use a mechanical reaper. It is claimed that one man can cut
and bind more grain with the cradle than three men could with the sickle.

EVOLUTION OF THE PLOW

The plow has undergone important developments in comparatively
recent years. Wooden plows were still in use in America in Revolutionary
times; usually the point was shod with wrought iron. However, these
wooden plows speedily gave way to metal when iron came to be
manufactured in considerable quantity in this country. A plow has to
contend with two conditions of service that apparently conflict with each
other. The constant friction of the soil against the blade tends to wear it
away very rapidly, hence a very hard surface is requisite. On the other hand,
the plow is apt to encounter buried stones and rocks which will shatter it

unless it is soft. The problem then is to make the plow both hard and soft.
The chilled iron plow was invented by Oliver, in 1855, to meet the first
condition. When molten iron is poured into an iron mold the surface that
comes into contact with the mold is suddenly chilled, producing a very hard
surface that takes a good polish. This effect is accentuated by using a
hollow mold through which water is circulated. The hard surface of the
chilled iron wears well in sandy and gravelly soil, it does not rust deeply,
and it clears well in sticky soil. However, it is very brittle and is liable to
break if struck a sharp blow. A more recent improvement is the soft-center
steel plow. This is both hard and soft. It is composed of three layers of
metal; the outer layers are of hard cast steel and the center one of soft steel.
These metal layers are heated to a welding heat and then rolled together,
producing a plow that has a hard outer wearing surface and at the same time
is tough because the center layer of soft steel acts as a cushion to absorb
sharp blows. To increase the wearing qualities of the plow still further a
patch of very hard cast steel is welded over the point of the share. Thus both
conflicting requirements of softness and extreme hardness are met.
We think of the plow as a very simple tool, but the modern implement is
a product resulting from a vast amount of study and research into the
materials most suitable for its construction and into the best form of share
and moldboard. In place of a single plow for all purposes the modern
farmer is offered a large assortment to suit various classes of work. At least
three different kinds of plows are indispensable on every farm; the sod
plow, the stubble plow, and the corn-cultivating plow. The sod plow is used
for turning over the sod and breaking the clod. This is provided with a
jointer or diminutive plow point set above the share, which turns over the
edge of the furrow to prevent grass from growing up between the furrows.
The stubble plow has a moldboard with less twist than that of the sod plow.
This is used for plowing land that was under cultivation during the previous
year.
The plow of to-day has become more than a hand-guided, horse-drawn
tool. It has developed into a real machine, mounted on wheels, with a disk
or coulter wheel that cuts the furrow cleanly, means for leveling the plow
and regulating the depth of the plow, and a seat for the plowman. It works
upon soil with the same precision that a planer works upon a slab of cast
iron. The furrow is neatly sliced, lifted, and turned over with mechanical
accuracy. As the furrow slice slides over the moldboard of the plow the soil

is pulverized by friction. The front furrow wheel runs in the furrow
previously cut which serves as a track to guide the machine. The front and
rear furrow wheels are inclined from the vertical so as to balance the thrust
of the plow and they may be given a lead toward or from the “land” or
unplowed part of the ground to regulate the steering automatically. The
proper adjustment and balancing of a plow calls for considerable skill.
Agricultural operations are now conducted on such a vast scale that the
single plow cannot begin to do the necessary work. Instead, sets of gang
plows are used so that from a dozen to two dozen furrows may be turned at
a time. Steam or gasoline tractors of the wheel or track-laying type are
required to furnish the tractive effort needed to haul these huge plows. The
larger tractors are so powerful that they haul not only the plow but a harrow
behind the plow to break up the clods and a seeder behind the harrow to
sow and cover the seed so that all three operations are performed
simultaneously.
The disk type of plow is used in very dry and hard soil and also in very
sticky soil. A rolling disk takes the place of the moldboard and share, and in
this way friction is reduced very materially, with the result that less tractive
effort is required to draw the machine.
There is scarcely any agricultural operation for which a machine has not
been designed. We cannot attempt to describe them all. For tilling the soil
there are plows, harrows, drags, and rollers of many different varieties; for
seeding and planting there are grain and seed drills, corn planters, potato
planters, etc.; for cultivating or working the growing crops there are
cultivators, weeders, fertilizer drills, corn plows, etc.; and for harvesting or
gathering the crops there are mowers, hay rakes and tedders, reapers and
binders, potato diggers, corn binders and huskers, corn shellers, etc.

INVENTION OF THE REAPER

Most interesting of all are the reapers because they represent the first
successful efforts to introduce machinery into farming operations. Toward
the close of the eighteenth century the Royal Agricultural Society of
England offered a prize for the invention of a successful reaper, which
stimulated inventive effort in this field. But although many patents on
reaping machines were granted by the British patent office, nothing was

produced that completely met the requirements. In fact even as late as 1851
when a World’s Fair was held in London the British had no really successful
reaper to exhibit. In the meantime, American inventors had been at work
and two inventors in particular, Obed Hussey of Maryland and Cyrus
McCormick of Virginia, had developed machines which had so far proved
their worth that they were extensively used on American farms. These two
inventors, working independently, produced machines that were very
similar in basic principles. As our patent regulations of that period did not
call for an extensive search of the prior art there was no official
investigation to show which was entitled to the honor of priority of basic
principles or whether both did not include in their applications much that
was old. Hussey filed his patent on the last day of 1833 and McCormick in
June of 1834.
The main stumblingblocks of earlier inventors of reaping and mowing
machines was in finding a suitable method of cutting the grain. Revolving
combs for tearing off the heads of grain, fingers for gathering the grain and
holding it against a revolving cutter, horizontally reciprocating knives—all
these methods were tried without success. Nearly three years before Hussey
obtained his patent, Manning, of Plainfield, New Jersey, solved the problem
by inventing a reciprocating cutter with spear-shaped blades cooperating
with a finger bar that guided and held the grain against the blades. This
invention was apparently unknown to either Hussey or McCormick and
their patents show cutting means that were broadly the same as that of
Manning.

THE “FULTON” OF AGRICULTURAL MACHINERY

Of the two rivals, McCormick showed the better business ability in
perfecting his invention and promoting it so that he eventually became to be
considered the “Fulton” of agricultural machinery and the public forgot the
pioneer work of Hussey. As a matter of fact, McCormick built his first
successful reaper three years before he obtained his patent. Four horses
were hitched to the machine and he went out into a neighboring field of oats
to demonstrate it. In less than half a day he had reaped six acres, which was
a remarkable performance when we consider that a single acre was
considered a day’s work for one man. McCormick’s machine had a reel
above the cutter to hold the grain against the knife and as the grain was cut

it dropped upon a platform. A man walked alongside the machine and
removed the grain with a rake. And so the reaper with two men to operate it
did the work that had formerly required twelve men with the cradle.
The next important improvement was to provide a seat at one side of the
reaper so that the man with the rake could ride. While this reduced the labor
of the man it did not materially increase the efficiency of the machine. The
next step, however, was of material importance. In place of raking off the
hay by hand an automatic rake was furnished and the services of the extra
man were dispensed with. One man could then do the work of twelve.
McCormick had had difficulty in introducing his machine into public use,
but now its superiority over hand labor was so marked that reapers came to
be extensively employed on American farms. The reaper had reached this
stage of its development when the World’s Fair of 1851 was held in London
and McCormick’s machine was sent across the Atlantic to be displayed at
the exhibition. At the same time Hussey sent over one of his machines
which had reached the same stage of development. There was a British
machine also on exhibition based on the invention of Rev. Patrick Bell of
Scotland in 1826, but in a competition with the American machines it could
not begin to compare in efficiency. The work of the American machines was
a revelation to the British farmers. The prize was carried off by
McCormick’s machine, which was declared by the judges to be worth the
whole cost of the exposition. Unfortunately Hussey was not on hand to
direct the operation of his machine, which may have had something to do
with its failure, for in another test the Hussey reaper was found superior to
the McCormick.
The excellence of American reapers was now well established and their
fame spread throughout Europe. In a competitive test held near Paris in
1855, America won the highest honors by cutting an acre of oats in twenty-
two minutes as against sixty-six minutes for a British machine and seventy-
two for an Algerian machine. In 1878 McCormick was made a member of
the French Academy of Sciences in honor of his achievements.

TYING KNOTS BY MACHINE

After the self-raker was introduced the next important improvement was
in the binding of the grain. At first the cut grain was raked into a receptacle
which was dumped by the driver of the machine when enough had

accumulated to form a bundle and the bundles were bound by men
following the machine. As in the evolution of the raker, the next step was to
provide a platform for these men on the machine so that they could ride as
they bound the grain and finally in 1873 a self-binding attachment was
invented which increased the efficiency of the machine manifold. This self-
binder, however, called for the use of wire which did not meet with favor as
a binding material because of the difficulty of cutting it without a special
tool. Efforts were therefore made to introduce twine instead. But twine
cannot be fastened by mere twisting; it has to be tied and a mechanical
means of tying a knot was far from an easy problem to solve. While it is
true that the human body is a machine and every movement of which it is
capable may be reproduced by mechanical means, the difficulty is to copy
many operations without involving such complexity of members as to make
the mechanism wholly impracticable. The human hand is really a very
intricate piece of mechanism which by long generations of evolution and
development has become wonderfully deft. It exhibits this deftness and
complexity of movement in tying knots and the very intricacy of this
operation was enough to baffle the majority of inventors. There was one
inventor, however, who was not to be thwarted even by so formidable an
obstacle as this. In 1864 Jacob Behel secured a patent on an attachment for
binders which would actually tie a knot. The mechanism passed the twine
around the gavel of grain, formed a loop in the two ends, and tied a simple
overhand knot in much the same way that the hand ties this knot. Ten years
later Marquis L. Gorham improved the mechanism and built a successful
twine binder. Finally in 1879 John F. Appleby perfected the binding
mechanism, completing the last stage in the development of the modern
automatic self-binding reaper.
To keep pace with the reaper, other agricultural machines had to be
invented and developed. The vast quantity of grain harvested could not be
threshed by hand and the old-fashioned flail had to give way to the steam-
driven threshing machine. Finally to meet the requirements of the vast
western wheat fields, the combined harvester and thresher was developed
which, with a crew of four men, will reap, thresh, and bag between two and
three thousand bushels per day. According to statistics of the U. S.
Department of Agriculture it took a man three hours and a half to produce a
bushel of wheat in 1830 as against ten minutes in 1896. Surely the world
owes a tremendous debt to Hussey and particularly to McCormick for

introducing machinery into agriculture and starting the train of inventions
which in the space of two-thirds of a century have led up to the present
remarkable era of machine farming.
There still remains one task of the farmer that has not yet been
accomplished with unqualified success by machine. The harvesting of the
corn crop is a tedious and disagreeable task and one which the farmer
would only too gladly turn over to the machine. To be sure, many corn-
harvesting machines have been built and put into service with more or less
success, but none has reached the perfection of other classes of agricultural
machinery. The difficulty lies not in the machine, but in the fact that corn is
so easily beaten down by storms that at harvest time the machine seldom
finds the stalks all standing up in nice straight rows. Machines must
therefore be provided with means for lifting up the fallen stalks to vertical
position. The stalks are cut and bound into bundles and stood up in shocks.
Even more difficult than cutting and binding is the task of husking the
corn. This work was always dreaded by farm hands, but now machines are
provided to husk the ears and shred the stalks for fodder. Thus the farm is
being relieved of its drudgery. Unfortunately it is only the large western
farms that can afford to avail themselves of the latest agricultural
machinery. On small eastern farms it does not pay to purchase a machine
which can be used for only a few weeks in the year and then must be stored
away until the next season, but small farmers are now cooperating and
clubbing together to buy the less frequently used machines and so even the
small farm is being relieved of its drudgery, and the arduous burdens which
have always had a tendency to drive young men away from the farm are
now being assumed by the unfeeling machine.

CHAPTER XVI

MACHINING THE EARTH

T
HE ALBANIAN people have a story that the Creator recently visited
the earth and was astonished to find how it had changed. “Why, this is
not the earth I created,” He said. “Everything has changed. My forests
are cut down; My rivers have been diverted from their courses; My
hills have been blasted away, and My mountains have been robbed of their
minerals. The whole face of the earth has been altered.” But in the course of
His roamings, the Creator suddenly came upon the land of Albania. “Ah!” He
exclaimed in delight. “Here is a bit of earth untouched by man. It is still just
as I made it.”
Man’s ambition to make over the face of the earth to his own liking dates
far back of the present age of machinery. However, the work of the ancient
engineer was accomplished only at the expense of decades and generations of
hard manual labor. To-day, with powerful and gigantic machinery to do our
bidding, we do not hesitate to change the course of rivers, to level off the
hills, to carve highways through the mountains and pierce them with tunnels,
to bore into their depths for treasure and drive deep holes into the bowels of
the earth in quest of liquid fuel. We are able to machine the earth in much the
same way as a piece of metal is machined in the machine shop. In fact, the
drill, the circular saw, the slotter, and even the milling machine have their
counterpart in the excavating machinery of to-day. Of course we cannot
expect to find the counterpart of such machines as the lathe, boring mill, and
planer, in which the work revolves against the tool, because this planet of
ours is rather too big a piece of stock to be placed between lathe centers or to
be bolted to a planer bed.

MECHANICAL MONSTERS

The twentieth century finds this planet again stocked with monsters larger
and more powerful than the gigantic saurians that dominated the earth in the
Jurassic and Cretaceous epochs, but our mighty fire-breathing, steel-sinewed
beasts are humbly subservient to the will of man.
The spectacle of a large steam shovel at work makes one feel at once very
small and very big. Before the work of this monster the human shoveler
shrinks to the proportions of a mere insect. Seven to eight cubic yards
shoveled into a cart is considered a fair day’s work for a laborer, but a big
steam shovel can easily gobble up as much material in two bites. However,
when we contemplate that this mammoth machine is a human creation and an
absolute slave to human command, we are rather inclined to be puffed up
with the greatness of man.
Steam shovels are ideal machines for excavating railroad cuts and were
primarily developed for just such work. The general operation of the machine
is very similar to that of hand shoveling. The shovel proper consists of a big
scoop or dipper and a dipper handle which correspond respectively to the
blade and handle of a hand shovel. Like the shovel, the dipper is supported at
two points. The dipper is suspended by a chain from the end of a boom while
the handle of the dipper is also supported in the boom. By loosening the
hoisting chain the dipper is lowered to the ground, and by moving the handle
forward the toothed cutting edge is made to bite into the ground or sand bank.
The hoisting chain then hauls up the dipper, making it scoop out the bank,
after which it is swung to one side over a car on an adjoining track. The rear
of the bucket is fitted with a door which is opened by a spring latch and the
contents are emptied out. Some of the largest steam shovels for ordinary
grading have dippers with a capacity of 5 cubic yards. They are not confined
to railroad grading, but are applicable to any excavation where a firm footing
is provided for the heavy machine. They are even used for excavating the
cellars of large city buildings. The machine must be supported on road
wheels or on skids. When used for excavating sewer trenches, it is sometimes
mounted on a platform spanning the trench. However, the steam shovel is
rather limited in its reach. The largest ordinary steam shovels have a clear lift
of but sixteen feet and can make a cut only sixty feet wide at the top.
For more extensive excavating as well as for digging ditches and trenches
the drag-line excavator has recently come in to use. In these machines a

scraper takes the place of the dipper. This is suspended from the end of a long
crane and it is dragged along the ground by a cable, scooping up a load of
earth. In some cases the scoop or scraper is merely attached to a cable leading
from the hoisting engine to an anchorage and back to the engine. To adapt
excavating machines for service in soft ground they are mounted on broad
wheels or on track-laying tractor surfaces. One peculiar form of walking
traction used by a drag-line excavator was described in Chapter XIII.

DITCHING AND TRENCHING MACHINES

For digging narrow ditches and trenches, particularly for sewers, water
mains, gas-pipe lines, etc., a number of very interesting machines have been
invented which are of two general types, the endless chain and the wheel
excavators. The first type consists of a traction engine with a ladder at the
rear that drops down into the trench. About this ladder runs an endless chain
which carries a series of scoops or buckets. These are dragged up against the
breast of the work and carry the excavated earth to the top of the ladder
where it is dumped upon a transverse belt conveyor and carried to one side of
the trench. With the larger sizes of chain excavators, trenches may be dug to a
depth of twenty feet and the width of the trench may be from two to six feet
wide.
The wheel type of trenching machine is similar in principle to the chain
excavator. Instead of the chain of buckets, it has a wheel fitted with buckets.
In one prominent type the wheel has no hub or spokes, but consists of a rim
that is supported on and is turned by four friction rollers mounted in a rigid
frame. This frame is mounted on a boom which can be raised or lowered as
desired. Such machines can commonly dig to a depth of a dozen feet or so.
A ditch differs from a trench in the fact that its side walls are sloping
instead of vertical. A trench is usually a temporary excavation for the laying
of pipes or conduits while the ditch is left open and serves for irrigation or
drainage. There are chain ditching machines in which the chain of buckets
runs laterally across the course of the ditch, dipping into the earth to form a
V-shaped channel. In connection with the draining of the Everglades of
Florida, a peculiar wheel type of ditcher was built. The wheel is of gigantic
proportions, consisting of a series of radiating shovels or scoops shaped to
conform to the outline of the ditch. As the wheel revolves it scoops up the

mud which slides down toward the hub of the wheel and is carried to one side
by a traveling conveyor.

FLOATING EXCAVATORS

The main difficulty in drainage work is to provide a good footing for the
machine which must necessarily be very heavy. Broad caterpillar tread
surfaces are about the only means of locomotion. In very soft swampy
regions dredges have to be used. Dredges are merely floating excavators. In
them the problem of support and locomotion disappear and there are no
limitations of size and weight to be considered. Floating excavators are
therefore much more powerful than excavators that run on land. The ordinary
dipper dredge is merely a floating steam shovel with a much longer dipper
handle and much larger dipper. When work on the slides of the Panama Canal
had proceeded far enough to admit of using dredges in place of steam shovels
material progress was made. Two enormous dipper dredges were built, each
provided with a dipper that had a capacity of fifteen cubic yards or about
twenty tons at a single lift. The dipper was big enough to hold thirty men.
The dipper handle was seventy-two feet long and it could reach down to a
depth of fifty feet. A smaller dipper of ten cubic yards capacity was also
provided. The power of these huge dredges was illustrated when one of them,
while using its ten-yard bucket, picked up an enormous bowlder weighing
forty tons. It was much bigger than the dipper that had raised it and it was far
too big to be placed on the mud scow that was receiving the spoil brought up
by the dredge. Had it been rolled off on the scow it would have crashed right
through the bottom of the boat and so the big rock had to be drilled and
broken up on the dipper before it could be dumped into the scow.
For work on a soft bottom, grab buckets are used in place of dippers.
These may be made of two scoops as in the clam-shell bucket or of four
leaves as in the orange-peel bucket. No rigid handle is provided for these
scoops. They are spread open as they are lowered into the water and on
hauling in the hoisting cable, the scoops or leaves come together biting into
the bottom and lifting up a load of mud. Grab buckets are largely used for
picking up coal, ore, gravel, etc.
The equivalent of the chain trench-digging machine is found in the ladder
dredge. A ladder is hung over the stern of the dredge and carries a chain of
buckets which dig into the bottom and bring up the mud or sand.

GOLD MINING WITH A DREDGE

It is a dredge of this type that is put to the peculiar task of gold mining.
The dredge eats its way into gold-bearing sands, the material passing through
a system of separators which extract the gold and then being discharged at the
rear of the dredge. The dredge floats in a pool of water that it carries with it,
for as it excavates ahead it builds up sand banks behind. In this way it may
travel far from the river from which it first started.

DIGGING A TRENCH WITH A CHAIN TYPE MACHINE

MULTIPLE PLOWING ON A WESTERN WHEAT FIELD—TURNING
FIFTY FURROWS AT ONCE

SUCTION DREDGES

Suction dredges are particularly adapted for excavating sandy bottoms.
One type used for dredging channels consists of a large steam vessel with
large bins into which the dredged material is pumped. At each side of the boat
there is a long pipe which may be let down into the water. Each pipe
terminates in a drag or footpiece with grated opening which is designed to be
dragged along the bottom as the vessel slowly steams ahead. Powerful pumps
suck a stream of water up the pipes which carries with it a quantity of sand.
The sand and water flow into the bins, the solid matter settling to the bottom
while the liquid flows out over the top. When the settlings have filled the
tanks, the drags are pulled up and the vessel steams out to sea. Here doors in
the bottom of the bins are opened and the material drops through. The idea of
opening up the bottom of a boat to empty it seems rather startling until we
consider that the bins are sealed off from the rest of the boat and do not
contribute to its buoyancy. The sand that is dumped out of them is much
heavier than the water that takes its place when the bin doors are opened.

CANAL DIGGING UNDER WATER

The Ambrose channel in lower New York Bay was dredged by means of
suction dredges. The channel is forty feet deep at low water and the bottom
had to be excavated from ten to twenty-five feet to attain this depth. About
seventy million cubic yards of material had to be excavated or nearly a third
as much as was excavated in the Panama Canal. The Ambrose channel is
seven miles long while the Panama Canal is forty-five miles in length. Two of
the larger dredges each had a capacity of forty-five hundred cubic yards in
their bins or enough to load a train about a mile long, composed of 175 cars.
It took less than three hours to fill the bins. The openings in the gratings of
the drags measured about eight by nine inches and any stones or solid matter
small enough to pass through them was easily sucked up into the bins. When
a pile of stones of larger diameter was encountered a deep hole was dredged
around it and then by means of a water jet the stones were forced into the
hole.
The material sucked up by a dredge is sometimes dumped into a scow
alongside. This makes the structure of the dredge less expensive, but where

work has to be conducted in bodies of water exposed to storms it is more
expedient to let the dredge collect the material within its own hull.

LAND BUILDING WITH DREDGES

The sand drawn up by a suction dredge is valuable material for land
building. In fact, a suction dredge is often used for the double purpose of
excavating and filling in low land. Sometimes its only purpose is to fill in
tide flats to above tide level. The material is discharged through a pipe line
which may be over a mile in length. This pipe line is supported on a string of
wooden or steel pontoons. The pipe sections are connected by means of
heavy rubber sleeves so as to make the line flexible. This permits the dredge
to move about and also allows of moving the discharge end about to
distribute the sand properly.
Unfortunately all dredging does not consist of sand and mud. Sometimes
snags and matted roots are encountered which give trouble. For handling
such material rotary cutters are used. The bow of the dredge is fitted with a
hinged ladder about sixty to seventy feet long in which the cutter is mounted.
The ladder also carries the suction pipe close to the cutter. The ladder is
lowered to the bottom and the revolving cutter chops up the roots into pieces
which are drawn up into the suction pipe. The size of the pieces that are
sometimes sucked up is remarkable. The greater part of the area of the New
Orleans Inner Harbor Navigation Canal was filled with stumps and matted
cypress roots. The cutters tore up and cut these roots and stumps and the
pieces were transported through a pipe line about 600 feet long. Stumps that
were too large to be handled in this way were undercut and sunk below grade.
Cutters are used also for loosening packed hard bottoms and some of
them will dig into hard pan and even soft rock. A pressure of 100 to 150
pounds per square inch is maintained in a discharge pipe twenty to twenty-
four inches in diameter, which is enough to carry along heavy bowlders dug
up by the cutter.

THE DEEPEST MINE SHAFT

So far we have dealt only with surface conditions, but man has not been
content to stay on the surface of this planet. True, we have scarcely begun to
explore the crust of the earth. The deepest mine in the world is the Morro

Velho in the province of Minas Geraes, Brazil. Here the earth has been
penetrated to a depth of 6,426 feet in quest of gold. This is a depth of less
than a mile and a quarter and it shrinks into insignificance when we reflect
that we must go more than 3,000 times that distance to reach the center of the
earth. However, we have made material progress in shaft-sinking in recent
years, and it is quite likely that the lure of scientific research may prove even
more powerful than that of gold and that some day we shall be induced to dig
many miles into the crust of the earth just to learn something more about this
globe that whirls us through space.
We have not yet reached the point at which hand labor may be dispensed
with in tunnel work, but there are machines which will do what formerly
could only be accomplished with the manually wielded pick and shovel. We
have already (in Chapter VII) described the pneumatic tunnel shield and
explained how it is sometimes driven forward through soft silt by means of
hydraulic jacks without any excavation of material. This method of tunneling
which is analogous to driving a punch through soft metal, has a very limited
field of application. It is impossible to force the shield in this manner through
sand or through any but very soft silt.

TUNNELING BY MACHINE

The city of Cleveland takes its drinking water from Lake Erie. In order to
obtain water that is not contaminated by the refuse of the city, tunnels are
carried out under the bottom of the lake about two miles from the shore
where they terminate in water intakes far enough below the surface to avoid
floating impurities and far enough above the bottom to avoid impurities that
have settled to the lake bed. The material through which the tunnels pass is a
stiff clay, that cuts like cheese. So uniform is this material that a special
machine was built to bore the tunnel through it. This machine is somewhat
similar to a boring mill. It has an arm that revolves against the face of the
tunnel heading and carries a cutter that travels along the arm so that it cuts a
continuous spiral ribbon of clay. The clay ribbon passes back through the
machine and is loaded into a train of dump cars.
For boring tunnels in hard rock many different machines have been
invented, but not one of them as yet has proved an unqualified success. One
very interesting machine, which was tried on the New York subway
excavation at 42d Street and Lexington Avenue, consisted of a series of

chipping hammers which, by means of pneumatic mechanism, were made to
hammer and pulverize the face of the rock with repeated blows. The hammers
were arranged in a circle and were revolved as they hammered so that the
whole surface of the heading was attacked and a circular tunnel was cut
through the rock. A serious disadvantage under which the machine labored
was the fact that the rock had to be crushed to a powder or into small chips
before it could be removed.
In ordinary rock excavation holes are bored into the heading and the rock
is then blown out by means of dynamite or some other explosive. Large
fragments of rock are then broken up into pieces small enough to be handled
readily, but no energy is wasted in reducing the material to a powder. The
percussion drills with which the rock is bored have already been briefly
described. When boring holes for a blast in soft material, such as bituminous
coal, a drill is used which resembles in many respects an ordinary twisted
auger bit except that it is many feet in length. It is driven by hand into the
coal by the use of a common bit brace. Percussion drills or punches are also
used. These are driven either by pneumatic or electric power.

COAL-CUTTING MACHINERY

When excavating coal the heading is first undercut, that is, a deep slot is
cut in the wall of coal along the floor line. Then blast holes are bored into the
coal above this cut so that when the charges are fired the coal will be broken
downward. To undercut the coal special machines are used, driven by
compressed air or electricity. These have endless chains fitted with chisel or
pick points that bite into and cut the coal. After the material has been
shattered and reduced to fragments of convenient size special machinery may
be employed to shovel it away from the heading and into dump cars. One
electrically driven shoveling machine which was tried out on some of the
Catskill aqueduct excavation had a broad open shovel which could be driven
into the pile of rock fragments under the control of an operator and would
scoop up the material, delivering it upon a traveling belt conveyor which
carried it on to the train cars. Many types of mechanical shoveling and
loading machines have been built for use in mines. They are driven either by
pneumatic or electric power.

EXPLORING SUBSURFACE CONDITIONS

In all engineering work it is highly important to explore subsurface
conditions before starting any construction or even drawing up plans. The
ordinary pneumatic percussion drill will not serve for deep holes. Instead a
rotary boring motion is requisite. The tool is mounted with black diamond
cutters which cut through the hardest rock. Water is introduced into the hole
to lubricate the tool and also to wash out the abraded material. By trapping
this material the character of the rock penetrated may be determined. The
material, however, is pulverized and does not furnish, as a general rule, a fair
sample of the rock. When it is highly important to determine the exact nature
of the rock or other material a core drill is used. In other words the drill is a
hollow tube set with cutting crystals about its periphery. As the tool is
revolved it cuts an annular slot in the rock leaving a central core standing.
This core is broken off and drawn to the surface and furnishes a true sample
of the material encountered by the drill.
There is an interesting type of core drill in which steel shot is used in
place of diamonds. The cutting end of the drill is a collar with a notched
edge. Steel balls are fed into the drill and under the cutting head. The balls
are caught in the notches and rolled around against the rock surface. There is
also a partial dragging action. The friction is sufficient to wear away the rock.
As the balls wear away they are replaced with new ones. Very evidently such
drilling costs less for upkeep than diamond drilling, but it is not as rapid as
the latter.

LOCATING ROCK UNDER HUDSON RIVER

A notable illustration of exploration drilling was furnished by the surveys
for the Hudson crossing of the Catskill Aqueduct. To bring water from the
Catskill Mountains to New York City it was necessary to cross the Hudson
River. In order to furnish a permanent conduit it was decided to carry the
water in an inverted siphon bored through solid rock. It was necessary to
obtain a profile of the rock at the point where a crossing seemed most
feasible. Borings were therefore made from a barge anchored in the river, but
it was impossible with such an unsteady working base to carry on the boring
to any considerable depth. Tides, the wash of passing steamers, floating ice,
all combined to obstruct the work. Drills were constantly broken. Finally it
was decided to do the boring from opposite banks of the river at such an
angle that bore holes would meet or pass each other under the middle of the
river. The exploration boring from the barges indicated that solid rock lay at a

considerable depth below the river bed and that the bore holes would have to
be set at a sharp angle to keep from breaking through rock. The river at that
point is about 3,000 feet wide and a boring from the surface at the middle of
the river had been driven to a depth of 768 feet without striking solid rock.
Two shafts were sunk to a depth of about 250 feet and from these diamond
drill borings were started at such an angle that they would cross at a depth of
1,500 feet. Excellent rock was encountered throughout the boring. Then a
second set of borings was made which crossed at a depth of 950 feet without
encountering any appreciable amount of water. It was accordingly decided to
carry the aqueduct in vertical shafts, one at each side of the river, at a depth
of 1,100 feet below water level, and then connect these shafts with a
horizontal tunnel. It was important to have a good solid rock cover over the
tunnel because the aqueduct reaches the river with a head of 400 feet which
added to the 1,100 feet of depth of the inverted siphon gave a total head of
1,500 feet or a hydraulic pressure of about forty-two tons per square inch.
Although the diamond drill borings just mentioned were remarkable
because of their inclination and because of the cramped quarters from which
they were driven, they do not begin to compare in depth with some of the
borings made in search of water and of oil. The deepest boring in the world to
date is near Fairmount, West Virginia, where a hole six inches in diameter
was driven to a depth of 7,579 feet or nearly a mile and a half. At that point
an earth slide stopped further borings.

BORING FOR OIL

The time-honored method of boring for oil known as the percussive
system is to hammer through the earth and rock with a heavy steel drill. The
drill really consists of a long string of parts measuring altogether as much as
sixty feet in length. (See Figure 64.) The drill proper or bit has a cutting edge
adapted for the character of the material it is to penetrate. The bit is attached
to a steel bar known as the “auger stem” which may be from twelve to forty-
five feet in length. Then come the “jars” or a link member which allows a
play of about sixteen inches. The purpose of this is to assist in freeing the bit
from the material it is penetrating by jarring it upward on the upstroke of the
drill. Above the jars there is another bar known as the sinker, and this is
provided with a rope socket to which is attached the cable that carries the
string of drill parts. The cable passes over a pulley to a walking beam which
gives the necessary up-and-down motion.

FIG. 64.—A STRING OF WELL-DRILLING TOOLS

The loose material in the bore is removed by a sand pump. To protect the
bore from caving a casing of steel pipe must be lowered into the well. The
boring may proceed at the rate of ten to sixty feet per day, depending upon
the material penetrated and the depth of the well. All sorts of difficulties are
liable to interrupt the work. The cable may break, the string of tools may
become unscrewed, or the casing may drop into the hole, and then follows
the tedious process of fishing for the lost parts and hauling them up out of the
well.
As the drilling proceeds, the bore becomes progressively smaller and
casings of smaller diameter must be used. The well is completed by lowering
a pipe within the casing through which the oil flows to the surface and is
carried to the storage tanks and thence by pipe lines to the refineries.
While the percussive system of drilling is very generally used throughout
the American oil fields, rotary methods of drilling are largely employed in
California.

CHAPTER XVII

FROM FIBER TO FABRIC

I
T IS NOT very long since the spinning wheel and the clacking loom
were an indispensable furnishing of every farmhouse and of many city
dwellings as well. With infinite patience the fleece of sheep, the lint of
flax, the filaments of silk and the fibers of cotton were spun into yarn
and then woven into cloth, and it was the nimble fingers of the housewife
that carried the process through from the matted raw product to the finished
garment.
It is comparatively easy to comprehend the development of machines
for dealing with such gross material as earth, rock, iron, and wood, but
when we come to consider the infinitely delicate and almost imponderable
fibers that go to make up our textiles, the marvel is that any but highly
skilled human hands, guided by keen eyesight, could combine the tangled
and obstreperous filaments into fine yarn and weave this yarn into
complicated patterns of cloth. But the spinning wheel and hand loom could
not stand long in the path of power-driven machinery, and now huge, blind
machines, with stiff, unbending fingers of metal, comb out the matted
masses of raw material, remove the dirt and twigs, straighten out the snarls
far quicker and better than could be done by hand, and transform the fibers
into beautiful fabrics such as in former days would have been the envy of
kings.
We cannot attempt to describe all the machinery involved in the
spinning and weaving of yarn, but it is highly important that every well-
informed person have a general knowledge of textile machinery. Because
cotton cloth is more widely used than either linen or wool, we shall confine

ourselves to the cotton branch of the textile industry, particularly as the
difference between the treatment of cotton and other textile materials lies
chiefly in the preparation of the thread or yarn.
The predominance of cotton among textiles may be traced back to the
invention of a young New Englander fresh from college, who went to
Georgia as a private tutor, only to find when he got there that some one else
had been engaged in his stead, leaving him stranded and practically
penniless in a strange land. We had occasion to refer to this man in Chapter
III. Eli Whitney was a born mechanic, and before entering college had not
only shown great skill but had actually built up a thriving business in the
manufacture of nails, hatpins and knife blades.

INVENTION OF THE COTTON GIN

The agricultural condition of Georgia and its neighboring States at the
time that Whitney arrived there was very poor. There was no market for
their products. A splendid cotton, with fibers from 1⅜ to 2½ inches long,
was growing on the islands along the coast, but this cotton could not be
raised inland. The upland product, known as “green seed” cotton, had a
fiber only half as long as the “Sea Island” cotton, but the principal
drawback to its use was the difficulty of separating the fiber from the seed.
It was a day’s work for one woman to separate a single pound of the “green
seed” cotton fiber.
His attention having been brought to this matter, Whitney undertook to
design a machine which would remove the fiber from the seed in a small
fraction of the time required by hand labor. He was visiting at the time at
the plantation of Mrs. Greene, widow of General Nathaniel Greene, of
Revolutionary fame, and he set himself to the task with such limited
materials and tools as he could find on the estate. In a couple of weeks he
had built a model which contained all the essentials of the modern cotton
gin, with which a single man could separate more cotton in a day than could
be produced by hand in a whole season. This was in the winter of 1792. The
effect of the invention was felt immediately. Cotton production had been
falling off steadily. In 1791, 189,316 pounds of cotton had been exported.
The next year there was a falling off to 138,328 pounds, but following the
introduction of the cotton gin exports rose to 487,000 pounds in 1793,
1,681,000 in 1794, and 6,276,000 in 1795. Fifty years later the world

production amounted to 1,169,600,000, nearly seven-eighths of which was
contributed by the United States, and of this only a small amount was Sea
Island cotton.
A cotton gin (Fig. 65) consists of a gang of circular saws (A), with
forwardly pointed teeth which pass between the ribs of an inclined grating
(B) that forms the floor of a chamber (C) known as a roll box. In this box is
mounted a toothed roller (D). The cotton is fed into the box and the fibers
are seized by the teeth of the saws and dragged through the grating while
the seeds, being too large to pass through, are left behind and, rolling down
the grating, drop into a hopper. The action of the saws is such as to impart a
rolling motion to the mass of cotton, and hence to the roller in the roll box.
This tends to drag the cotton into the roll box and bring fresh supplies to the
saws. The fleece carried by the saw teeth is beaten off by a wheel (E) fitted
with wire brushes. These brushes, traveling in the same direction as the saw
teeth, but at a higher velocity, readily disengage the fibers from the teeth
and create an air blast that blows the cotton fleece out of the gin.

FIG. 65—SECTIONAL VIEW OF A COTTON GIN

PREPARING COTTON FOR THE SPINNING MULE

Cotton as it comes from the bale is a compact, matted mass, mixed with
bits of seed, leaves, sand, and other impurities, and it must pass through a
number of machines before it comes out as a pure, light, fleecy product,
with the fibers combed parallel. Even for a medium yarn a dozen machines
are required to prepare the cotton for the spinning mule.
A system of “counts” is used to indicate the size of yarn and it is based
on the number of hanks it takes to make a pound. A hank is always 840
yards and 50’s would mean that the yarn is of such fineness that it would
take 50 × 840 yards (=4,200 yards) of it to weigh a pound. Yarn below 30’s
is graded as coarse; between 30’s and 60’s as medium and above 60’s as
fine. To prepare cotton as it comes from the bale for a fine yarn of, say,
100’s, it must go through no less than sixteen machines before it reaches the
mule.
We have not the space to describe all of these machines, but in general it
will suffice to say that the cotton is graded by passing it through a series of
pickers. These machines throw out the fibers and beat them so as to knock
out the impurities and, at the same time, a blast of air blows out the dust.
The cotton is treated by a number of such machines in succession and is
finally delivered in a broad sheet known as a “lap,” after which it passes
through the carding machine which combs out the tangled bunches and
removes further impurities from the lap. The lap is then gathered into a
compact rope known as a “sliver.” The sliver goes through the drawing rolls
which serve to parallelize the fibers and make the sliver of even thickness,
and at the same time to give a moderate amount of twist so that it will hold
together, and it issues from the machine as “roving.” In the case of fine yarn
the sliver issuing from the carding machine goes through a combing
machine so as to remove the finer fibers. The bobbins of the roving are then
placed in the spinning machine, which may be either the spinning mule or
the ring spinning machine. The principal difference between the two is that
the spinning mule is intermittent in its operation, while the ring spinner not
only spins the roving into yarn but at the same time winds it up on a bobbin.

FIG. 66.—ARKWRIGHT’S DRAWING ROLLS

ARKWRIGHT’S DRAWING ROLLS

The first advance over the old-fashioned spinning wheel, which dates
back to the fifteenth century, was in 1770, when the first spinning jenny was
invented by Hargreaves. This consisted practically of a multiple spinning
wheel by which one man could spin a large numbers of bobbins of yarn at
the same time. It was at about the same time that Arkwright invented the
drawing rolls which have played a most important part in the preparation of
yarn, and this invention is worthy of our attention because it contains an
interesting mechanical principle. As shown in Figure 66, a number of pairs
of rolls are provided through which the roving passes, but successive pairs
operate at higher velocities. Thus, the second pair of rollers through which
the roving passes run at a little higher speed than the first pair, the third a
little higher than the second pair, and so on. As a result, the roving is drawn
out by the operation and issues from the last pair of rollers at a higher speed
than it entered the first pair of rollers. The only way in which it can

accommodate itself to this accelerated motion is to be attenuated or drawn
out. Weights are used, as shown in the drawing, to press the upper rollers
against the lower ones.

THE SPINNING MULE

Shortly after Arkwright’s invention came the mule spinner, invented by
Crompton between 1774 and 1779. Machines operated on the same general
principle as this are in general use to-day. In the old-fashioned method of
spinning by hand the worker took a small quantity of cotton, pulled it out
into a long sliver, attached one end to a bobbin and gave the bobbin a twirl
between his hands in order to spin the fiber into yarn; then the yarn was
wound up on the bobbin and the process was repeated. The spinning mule
does practically the same thing, but infinitely faster and on a much larger
scale. As shown in Figure 67, the bobbins of roving (A) are mounted on a
stand and passed through a set of drawing rolls (B) which are regulated to
pull the rovings out to the desired thickness of yarn. The roving then passes
to the nose of a “cop,” or spindle (C), which is revolved at very high speed.
The cop is carried by a carriage (D) which moves away from the bobbins of
roving to the position indicated by dotted lines, while the cop is revolving.
The cop has a travel of about five feet during the time the yarn is drawn out
and spun. Then the carriage moves back toward the stand upon which the
bobbins of roving are mounted and the spun yarn is wound up on the cop.
The reason the yarn does not wind up on the cop while it is spinning is
because it runs to the nose of the cop and, at each turn of the cop, the coil
twists on the nose and slips off. On the return of the carriage, however, a set
of wires (E), called “fallers,” press the yarn down so that the revolving cop
will wind up the slack.

FIG. 67.—DETAILS OF A SPINNING MULE

The continuously operating ring-spinning machine is provided with a
ring frame (Figure 68) around the cop or spindle. This frame, together with
the spindle, revolves at high speed, but as the ring revolves a little more
slowly than the spindle it winds the yarn comparatively slowly upon the
spindle or bobbin.

WOVEN, BRAIDED, KNITTED, AND NET GOODS

Having now produced our yarn, we may pause to consider the different
types of fabric into which it may be formed, and to draw a distinction
between, woven, braided, knitted, and net goods. In weaving we have two
sets of threads, one set running transversely to the other; in braided
materials the threads all run longitudinally and are arranged to cross each
other diagonally, so that they are interwoven; in knitting and netting there is
a single thread. In the case of netting this thread is knotted where it loops
back upon itself, whereas in knitting it is merely looped without knotting.

THE LOOM

The loom can trace its genealogy away back to early Babylonian times,
and the modern power-driven machine does not differ in its broad principles
of operation from its ancient progenitor—the hand loom.

FIG. 68.—RING-SPINNING FRAME

FIG. 69.—THE HEDDLES OF A LOOM

Every industry has a vocabulary of its own to furnish names for its
machine parts and products peculiar unto itself, and in this respect the
textile industry is by no means an exception. The threads that run
lengthwise in a piece of woven cloth are known as the “weft,” “woof” or
“filling.” In the loom the warp threads are threaded through loops on what
are known as “heddles”; in fact, there are two “heddles,” A and B, Figure
69. Alternate warp threads (C) pass through the loops of one heddle, and the
other threads through the loops on the other heddle. When one heddle is

raised and the other lowered, the threads form a wedge-shaped space (D)
which is known as a “shed.” The filling thread is sent through the shed and
is then pressed closely into the wedge-shaped space against the cloth
already woven by means of a “reed” (E) which is a comblike member with
teeth or flat pieces of metal that pass between the warp threads. This done,
the position of the heddles is reversed, so that A is now lowered and B
raised, thus binding the warp thread in place and forming another shed for
the next warp thread; and thus the process continues.
The filling thread is placed in a shuttle (F) which carries a bobbin on
which the thread is wound. As the shuttle is thrown back and forth through
the shed, the thread is unwound and trails behind it. Formerly the shuttle
was thrown back and forth by hand, but years ago, long before the invention
of the steam engine, the flying shuttle was invented. In other words, a
mechanism was provided for striking the shuttle a blow and throwing it
across the warp from side to side. By this means the speed of operations
was greatly increased.
About the middle of the eighteenth century the drop box was invented.
This consists of a receptacle for shuttles carrying different colors of thread
which may be selected in a definite order and thrown back and forth so as to
vary the pattern of the cloth.
In present looms a special machine is provided for taking the threads
from the bobbins or cops and laying them in an even sheet to form the warp
of the loom. These are wound on a beam and the machine is known as a
beam warper. As the threads are apt to be somewhat fuzzy it is necessary to
size them, and a machine known as a slasher is employed for this purpose.
This machine coats each thread of warp yarn with a sizing compound or an
adhesive and dries the sheet of warp preparatory to its use in the loom.
In common weaving the weft or filling threads run alternately under and
over the warp threads with perfect regularity. A pattern can be formed by
passing the weft threads under and over alternate groups of warp threads,
and this is effected in the ordinary loom by threading the weft in groups
through the heddles, i. e., instead of having every second thread pass
through one heddle and the intervening threads through the other heddle;
the threads are arranged in alternate groups of two or more. This gives a
regular pattern, but it may be varied to form ornamental designs if the

groups are varied. Such designs used to be worked out by hand very slowly
and laboriously, with the result that figured weaving was very expensive.

THE JACQUARD LOOM

At the French Exposition of 1801 a loom was exhibited that made a
sensation. With seemingly human intelligence it selected individual warp
threads or groups of threads and raised them or lowered them so as to work
out elaborate ornamental designs. The inventor, Joseph Marie Jacquard, of
Lyons, received a medal for his marvelous invention and was decorated
with the Cross of the Legion of Honor.
The “brains” of the Jacquard loom is a set of pasteboard cards that are
perforated in accordance with a prearranged design. The warp threads,
instead of being passed through the loops of two heddles, are passed
through what might be termed individual heddles, one for each thread, or
for a small group of threads. These consist of cords in each of which is an
eyelet through which the warp thread passes. The cord is weighted at its
lower end and its upper end is fastened to a hook in a box at the top of the
machine. The hooks engage transverse bars known as “griffes” or “knives,”
and when the griffes are raised, the hooks engaging them are also raised. In
this way the warp threads that pass through the eyelets that are connected to
the hooks are raised. But running horizontally across the hooks there are
“needles” or rods with eyelets or bends in them through which the hooks
pass. These needles may be moved lengthwise to make the hoops engage or
disengage the knives. The mechanism is illustrated in Figure 70, where the
knives are shown in section at A, the hooks at B and the needles at C. For
the sake of simplicity only eight hooks and needles are shown; in actual
practice there are hundreds in a single machine. At the right-hand end of
each needle there is a spring which pushes the needle toward the left,
thereby bringing the hook through which it passes into position to be lifted
by its griffe. At the left-hand side of the machine there is a card (D) which
presses back the needles and thereby bends the hooks out of position to
engage the griffes. However, there are perforations in the card through
which certain of the needles can pass, letting the hooks they control engage
the needles. The cards thus select the particular weft threads that are to be
raised. In our illustration most of the needles have entered holes in the card,
but the second, fourth and sixth from the top have been pushed back by the

blank wall of the card and their hooks have been bent back clear of the
griffes. Only four cards are shown in the drawing arranged in a four-sided
box or “cylinder,” and the cards are successively presented to the needles.
For more elaborate designs a large number of cards are used, arranged in a
slatted belt, and these come successively into position. As many as thirty
thousand cards have been employed to carry out a single pattern.

FIG. 70.—DETAIL OF A JACQUARD LOOM

INVENTION OF THE KNITTING MACHINE

We are wont to call Necessity the Mother of Invention; in many cases
Laziness has given rise to valuable inventions, but according to legend,

Cupid played the leading rôle in the development of the knitting machine. It
is said that in 1589 William Lee of England fell in love, but the girl who
was the object of his devotion was always so busy with her knitting that she
could not give him the attention he sought or thought he deserved.
However, Lee was not to be thwarted in this fashion, so he built a machine
to do the knitting in order that the girl could devote herself more completely
to him.
There is another less pleasant version of the story to the effect that Lee
became so attached to his knitting machine that he neglected the girl.
However, in either case, love was somehow mixed up in the invention of
the knitting machine.
We are not going to attempt to delve into the complicated mechanism of
a modern knitting machine, but will merely call attention to the fact that
modern machines perform automatically practically all the movements of
the human hand in hand knitting.
The tendency of modern machinery has been to relieve the housewife of
the tedious work she formerly performed and to take such work away from
the home to the factory. There is one important machine, however, which
has been introduced into the home, apparently to stay; for in the majority of
houses it is still considered indispensable. It is a fact that the introduction of
labor-saving machinery into the household has, until recently, met with
stern opposition on the part of the housewife. It is all the more remarkable,
therefore, that in the middle of the nineteenth century the sewing machine
began successfully to invade the home.

HOWE’S INVENTION OF THE SEWING MACHINE

It was in 1844 that Elias Howe hit upon the brilliant idea of putting an
eye at the point of a needle. This enabled him to produce a successful
sewing machine, because it was unnecessary for him to pass the needle
completely through the cloth in order to pull the thread through it. When the
needle point penetrated the cloth a shuttle passed through the loop of thread
that was carried through with the point. This shuttle carried a second thread
which interlocked with the thread of the needle forming what is known as a
“lock stitch.” In Howe’s machine the cloth was held vertically and the
needle which was curved was carried by a lever. The needle was driven

through the cloth with a swinging motion, somewhat like that of a pick-ax.
The shuttle was driven back and forth by a pair of strikers after the manner
of the flying shuttle of a loom. George Fisher, a friend of Howe, furnished
$500 with which the first successful machine was built in 1845, and with
this machine Howe sewed two suits of clothes, one for Mr. Fisher and the
other for himself. A public exhibition was held at which the machine, crude
as it was, beat five of the best hand-sewers that could be found. In 1863
Howe was reaping a fortune in royalties from his machine which were
estimated at $4,000 per day.
The next notable improvement in sewing machinery was that of the
rotary bobbin, invented by A. B. Wilson, which was patented in 1852. This
did away with the flying shuttle and simplified the machine considerably. It
made the sewing machine comparatively quiet, thus adapting it for domestic
use. In Wilson’s machine, a rotating hook passed through the loop of thread
and carried it around the bobbin on which the lower thread was wound.
Wilson also invented the four-motion feed for feeding the cloth under the
needle. Sewing machines up to that time had been operated by hand, but
Isaac Merritt Singer introduced a foot-power machine and by progressive
business methods built up a thriving industry and did much to establish the
sewing machine, not only at home, but abroad as well.

THE SINGLE-THREAD SEWING MACHINE

The single-thread machine was invented by a Virginia farmer who had
never seen a sewing machine. James E. A. Gibbs had seen a picture of a
sewing machine and, unaware of the fact that there was a shuttle carrying a
second thread on the rear, or under side of the cloth, fell to puzzling over
the problem of what happened to the thread carried by the needle through
the cloth. Somehow, it seemed to him, the loop of thread must be held until
the next stitch carried another loop of thread through it, thus forming a
chain stitch. This led him to invent an ingenious revolving hook. With
infinite patience he whittled out a model of his invention, and it is this hook
that is the outstanding feature of the Wilcox and Gibbs machine.

MACHINE-MADE EMBROIDERIES

A notable modern development of the sewing machine is its adaptation
to the making of embroideries and even laces. In the common domestic
sewing machine the cloth is fed step by step under the needle, and the
length of the step regulates the size or length of the stitches. The feed may
be set for short or long stitches. It is evident that if a greater range of length
of stitch were provided, and if, while the machine was operating, the stitch
could be varied at will, not only in length but in the direction as well, it
would be possible to work out elaborate patterns of embroidery. This is
what is done on the power-driven embroidery machines. Like the original
Howe machine, the cloth is held vertically and a series of needles are used
which pass horizontally through the cloth. As the needle retreats, the thread
it carries forms a loop on the rear or “wrong” side of the cloth, and through
this a shuttle is driven which carries a thread wound upon a bobbin.
Between stitches the cloth is moved this way and that, in accordance with a
prearranged pattern, and thus the design is embroidered. A single machine
may have several hundred needles and, as they all work in unison, each
needle repeats the design. The arrangement is such that one needle starts
where the next one leaves off, so that the embroidery is continuous. The
shuttles which operate on the wrong side of the cloth are small, boat-shaped
parts which the Swiss have named “schiffli” or “little ships,” and this name
has come to be applied to the whole machine.
The guiding of the cloth to produce the required design is accomplished
either by hand or automatically. In the hand-guided schiffli machine a
skilled “stitcher” seated at one side of the machine operates a pantagraph,
tracing an enlarged design mounted on a board before him. As he moves the
lever vertically and horizontally the frame carrying the cloth is
correspondingly moved before the needles. An expert stitcher can put a
great deal of individuality into the work, which is impossible in the strictly
automatic machine; accordingly the pantagraph is used for the finer grades
of embroideries. In the automatic machines a perforated roll like that of a
piano player is used. The perforations control the movements of the frame
that carries the fabric.

FINE NEEDLEWORK BY MACHINE

These machines are of Swiss and German design, but American
inventors have recently developed a machine for producing fine needlework

which imitates very closely the work of the hand. In this machine the needle
passes completely through the fabric as in ordinary hand sewing, but it does
not have to be turned around for the return stitch because it is pointed at
each end and has the eye in the middle. The needles are held by spring clips
in a swinging frame. When the frame swings toward the cloth the needles
are pushed through the fabric and their points are caught by spring clips in a
frame on the opposite side. The latter frame draws the needles completely
through and a set of hooks catch the thread and pull the stitch taut. The
advantage of this type of machine is that it produces the same design on
each side of the cloth; in other words, there is no “wrong” side to the
embroidery. The design is controlled by a “stitcher” operating a
pantagraphic system of levers and by skillful manipulation he can
completely overcome the flat machinelike appearance of the automatic
schiffli machine.
Laces are very ingeniously produced on schiffli machines by using the
“burnt-out” system invented forty years ago by a German, named Beckel.
This consists in the use of thread of a different material from that of the
fabric, and after the embroidery is completed the fabric is removed either
chemically or by the application of heat, leaving only the stitching, which
forms a delicate lace. For instance, cotton thread may be embroidered on a
groundwork of wool, or silk thread is used on a fabric of cotton. Laces
made in this way are known as Plauen laces, taking their name from the city
where Beckel invented the process, and they form a large part of the
machine-made laces that are now so widely used.

SAWING LOGS INTO 16-INCH LENGTHS PRIOR TO GRINDING
THEM INTO PULP

Copyright Kadel & Herbert
THE HEATER IN A PULP MILL WHERE THE WOOD PULP IS
MIXED WITH CLAY

A MODERN FOURDRINIER PAPER-MAKING MACHINE

CHAPTER XVIII

THE MAKING OF PAPER

T
HE MAKING of paper is closely related to that of textiles. In each case
the same basic materials are used. A mass of interlacing fibers is
formed into a continuous sheet, but the method of interlacing the
fibers and holding them together is entirely different. Paper resembles
felt more closely than any other form of fabric. The fibers are not woven but
are matted together and compressed. In the case of felt the fibers of wool or
hair are held together mainly by the microscopic barbs that they possess
while paper fibers are held together by means of sizing.
Although paper gets its name from papyrus the latter was not paper, for it
was a felt of pith rather than fiber. The ancients produced a very fair writing
material from the rushlike plants that grew in the swamps along the Nile. The
stem of the papyrus was stripped of its bark and the pith was cut into thin
ribbons which were laid side by side to form a sheet. Over these and at right
angles to them was laid another layer of pith ribbons. The material was then
soaked in water, pressed into a continuous sheet and dried. These sheets were
then pasted together and rolled up into scrolls. Unquestionably they played a
most important part in the civilization of ancient Egypt, providing, as they
did, a ready means of recording knowledge and disseminating it among the
people.

CHINESE INVENTION OF PAPER

Like so many inventions that are of vital importance to modern
civilization, paper is a Chinese invention. The Chinese made paper from the
fibers of trees, a material to which we have reverted in recent years. The

invention dates from about 150 A. D., when some one devised a process of
reducing the bark of the mulberry tree to a pulp, beating it and boiling it in
lye and then matting the fibers on a screen and pressing them into a finished
sheet. The process was introduced into Europe by the crusaders in the 12th
Century. In 1150 a paper-making plant was established in Italy and soon the
new writing material was being made in increasing quantities and became a
common article throughout Europe. It was not until the end of the 18th
Century that machinery for making paper came into use.
In the old hand process which is still used to a very limited extent for
special papers, the pulp, after being reduced to a thin milky fluid, was dipped
out of a vat with a rectangular sieve which had a wire screen bottom of fine
mesh. The water drained off, leaving the fibers upon the screen. As the pulp
was draining the sieve was shaken about to distribute the fibers evenly and
interlace them as much as possible. The depth of the sieve determined the
amount of pulp that was dipped out and hence the thickness of the paper. The
soft, matted mass of fibers was turned out upon a felt mat and left to dry.
Soon other fibers came to be used and the finest grades of paper were made
from linen and cotton rags. The rags were carefully sorted out and washed
after which they were stored in a damp place to rot for a number of weeks.
Then they were cut and shredded and boiled until they were converted into a
pulp. The complete process of making fine paper by hand took from two to
three months. Paper was made in small sheets limited by the size of sieve that
could readily be operated by hand.
The first man to make a continuous web of paper was Nicholas Louis
Robert, a Frenchman who received a reward of 8,000 francs from his
government for his invention. Robert’s patent rights were acquired by the
Fourdrinier Brothers (Henry and Sealy), of England. They developed and
perfected the machine and to them is ascribed the honor of founding the
modern paper industry.

USES OF PAPER

Paper is more commonly and extensively used to-day than any other
product of manufacture and is employed for an astonishing variety of
purposes, ranging from milk bottles to suits of clothing. One very novel use
we might mention, in passing, is to be found on the sugar plantations of
Hawaii. After the cane is planted the fields are covered with a thick paper

made, by the way, from sugar-cane fiber. This covering prevents the weeds
from growing, but the sharp spikes of the sugar sprouts pierce the paper and
grow through it. By the time the paper has disintegrated and the weeds have a
chance to grow, the cane has such a start on them that they are kept shaded
and cannot compete with or choke out the cane.

TURNING FORESTS INTO PULP

Before we proceed to describe the modern Fourdrinier machine, we must
look into present day methods of preparing pulp. The finest papers are still
made from linen and cotton rags. Esparto grass is largely used in Europe.
This comes from Spain and North Africa. But by far the greater part of the
paper produced to-day is made from the fiber of trees. Particularly is this true
of our own country, which consumes half of the world’s output of paper.
It used to be that only the poorest grades of paper were made from wood
pulp; now however not only newspapers but nearly all books and magazines
are printed on a forest product. Formerly only spruce wood was considered
suitable for paper manufacture, but the rapid depletion of this raw material
led to the employment of many other species of trees and our Government
scientists are constantly searching for and experimenting with new woods for
this purpose.
Because of the insatiable appetites of our large newspaper printing
presses and because a newspaper is not intended to be an imperishable
document but a fleeting record of passing events, quality is of little
importance in the preparation of pulp for newsprint and everything must be
sacrificed for speed. The pulp is made of “ground” wood as distinguished
from the chemically prepared wood pulp known as “sulphite.” The wood is
first stripped of its bark and then cut into pieces running from two to four feet
in length, depending upon the size of the magazine of the grinder. The wood
is pressed against a revolving grindstone by hydraulic pressure and at such an
angle that the fibers torn off will be as long as possible. The fibers are borne
off by a stream of water which carries them through a set of screens. These
remove any unground slivers, and eventually the pulp is drained of water and
pressed into laps, or, if it is to be used immediately, it goes directly to the
beating engine. Here it is mixed with a certain amount of “sulphite pulp,”
usually from 20 to 25 per cent. To correct the yellowish color of the pulp, a
small amount of blue and red coloring is added. To give body to the paper

from 5 to 15 per cent of clay is mixed into the pulp and, to bind the fibers
together and give the paper a finish that will be at least partly nonabsorbent, a
quantity of rosin and soda ash is added with enough alum to precipitate the
rosin upon the fibers. The beater thoroughly mixes the mass of material and
converts it into a fluid of the consistency of thin milk, which then passes on
to the Fourdrinier machine.

GETTING DOWN TO THE “BONES” OF THE WOOD

Paper made from ground wood pulp soon discolors and becomes brittle
owing to the presence of the lignin and resin of the tree. The superiority of
sulphite pulp is due to the fact that chemical processes are used to remove
these disturbing ingredients, leaving only the “bones” of the tree, that is, the
pure cellulose fiber. Spruce wood is usually used and after being freed of its
bark and thoroughly cleaned, all knots are cut out and it is sawed into short
lengths which are then split and cut up into little chips from ¼ to ½ inch long.
These chips are boiled under pressure in a solution of sulphur dioxide and
slaked lime. The “digesters” in which the chips are boiled are large steel
cylinders lined with brick set in cement and coated with litharge and glycerin,
so as to prevent the sulphite liquor from coming into contact with the metal.
A steam pressure of seventy to eighty pounds is maintained for eight to ten
hours and then the digesters are discharged into vats. The sulphite liquor in
which the resinous matter is dissolved is drained away and the pulp is
washed.
Soft woods, such as poplar, basswood, etc., are boiled in caustic soda,
producing what is known as “soda pulp.” “Sulphate pulp” is made by boiling
in a solution of sodium sulphate, to which a certain amount of sodium
carbonate and caustic soda are added. This process is used for producing pulp
for so-called “Kraft” paper and brown wrapping paper.
Formerly pulp was always made in the paper mill and hence the mills had
to be located near the source of wood supply, but to-day the making of pulp is
carried on as an independent industry in remote forest regions where water
power is plentiful. The pulp is pressed into laps and compressed into bales
weighing about 400 pounds. These are sent over long distances by rail or
steamship to paper mills located in or near the big cities, so that the paper
may be made near the points of consumption.

Baled paper pulp has to be reconverted into a smooth milklike fluid. A
shredding machine is used for this purpose, which tears the pulp apart and
mixes it with water. Then it goes to the beater where it receives its quota of
sulphite pulp, coloring matter, clay, and sizing, as explained before. After an
hour of treatment in the beater, it passes on to a tank in which it is further
diluted with water and is then put through a Jordan engine. This consists of a
conical cylinder in which is placed a conical roll. Both cylinder and roll are
formed with knives that extend longitudinally, but the revolving knives are
set at a slight angle to the fixed knives, somewhat after the fashion of a lawn
mower. The conical form permits of careful adjustment of the roller in the
cylinder. The pulp mixture enters at the smaller end and discharges at the
larger end. This machine gives the pulp its final beating and reduces it to a
very smooth consistency.

THE FOURDRINIER PAPER-MAKING MACHINE

From the Jordan engine the pulp is passed on into the Fourdrinier
machine, which we are now ready to investigate. The principal element of
this machine is a traveling belt of copper wire gauze which takes the place of
the screen or sieve used in the hand process. To confine the pulp to the belt
there are two endless bands of rubber, known as “deckles,” along each edge
of the screen, which travel with the screen. To insure proper interlacing of the
fibers, as in the hand process, the screen is shaken laterally at the rate of
about 300 vibrations per minute.
The fluid pulp enters the machine through a flow box, where a constant
hydraulic head is maintained, so as to preserve a uniform discharge to the
wire gauze. The milky stream issues through a narrow opening in the flow
box, known as a “slicer.” This may be adjusted to alter the width and also the
thickness of the stream. No one would suspect from the appearance of the
milky fluid that it is filled with fibers, but a microscopic examination of a
drop of the thin liquid shows that it is filled with tiny particles floating in the
water like logs in a river. It is interesting to watch this stream, as it passes out
upon the screen, change magically before one’s eyes, from a milky stream
into solid mass of pulp.

FIG. 71.—DIAGRAMMATIC VIEW OF THE FOURDRINIER PAPER-
MAKING MACHINE
A. Flow Box EE. Pulleys I. The Final Suction Box for Drying
B. Copper Gauze Belt FF. Drums J. Couch Roll
C. Rollers G. Suction Boxes K. Canvas Belt
D. Deckles Confining Pulp H. Dandy Roll

In Figure 71, which is a diagrammatical view of a portion of a Fourdrinier
machine, the flow box is shown at A and the copper gauze belt at B. This belt
is supported on a series of rollers, C. The deckles which confine the pulp
along the margins of the screen are shown at D. These belts travel with the
wire gauze for a certain distance and then pass back over the pulleys, EE,
while the wire cloth passes on and around the drums, FF. As soon as the pulp
flows out upon the wire gauze, the water it contains begins to drain away
through the gauze. But it does not do this fast enough under the mere pull of
gravity and it must be helped by means of suction. At GG there are boxes or
troughs that fit against the under side of the wire gauze. In them a partial
vacuum is maintained by means of suction pumps and a large part of the
water remaining in the pulp is sucked out here. A dandy roll is shown at H,
which presses lightly upon the moist pulp, squeezing out the moisture in it,
and at I there is a final suction box which further dries the web of fibers. It is
the dandy roll that puts a patterned surface on the paper. If the face of the
dandy roll is of finely woven wire cloth with diagonal mesh, a “wove” paper
is produced, while if it is of such surface as to impress parallel lines in the
half-formed paper, “laid” paper is produced. Water marks are also produced
by placing a suitable raised or depressed pattern on the dandy roll, producing
a corresponding thickening or thinning of the pulp. Even after passing the last
suction box, the thin web of paper is still very wet and so flimsy that it cannot
be handled. Right here comes the most delicate part of the whole process.
The web must be picked off the wire cloth and carried across a narrow gap to
a felt belt which conducts it through another set of rollers, A felt-covered roll,

J, known as a “couch” roll, presses down upon the web and the latter clings
to the felt in place of the wire cloth which passes down around the roller F. In
starting a web of paper very skillful manipulation is required to transfer the
web from the couch roll to the felt belt, but after it has once bridged the gap it
has enough tensional strength to pull itself across the gap. The felt belt carries
the web through a pair of heavy rollers which press out more of the water.
Because the paper passes through the rolls with the felt belt it receives an
impression from the felt on the under side. This is now corrected by running
the paper through a second pair of rolls in the reverse direction, and on a
second felt belt, so that both sides of the paper receive the same impression.
From here on the paper passes through a long series of steam-heated drying
rolls and emerges eventually as a perfectly dry sheet.
Our largest Fourdrinier machines make a web 200 inches wide and they
can be run at a rate of 800 feet per minute, or more than nine miles per hour.
The paper is made in lengths eight miles long, which are wound up into rolls
to be fed into the huge printing presses of our metropolitan newspaper plants.
The difference between the making of news print and finer papers lies
chiefly in the quality of pulp used and the quantity of clay and sizing added.
After the finer grades have issued from the drying rolls, they are put through
calenders to give them a glazed surface. This consists virtually in ironing the
paper between smooth rolls of iron on one side and compressed paper or
cotton on the other. Just as in ironing clothes, the paper must be moistened
before being ironed and steam is used to supply the necessary moisture. In
some cases a high glaze is given to one side only of the paper by means of
friction. The paper passes between two rollers of different size. The smaller
one travels faster than the larger one and consequently it slips on the paper,
giving it a very smooth surface.

THE CYLINDER MACHINE FOR MAKING PAPER

There is another type of paper-making machine which is used for coarse
papers, pasteboard, etc. This is known as a cylinder machine. The wire gauze
is formed into a cylinder which revolves in the liquid pulp. A slight suction is
maintained in the cylinder which causes the water to flow in through the
gauze; leaving the fiber drained on the surface. The cylinder revolves,
carrying the drained pulp on its surface until it encounters a felt roll that picks
off the web and carries it to the pressing and drying rolls. One disadvantage

of this type of machine is that the cylinder in dragging the drained pulp
through the water causes the fibers to be combed in a direction parallel to the
run of the paper web, so that the paper, while strong in the direction of its
length, is comparatively weak in the transverse direction. This is corrected to
a certain degree by the use of “riffles” or devices that produce eddies which
disturb the even flow of the pulp.
In the making of pasteboard, a number of cylinders contribute their webs
to form a single sheet of several plies.

CHAPTER XIX

TYPESETTING AND PRINTING MACHINERY

“W
HO WON the war?” The question immediately brings forth
numerous contenders who claim the honor, respectively, for
the aviator, the chemist, the engineer, the mechanic, the
farmer, the shipbuilder, etc. As a matter of fact, all these and
many others as well were invaluable contributors to the final success, and
“there is glory enough for all.”
The question, “What branch of technology or what branch of machinery
has done most for civilization?” finds a similar division of opinion, with
partisans in favor of the steam engine, machine tools, electrical machinery,
iron manufacture, paper making, printing, etc. Again, it is clearly evident
that all have been most valuable contributors and none may carry off all the
honors. However, partisans of the printing press are entitled to place that
machine among the foremost because it has certainly been most useful in
preserving and disseminating all classes of knowledge and in promoting the
progress of civilization.

EARLY CHINESE PRINTING

It is hardly necessary for us to refer to Johann Gutenberg’s invention in
1436 of separate type for each letter. Many centuries before that the Chinese
had made wood engravings of complete pages and printed them on paper.
Their method was to prepare an ink copy on a sheet of paper and then
transfer the copy by pressing the paper on the wood before the ink was dry,
after which they carved away all the surface except those parts which were

inked. This gave them a reverse plate from which any number of copies
could be printed. The invention of individual type which could be used over
and over again for setting new copy was a marked improvement over the
Chinese system.

DEVELOPMENT OF PRINTING PRESSES

The primitive screw press saw little improvement except in minor
details down to the end of the eighteenth century. Then steam began to take
the place of hand power and the idea was conceived of using a rotary
cylinder in place of a flat press. The types were tapered so that they could
be fitted about a cylinder. The paper was fed between the type cylinder and
a soft impression cylinder faced with leather. The ink was applied to the
type by means of a roller which was fed by an inking apparatus.
In 1814 two rotary presses were installed in the offices of the London
“Times,” making it possible to turn out that newspaper at the marvelous rate
of 11,000 impressions per hour. In this country, Richard Marsh Hoe
invented a machine in which four, six, eight, or ten impression cylinders
operated on a single form of type, thereby increasing the output of the press
correspondingly. The first machine, a four-impression cylinder press, was
used by the Philadelphia “Ledger” in 1846, and it printed 8,000 papers per
hour.
Next came the “perfecting” press that printed on both sides of the paper,
and then came the continuous web press, in which the paper was fed from a
roll as a continuous sheet and, after receiving the type impression, was cut,
folded, and delivered as a complete newspaper.

THE STEREOTYPE PLATE

Meanwhile stereotyping was introduced into newspaper printing. In
stereotyping an impression in plastic material is made of the type face and
then a casting is made from this impression which, of course, exactly
duplicates the type face. The type is thus relieved from wear in the press
and it is immediately released for use in setting up other copy while the
printing is done from the stereotype plate. While the use of stereotyping in
book printing dates back to the eighteenth century, it was not thought

practicable for newspaper printing because of the length of time taken in
making the plate, but in 1861 papier-maché was introduced as a matrix
material and a system of rapidly drying the mold was developed so that a
plate could be cast in a comparatively short time; furthermore, impressions
could be made from a flat face of type and then the mold could be bent so
as to make curved stereotype plates for use on the cylinder presses. In
newspaper work it takes but five minutes to make a stereotype plate.
Stereotype metal does not stand the wear of printing very long and the
plates must be renewed from time to time. This fits in well with newspaper
requirements because clean cut work is not called for, and as the news
keeps coming in new editions must constantly be printed, which means that
new plates must be made from time to time. For the finer printing of
magazines and books, copper-faced electrotype plates are used in place of
the soft stereotype plates of newspaper printing.

MODERN NEWSPAPER PRESSES

A modern large newspaper press is a bewildering sight to behold; there
is such a vast number of rolls and cylinders, and the web of paper moves so
rapidly. But, after all, the machine is multiplex rather than complex. It
consists of a large number of printing cylinders, all operating in a single
frame. Take, for instance, a double-octuple, color-combination press. It
consists really of two separate presses, each operating on four webs of
paper that feed from opposite ends toward the middle. There are two type
cylinders for each web, one for each side of the paper. Each cylinder is long
enough to take four stereotype plates side by side, and since each plate
extends but half way around the cylinder we have eight pages printed on
each side of the web. This makes sixteen pages per web or sixty-four for
each half of the machine, giving a total of 128 page impressions at each turn
of the cylinders. It is seldom that a 64-page paper is required, hence the
webs are slit in two by a revolving knife blade and each section of the press
has two folding mechanisms so that two sets of 16-page papers are printed,
folded, and delivered by each section. Arrangements are provided whereby
the product may consist of 32-page papers. The papers are delivered by a
traveling conveyor and every fiftieth paper is pushed out ahead of the others
so as to provide a simple method of keeping count of the product.

PRINTING 240,000 PAGES PER HOUR

The cylinders turn at the rate of 300 revolutions per minute which
means that the paper runs through the machine at nearly 14 miles per hour.
Summing up all the webs we have a total consumption of 108 miles of
paper per hour. The paper is 6 feet wide and the weight of paper in an
hour’s run is about 18 tons and the hourly production is 150,000 sixteen-
page papers. When color is used, the press will deliver 50,000 24-page
papers per hour with the two outside pages printed in three colors and
black. The course of the color printed web must necessarily be different
from that of the plain black printed web. It must pass through a number of
printings; and to prevent the moist ink from transferring to the impression
rolls and from them back to a succeeding page, thus soiling or blurring the
impression, an extra roll of thin paper is passed between the printed web
and the impression cylinders. This acts in a measure as a blotter. The offset
paper is taken up on a roll and used over and over again. It is used not only
for color work, but also when fine half tone engravings are to be printed so
that a cleaner impression may be obtained.
The inking system of printing press is very elaborate. It is highly
essential that the ink be spread upon the type surface in just sufficient
quantity to be picked up by the paper and that the ink be uniformly
distributed over the whole surface. There is an ink reservoir and a set of
inking rollers for each cylinder. The reservoir consists of a trough running
the whole length of the cylinder. At each turn a revolving roller dips into the
ink and transfers a thin film of ink to a series of small rollers. These are
grouped about a large roller to which they deliver the ink. The small rollers
have an axial reciprocating motion whereby the ink is uniformly spread
over the large roller. The latter transfers its thin coating of ink to a pair of
rollers known as “form rollers” and these in turn deliver the ink to the
printing cylinder.

A SEA CAPTAIN’S CONTRIBUTION

The folding mechanism of a printing press is interesting. The paper is
first fed over a wedge-shaped form which folds the paper lengthwise and
then it is given a cross-wise fold. Curiously enough the folding mechanism
for printing presses was first invented by a Yankee sea captain, named

Cromwell, who could not read a drawing but developed his invention by
whittling out wooden models. He also contributed other valuable
improvements for the printing press worked out in the same primitive way.
The rotary press was evolved especially for the printing of daily papers
and for a long time magazines continued to be printed on flat-bed presses.
But as the circulation of magazines grew into the hundreds of thousands it
became necessary to build high speed presses to turn out these large
editions. Accordingly rotary machines were constructed similar in design to
newspaper presses, but with refinements to enable them to produce the
better class of work required of magazine printing. Although there are many
magazines still printed on flat bed presses, particularly those which publish
small editions of less than a hundred thousand, all the big national weekly
journals and monthly magazines are printed on rotary presses and some of
them even use web presses.

GATHERING AND BINDING MAGAZINES

When a newspaper leaves the press it is folded, cut, and ready for the
news stand. Not so with the book and magazine press. There are too many
pages to be handled by a single press, and, furthermore, the pages must be
bound together. Some large magazines contain regularly more than 500
pages and occasionally they will run over a thousand pages. Obviously no
single press could handle so many pages and it takes the product of many
presses to make up a single copy. Each press prints what is known as a form
or signature and these signatures from the different presses are then
gathered, wire-stitched, and bound into individual copies. There are
machines which will do this work of gathering and binding at the rate of
sixty 1,000-page magazines or catalogues every minute. The machines are
adjustable for pages of different dimensions. The forms may consist of four,
eight, sixteen, or thirty-two pages. A separate compartment is provided for
each signature. A large machine will handle thirty-six 32-page signatures.
The compartments are kept supplied by an operator, there being usually six
compartments for each operator to attend to. The bottom signature in each
compartment is brought into position by a suction device which seizes the
signature and draws it out, depositing it in a steel trough. Here a belt
conveyor moves the signature along at the right speed to carry it before the
next compartment just as a signature is being withdrawn therefrom. Thus

the magazine or book is progressively built up and the signatures reach the
end of their course properly assembled. A very delicate adjustment is
provided to insure the proper adjustment of signatures. The grippers are
adjusted to receive signatures of a certain thickness. If the operator should
make a mistake and put a signature of a wrong size in the compartment the
whole machine would come to a standstill. The adjustment is so delicate
that even a variation of a single thickness of paper is enough to operate the
stop mechanism. Each assembly of signatures as it reaches the end of the
trough is squared up and then bound with wire stitching. From this point it
moves on to receive its cover. A thin coating of hot glue is applied to the
rear edge of the signatures. The cover is automatically applied and firmly
pressed into place. The finished book is then carried on out of the machine
and deposited neatly on a pile of previously bound books. To operate such a
machine there are required one chief operator and an assistant and six girls
to feed the signatures to the compartments.

SETTING TYPE BY MACHINE

The publication of a modern daily newspaper with its many special
editions would be well nigh impossible if we still had to depend upon hand
setting of type. Tens of thousands of type characters are required to make up
a single newspaper page, and although skilled hand compositors work with
extreme rapidity it would take a large corps of men to set type for even a
small newspaper in the short time available. Speed is of prime importance
in newspaper work and the task of handling thousands of little pieces of
type metal and arranging them correctly into words and sentences was long
recognized as a serious handicap, but the problem of doing this work by
machine was by no means simple one and baffled inventors for years. One
of the principal difficulties lay in the size and shape of the type and another
was that of justifying the lines, that is, providing just the right width of
spaces between words to fill out the lines completely so that they would all
be of equal length, giving a straight instead of a ragged margin to the
column. After that came the problem of redistributing the type.
The first really successful composing machine was the invention of
Ottmar Mergenthaler in 1888. Mergenthaler overcame the difficulties that
had balked other inventors by attacking the problem from a radically new
angle. Instead of setting precast type, his machine cast its own type from a

set of matrices. By operating a keyboard, the matrices were assembled in a
line which was justified automatically after the line was composed and then
the whole line of type was cast in a single slug. Hence his machine earned
the name “linotype.” Then the matrices were returned automatically
distributed to the proper channels of the matrix magazine ready to be used
over again for succeeding slugs.

THE LINOTYPE MATRIX AND SPACE BAR

FIG. 72—A LINOTYPE MATRIX

A picture of a linotype matrix is shown in Figure 72. It is a plate of
brass formed with ears A at the four corners. The type mold is shown at B
and of course the thickness of the matrix varies with the width of the type
letter it is designed to cast. In the top of the matrix there is a V-shaped slot
C formed with teeth which are designed to engage grooves in a V-shaped
bar over the matrix magazine. The teeth on the matrices are variously cut
away and serve as keys to the different channels of the magazine. There is a
different combination of teeth for each letter of the alphabet and all matrices
of the same letter have the same combination of teeth. The teeth on the
distributing bar are also cut away according to various combinations. After
the line has been cast the matrices are all raised by their ears and fed one by

one upon the distributing bar. Each matrix moves along until it arrives over
the channel it is designed to enter when it comes to a gap in the teeth of the
bar that are supporting it and drops into the magazine. Although there are
but seven teeth on each side of the V-shaped bar, there are more than
enough combinations possible to provide a characteristic one for every key
of the keyboard. A matrix always has at least one pair of teeth in
engagement with the bar until it reaches the gap that lets it fall into its own
special channel of the magazine. The number of matrices of each character
varies with the normal frequency of use of that letter. For instance, the letter
e is very commonly used, and there must be many more e matrices than z
matrices, but in any case the number need not be very large because the
process of casting a line and redistributing the type does not take very long
and the matrices are soon back in the magazine ready to be used over again.
The casting and distributing operations are entirely automatic and while
they are in process the compositor is setting a new line.
The method of spacing which was a later development of the linotype is
also very ingenious. The compositor does not have to bother with the width
of spaces required to fill out a line. He merely touches the space key at the
end of each word and and a space bar drops into place. Each space bar is
formed of a pair of wedges and after the line has been assembled the space
bars are automatically expanded to fill out the line completely by
mechanism which holds down one wedge member (A, Figure 73) and slides
up the other (B).

INDIVIDUAL TYPE CASTING AND COMPOSING

FIG. 73.—A LINOTYPE SPACE BAR

The difficulties of casting the linotype slug proved a serious handicap in
the earlier days of the linotype. The product of the machine could not
compare in quality with precast hand-set individual type, although it served
very well for newspapers; but the machine is now so far perfected that it is
widely used for magazine and book composition. However before this stage
of perfection was reached the demand for a machine that could do a higher
grade of work led to the invention of another machine known as the
“monotype.” The monotype consists actually of two machines, one of
which is operated by a compositor and the other operated entirely
automatically by the product of the first machine. The compositor operates
a keyboard and thereby cuts perforations in a long strip of paper. These
perforations are arranged in characteristic groups one for each key. The
perforated paper is then run through the second machine and in accordance
with the various perforations the separate types are cast and assembled into
justified lines. Air flowing through the perforations operates a pneumatic
mechanism which brings the proper molds into position and casts the
separate types. The method of justifying the lines is very interesting. As in

the linotype the operator merely touches a space key at the end of each
word, but at the end of the line the mechanism automatically estimates the
spaces to be filled and divides this by the number of spaces so that a
characteristic group of perforations is punched when the compositor shifts
to the next line. In the casting machine the paper ribbon runs through
backward and the space group of perforations is encountered before the line
is cast. This automatically adjusts the mechanism to cast spaces of the
requisite size to fill out the line exactly.

WRITING BY MACHINE

In one sense we have taken up the various machines employed in
printing in reverse order. Of course the first machine used is the typewriter,
after which comes the composing machine, and finally the press.
It was in 1866 that two inventors, C. Latham Sholes and Samuel W.
Soule, undertook to make a machine for printing numbers in serial order
upon the pages of a blankbook. Carlos Glidden, another inventor, who was
engaged in developing a spading machine designed to take the place of a
plow, saw their work and suggested that they make their machine write
letters and words as well as numbers. The three combined and proceeded to
evolve the new machine. By the end of the summer of 1867 they had
produced a typewriting machine that could be operated fairly rapidly and
that produced fair work. It was one of the letters written by this machine
that brought James Densmore into the enterprise. He furnished the money
needed to improve the crude typewriter and make it a commercial machine.
Many models were built but nothing was produced that seemed good
enough for commercial production. This development work was too slow
and discouraging for Soule and Glidden and they dropped out, but Sholes
inspired by Densmore persevered until at last in 1873 he had produced a
machine which he could offer for manufacture. The typewriter was then
taken to the Remington factory at Ilion, N. Y., and the next year it was
placed on the market and began its public career.
Such is the story of the early development of the typewriter. It has
become so widely used and is so indispensable a part of the business office
that it arouses the utmost astonishment to learn that there still are a few old-
fashioned houses so conservative and so far behind that they continue to
write their business letters with the pen. So common a machine, it is hardly

necessary for us to describe in detail except to mention two steps in the
development of the machine, namely the arrangement of the type bars
whereby the typewriting is visible to the typist, and secondly the effort to
overcome noise by limiting the stroke of the type bar and making it impinge
upon the paper with a pressure stroke rather than a hammer blow.
A recent development is the “stenotype,” a small machine which prints
shorthand characters, thus expediting the taking of rapid dictation.

CHAPTER XX

CAST IRON, WROUGHT IRON, AND STEEL

I
T USED to be that wars were fought for gold, but nowadays the
possession of rich iron mines is enough to arouse the cupidity of
neighboring nations less favored by nature. In fact, even though an ounce
of gold is worth twice as much as a ton of iron, the value of the iron we
dig out of the earth each year is far greater than that of gold. When that rough
ore is converted into iron and steel and then into thousands of useful articles,
its value mounts so high that it cannot be estimated. The qualities of iron and
its alloys are so excellent and so varied under different treatment that this
metal may truly be said to form the foundation of all our mechanical
progress. On the one hand it spans our wide rivers, carries the burden of
heavy freight trains, or, in the form of armor plate, resists the terrific impact
of high-powered shells; on the other hand the same metal, spun into a hair
spring, governs the ship’s chronometer, or, in the compass, points a trembling
finger to guide the navigator on his course.

IRON IN ANCIENT DAYS

The first use of iron in the service of man dates far back into the ages. An
iron tool was found in the pyramid of Kephron which must have been used
3,500 years before Christ. However, because of the difficulty of working it,
iron was not extensively employed except for swords and cutlery. The
conversion of iron into steel and the tempering of steel blades grew to be an
art which gave Damascus and Toledo a world-wide reputation that dates back
over a thousand years.

The ancients used to smelt their iron ore in what was known as a Catalan
forge because of its extensive use in Catalonia, Spain. Whether the forge was
invented there or not we cannot say. Similar forges have been found in India
and other widely remote places. They comprised an inclined tray leading to a
pot which formed the furnace and in which a charcoal fire was kindled. The
ore and charcoal were placed on the tray and from time to time were raked
down into the furnace and air was forced into the bottom of the furnace by
means of bellows. In an improved form of the Catalan forge air was furnished
by means of an air compressor operated by a stream of water. This has
already been referred to and illustrated on page 90. Limestone served as a
flux to melt the earthy matter. The iron obtained from these primitive
furnaces was not heated sufficiently to flow as a stream, but was merely
reduced to a pasty mass which was then hammered into shape by the
blacksmith. Ten or twelve pounds of metal per day was considered a fair
output for one of these forges.

DISCOVERY OF COKE

It was not until the middle of the 14th Century that a blast furnace,
crudely similar to those we have to-day, was first built and with it a
temperature was obtained that was high enough to turn the metal into a liquid
which could be cast in molds. Charcoal continued to be the fuel used until
about four centuries later, when Abraham Darby discovered that by baking
coal to remove its free gases, he could produce a new fuel known as coke
which was a good substitute for charcoal. This gave a wonderful impetus to
the iron industry in England where there were ample deposits of coal adjacent
to the iron mines. Shortly after that, Mr. Henry Cort of Gasport, England,
invented the processes of puddling and rolling the product of the blast
furnace, thus converting the iron into a tough, malleable metal.

ALLOYS OF CARBON AND IRON

We must pause here to learn the difference between cast iron, wrought
iron and steel. Iron, as we know, has a high affinity for oxygen. When
exposed to air and moisture it oxidizes, rusts very quickly. The iron we find
in nature is largely oxidized. In other words, it is rusty. It is also found in
combination with other elements as well. The object of putting iron ore
through a furnace is to rid it of oxygen and this is most readily accomplished

by melting it in a carbon fire. The highly heated carbon combines with the
oxygen and passes off as carbon dioxide and carbon monoxide gas. But a
certain amount of carbon unites with the iron and it is this alloy of carbon and
iron that makes cast iron so stiff and brittle. The less carbon present the softer
is the metal and pure iron is very ductile.
It was to rid cast iron of its carbon content that Cort invented the puddling
process. As the metal came out of the blast furnace it ran into a
“reverberatory” furnace where, without coming in contact with coke or other
carbon fuel, it was exposed to flames from an adjoining furnace which
burned out the carbon, and then the carbon-free iron was cast into large
pieces known as blooms which were hammered to rid them of slag. The final
product was known as wrought iron. Wrought iron then differs from cast iron
in having no carbon. Steel, on the other hand, stands half way between
wrought iron and cast iron in having a small percentage of carbon. How steel
is made will be described later.

MECHANICAL HANDLING OF ORE

Of course machinery plays a large part in the modern iron industry. It
would be an endless task even to load one of the big blast furnaces by hand
and then the enormous output of molten metal—40 tons for every pound
produced by the old Catalan furnaces—could not be handled without
ponderous machines whose huge arms and fingers are not scorched and
blistered by the intense heat. Along the Great Lakes vast loading machines
fill the holds of ore vessels and at the plant there are enormous unloading
machines that travel on rails. These have long bridgelike arms that reach out
over the ore boat and drop huge clam-shell buckets into their holds. The
buckets quickly unload the boats and dump the ore on shore where other
buckets pick up the ore, carry it back and pile it up in big heaps that look like
mounds of reddish earth.

THE MODERN BLAST FURNACE

Blast furnaces are towering cylindrical structures of steel lined with fire
brick. They are loaded from the top with alternate layers of coke and ore.
Limestone also is added to act as a flux for the earthy matter, as explained
above. Running around the furnace near the base there is a large pipe known

as the “bustle” pipe. Through this air is fed to a set of “tuyeres” which lead to
the base of the furnace and admit blasts of air requisite to maintain
combustion at an intense heat. The gases of combustion are not allowed to
escape freely into the atmosphere. The top of the furnace through which the
ore and fuel is admitted is closed by an air lock and the flaming hot gases are
led into “stoves” where they give up a large part of their heat to preheat the
air which is pumped to the blast furnace. The gases being mainly composed
of carbon monoxide are further combustible and may be used for heat, light,
and power purposes. In fact, they are commonly used to drive the air
compressors which feed the blast furnaces.
The blast furnace has two openings, one above the other. Through the
upper one slag is drawn off while the molten iron which trickles down and
collects at the bottom of the furnace is tapped off through a hole near the base
of the furnace. The fiery stream pours out into a lot of small trough-shaped
molds and is thus formed into “pigs.” These pigs are all connected to the
main body of the metal stream and must be broken off. To save the time of
cooling and of breaking off the pigs a machine is used which consists of a
series of molds connected to form an endless belt. The molten iron is poured
into these molds which in their course dip into a trough of water. Here the
iron is cooled and solidified. The molds then run up an incline and finally
dump the pigs directly into railway cars which haul them away.

BURNING OUT THE CARBON

The production of steel economically and on a large scale dates back to
the inventions of Henry Bessemer. While searching for an improved method
of making big guns, Bessemer hit upon the idea of forcing a blast of air
through the molten iron and thus burning away carbon, silicon, and
manganese in the cast iron. No fuel was supplied except the carbon and
silicon in the iron itself. In burning out this carbon sufficient heat was
generated to keep the metal fluid.
When Bessemer made the announcement of his new process before the
British Association in 1856, his paper met with skepticism, but he was able to
demonstrate by actual experiment that cast iron could be converted into
malleable iron in this way. However, when several firms operating under
licenses from the inventor endeavored to reproduce his experiment on a
commercial scale they were unsuccessful, and after costly experiments the

process was given up as a failure. Bessemer, however, persisted in his efforts
and succeeded eventually in producing malleable iron of a quality equal if not
superior to that on the market. But iron makers after the failure of the first
experiments would have nothing to do with the new process until Bessemer
began to turn out quantities of iron at $100 a ton below the prevailing market
price. Then iron makers woke up and Bessemer had no difficulty in placing
his process with numbers of firms on a very profitable royalty basis.
This process pertained to the making of iron and not steel. When
Bessemer tried to produce steel he was confronted with serious difficulties.
The steel he obtained was very brittle. He tried purer ores with little better
success. Then a solution of his problem was offered by Robert F. Mushet,
who discovered a compound which would be added to the molten metal to
purify it. This compound which is known as “spiegeleisen” is composed of
iron, carbon, and manganese. It removes the oxide of iron and the sulphur
and regulates the amount of carbon in the steel.
A Bessemer converter furnishes by far the most spectacular operation in
steel manufacture. The converter consists of a large bottle-shaped vessel lined
with refractory material. In the bottom of the vessel there are openings
through which the air blast is admitted. The molten metal is poured into the
flask and then the air blast is turned on. The metal begins to boil violently. A
dazzlingly brilliant blast of flame and sparks comes roaring out of the mouth
of the converter. Bubbles of metal are thrown high into the air where they
burst into showers of sparks. The effect is similar to that of a volcanic
eruption. In from ten to twenty minutes the eruption subsides and then a
quantity of spiegeleisen is added. The converter is mounted on trunnions so
that when the operation is completed the vessel is tilted over and the charge
of molten metal now converted into steel is poured out.

OPEN HEARTH FURNACES

MOLTEN METAL FROM A BLAST FURNACE

BESSEMER CONVERTER BLOWING AIR THROUGH A MASS OF
MOLTEN IRON

A STEEL BEAM PASSING THROUGH THE FINISHING ROLLS OF A
STEEL MILL

FIG. 74.—SECTIONAL VIEW OF A REGENERATIVE OPEN-
HEARTH FURNACE

While the Bessemer converter provides a very economical and
expeditious method of converting cast iron into steel, it is difficult to regulate

the carbon content with great accuracy and hence the use of the open-hearth
furnaces which furnish a slower method of burning out the carbon. Figure 74
is a diagrammatic representation of such a furnace. Below the hearth of the
furnace there are two pairs of chambers, A, B and C, D, filled with a
checkerwork of bricks. Gas is passed through one chamber A, and air through
the other B, and they combine to form a very intense flame above the hearth
E in which the metal is placed. The burnt gases pass over and through the
other pair of chambers, C, D, on their way to the stack. By this means the
bricks in the latter chambers are raised to a white heat. Then the process is
reversed; air flows through the hot checkerwork of bricks in the chamber C
and gas through the hot checkerwork in chamber D, and after combustion in
the furnace the burnt gases are drawn through the bricks of the first pair of
chambers. By alternating the direction of flow the air and gas fed to the
furnace are always preheated by the stored-up heat of the previously burned
gases. While it takes but a few minutes to convert cast iron into steel in the
Bessemer converter, the open-hearth process occupies from eight to twelve
hours.
The steel produced in the open-hearth furnaces is poured into ingot
molds. These are approximately rectangular in section and slightly larger at
the bottom than at the top. They are open at the top and bottom, but at the
bottom rest upon a base plate. As soon as the steel has hardened the plunger
of a stripping machine holds down the glowing ingot while a pair of hooks
lift off the mold, leaving the ingot resting on the base plate.

ROLLING INGOTS INTO RAILS

In the manufacture of railroad rails the ingots are placed on a traveling
“table” consisting of a series of rapidly turning rollers. These carry the ingot
to a pair of large steel rolls between which it passes. The rolls compress the
ingot slightly and it is automatically turned over and passed through a second
pair of rolls. After passing through four “stands” of rolls, turning over
between each stand, it is considerably reduced in cross-sectional area and
correspondingly lengthened. It is now termed a “bloom.” The bloom goes
through a series of rollers which gradually reduce its section until it is some
forty feet long. Then it is cut in two and each section passes through other
rolls, until finally it is reduced to the required rail section. Each section is
then about a hundred and twenty feet long and the glowing writhing rail
passes on to the saws where it is cut into ten-yard lengths. A similar process

is employed in rolling other forms of rails and in making steel plates and
sheets.

STEEL FOR BIG GUNS

The largest machines employed in the steel industry are those used for the
manufacture of armor and big guns. A modern large high-powered gun is not
a single solid casting or forging, but is made up of a series of steel tubes that
are shrunk one upon another so that the inner tube is compressed. The reason
for this is that the explosives used are so powerful that they would expand the
inner tube or lining of the gun beyond its elastic limit and in that way enlarge
the bore. By having it compressed to start with it can expand farther without
exceeding the elastic limit. This expansion takes place so suddenly that the
lining rebounds or returns to its original dimensions before the outer tubes
have felt the full pressure and they too are thus prevented from being
expanded too far. In some cases the compression is effected by winding the
gun with a heavy wire of rectangular cross section.

SQUEEZING OUT THE “PIPES”

Steel for guns and armor is made in the open-hearth furnace where the
quality of the metal may be regulated to a nicety. Gun tubes are cast in
vertical molds and during the cooling of the ingot it is subjected to pressure
so as to prevent segregation and the forming of “pipes.” Pipes are cavities
that are liable to form in the center of the ingot due to contraction during
cooling. Steel, as we have learned, is not pure iron, but an alloy, and the
various constituents have different temperatures of solidifying, consequently
they exhibit a tendency to segregate. It is to overcome such tendencies that a
so-called “fluid” compressor is used. This is virtually a hydraulic press with a
plunger that bears down on the fluid metal as it is solidifying. Modern big
guns are enormously large. A sixteen-inch 50-caliber gun, for instance, is
nearly seventy feet long, consequently the ingot must be even longer than this
and the fluid compressor for so large a piece must be correspondingly
powerful. After the ingot has been cast and cooled, the ends are cut off and it
is bored to form a tube. Then it is placed in a furnace and raised to a white
heat, after which a bar or mandrel is inserted in the bore and the tube is
placed under the hydraulic forge press. This is a very powerful machine with
an immense hammer that is actuated by hydraulic pressure. The stroke of the

hammer is carefully regulated so that the forging as it is turned in the forge is
subjected to equal blows. In the forge the tube is roughly formed to the
dimensions it is eventually to have when finished. The process of forging
subjects the metal to strains which must be relieved and so the tube has to go
to the annealing oven where it is raised to a temperature which destroys
crystallization. In this oven it is allowed to cool very slowly, letting the
molecules of the metal adjust and rearrange themselves. When the
temperature of the tube has been lowered to a certain point it is taken out and
plunged into a bath of oil. This sudden cooling tempers the metal, giving it a
high degree of elasticity and tensile strength. Again the tube must be annealed
to relieve it of any strains occasioned by the tempering, and then it goes to
the shop to receive its finish boring and turning.
The process as here briefly described seems simple enough, but we must
not forget the enormous size of these pieces and their tremendous weight.
They would be difficult enough to handle when cold, but much of the work is
done while the pieces are at a white heat so that the men who control and
operate the machinery that handles the big forgings must keep their distance.
The casting, annealing, and tempering operations are performed with the
piece in vertical position, and lofty machines and cranes are required to deal
with these tall castings. A visit to a plant which manufactures big guns is
bound to impress the visitor with awe and give him increased respect for the
men who are able to handle such huge masses of metal and also for the men
who have conceived and developed such gigantic operations.

CHAPTER XXI

ANIMATED MACHINERY

I
N MARKED contrast to the massive machinery and apparatus described
in the last chapter, and fully as wonderful, is a class of machinery to
which we might apply the term “animated.” By this we do not mean
manikins or toys, but certain higher types of machines which seem to be
possessed of powers that we should expect to find only in living beings—
machines that have a sense of touch, sight, and hearing—machines that will
reason out a mathematical problem; that will talk; that have the equivalent of
a memory. In this broad classification we may include such widely different
machines as the motion-picture camera and projector, and that mysterious
mechanism which seems animated with strange powers of its own—- the
gyroscope.

MATHEMATICAL MACHINES

Adding, subtracting, multiplying, dividing, and the working out of
complex mathematical problems by machine seems wonderful until we stop
to reflect that mathematics is the most precise and mechanical of all sciences.
In the simpler forms these machines are mere counting mechanisms in which
the counting is done very rapidly by the aid of intermeshing gears. The
adding machine is in no sense possessed of any reasoning power, but blindly
obeys the simplest of mechanical laws. There are rows of wheels with
numbers running from 0 to 9 printed on their peripheries. One wheel
represents “digits,” the next “tens,” the next “hundreds,” etc. The wheels are
interconnected by means of gearing so that when the digits wheel makes a
complete turn, the tens wheel makes 1-10th of a turn, and when the tens

wheel completes a rotation the hundreds wheel makes 1-10th of a turn. Keys
numbered from “0” to “9” are provided, which respectively turn each wheel
through angles from 1-10th to 10-10ths of a rotation. Thus suppose the digit
wheel has already been turned through 9-10ths of a rotation and registers the
figure “9,” and the “8” key is depressed, the wheel will be given an additional
turn of 8-10ths of a rotation and will register the figure “7,” but the tens
wheel to the left will also move through 1-10th of a rotation, so that the two
wheels will register “17.” Such is the underlying principle of the adding
machine, but various refinements are added. For instance, the numbers that
are being added are recorded in print, and the total sum of the numbers is not
printed until the operator desires to foot up the column.
More complicated, of course, are the mathematical machines which work
out involved equations, but they are all based on simple mechanical
operations. In the Weather Bureau at Washington there is a tide-predicting
machine, which has been called a “great brass brain.” Its brass gears may be
set to allow for all the varying factors of apparent solar and lunar motions,
and they will work out the tide for any past or future data in a few moments,
solving mechanically a mathematical problem that, by hand, would take
hours and hours of weary figuring.

HEARING AND TALKING WITH A MECHANICAL “EAR”

It was in 1877 that Edison startled the world with a machine that could
actually talk. Others had been working on this problem for years, but they
had been trying to copy the human mouth and organs of speech. Edison
attacked the problem from a new angle. He was not aiming to produce speech
but to reproduce it. Let the human vocal organs modulate the sound waves so
that they would produce spoken words; he would provide a machine with no
mouth but only an ear and a very retentive memory which would listen to
these sound waves and make an impression of them on its soft tinfoil or wax
brain. Then, at any time by the principle of “reversal,” the record could be
made the transmitter instead of the receiver of sound waves, and it would
actuate the ear so that it would repeat the sound vibrations it had formerly
received. Thus Edison made the ear of his machine serve the double office of
hearing and talking. When Edison’s phonograph was listening it had a sharp
needle attached to the ear-drum or diaphragm of the sound box, which cut a
hill and dale groove in the brain or cylinder record of the machine; when

reproducing, a blunt needle was used which faithfully followed the hills and
dales of the groove without cutting a path of its own.
The next notable improvement in the phonograph was that of Emile
Berliner, who in 1887 invented the laterally vibrating needle which cut a
zigzag groove in the record instead of a hill-and-dale groove. In other words,
instead of having his recording needle move in and out as in the Edison
machine, it moved sidewise. He also invented the flat-disk record, which has
almost completely supplanted the cylindrical record.

MACHINES THAT PICTURE MOTION

In a measure associated with the phonograph is the motion-picture
machine, a machine with an eye and a retentive memory, which records on a
sensitive retina a series of pictures that it is able to reproduce at any time. The
recording of still photographs is remarkable enough in itself, but photography
does not properly belong in a book on machinery. The taking of motion
pictures, however, and the projection of these pictures upon the screen,
involves the use of machinery, and we must refer to these machines briefly,
owing to their widespread use at the present time.
Long years ago it was observed that when a picture is suddenly flashed
before the eye an image is impressed upon the retina, which persists for a
brief interval even after the picture itself has been withdrawn from view. By
preparing a series of pictures of a figure which show it in progressive
positions and flashing these pictures in rapid succession before the eye,
persistence of vision will bridge the gaps between pictures and the figure will
appear to move. This principle was first used as early as 1834 in an ingenious
toy known as “zoetrope,” which consisted of a cardboard cylinder with a
series of pictures drawn on the inner surface. There were slots cut in the
cylinder through which these pictures on the opposite face of the cylinder
could be seen. As the cylinder was revolved the eye caught only momentary
glimpses of these pictures, one after the other, producing a sense of motion.
In 1870, Henry Heyl of Philadelphia prepared a progressive series of
photographs each separately posed before the camera. From these he made
glass positives and projected them on a screen in rapid succession so that the
picture appeared to move. In 1880, Edward Muybridge set up a battery of
cameras and took a succession of instantaneous pictures of a galloping horse.
The shutters were operated by strings stretched across the course and as these

were successively snapped by the horse the pictures were progressively
exposed. Glass positives of these pictures were thrown on the screen by
means of a machine to which he gave the formidable name “zoöpraxiscope.”

INVENTION OF THE PHOTOGRAPHIC FILM

No one at that early date had thought of using anything but glass plates,
and they were difficult to handle, both in the camera and in the projector. It
was not until 1887 that the celluloid film was invented by Rev. Hannibal
Goodwin, and then it became possible for Edison to invent a camera with a
film that was intermittently moved so as to take a series of pictures. From the
negative thus obtained a positive film was then made and placed in a machine
known as a “kinetoscope.” Looking through a peephole in this machine the
pictures were flashed before the eye in rapid succession. Finally, in 1893, C.
Francis Jenkins, of Washington, developed a projector similar to those now in
use by which the pictures could be thrown on a screen. Thus was born the
motion-picture industry which has taken such a strong hold on the public.
It is now possible to project pictures in their natural color so as to add to
their realism, but one more step is needed to give a sense of real life. The
figures on the screen must talk as well as move. Efforts to combine the
phonograph with motion pictures have so far been only partially successful.
Perfect synchronism is very difficult to obtain, but it is highly probable that
obstacles which hitherto have been most troublesome and seemingly
insurmountable will, in time, be overcome. Then the “silent drama” will no
longer be silent and we shall have “animated pictures” that will be really
animated.
In addition to machines that talk we have machines that hear—machines
that will respond to sound waves. A diaphragm flexed by sound waves closes
an electric circuit and starts the operation of a machine. Some toys have been
made which operate on this principle. Experiments have been made with a
typewriter that will respond to a spoken message, but so far they have not
been attended with much success. Boats have been built whose steering gear
may be controlled by sound waves, but as yet nothing of commercial
importance has been developed in machines controlled by sound.

MACHINES THAT SEE

Much more has been done with machines that see. There is a delicate
device known as a “sun valve,” which is used on beacon lights so that as soon
as it grows dark or very foggy the lamp is automatically lighted, and when
the day dawns or light breaks through the fog the light is extinguished. The
sun valve has two rods, one brightly polished and the other a dead black.
Light and its attendant radiant heat waves are absorbed by the black rod, but
are reflected from the bright rod. As a consequence, the black rod grows
hotter than the polished rod and expands. The difference of expansion
between the two rods is utilized to operate a valve which controls the supply
of gas to the lamp. This valve is very sensitive and marvelously responsive to
variations of light.
There is a chemical element called selenium, which is peculiarly sensitive
to light. When light shines upon selenium its electrical resistance is lowered,
and hence it can be used as a light-operated valve to control the flow of
electric current.

A MACHINE THAT READS PRINT

One of the most marvelous machines of the present day is one which will
actually read ordinary printed type, uttering musical sounds that vary for each
letter, so that a blind man after learning this new musical language can read
any book. This machine, known as the optophone, is the invention of Prof. E.
Fournier d’Albe, and was developed to a commercial success last year
(1920). With it blind operators are able to read at the rate of twenty-five
words per minute.
The operation of this wonderful machine can best be understood by
reference to the accompanying diagrams, Figures 75 and 76.

Diagrammatic Arrangement of Optophone.
FIG. 75.—END VIEW OF THE FIG. 76.—SIDE VIEW OF THE
OPTOPHONE OPTOPHONE

There is an electric lamp in the machine before which there is a disk that
is revolved by a small motor. In this disk there are five circular rows of slots
and the light shining through these slots is cut up into five pulsating beams of
light. These beams are brought to a focus in a vertical row upon the type
page. From the paper they are reflected to a selenium cell or bridge. The
selenium bridge forms part of the circuit of a telephone receiver and the
diaphragm is thus made to vibrate at the same frequency as the light beams
do. By varying the number of slots in each row in the disk the beams of light
are given different periods of pulsation or vibration and they produce a sound
chord or “scala” in the telephone receiver. The speed of the disk and the
disposition of the slots is so chosen that the notes produced are G C′ D′ E′ G′
of the musical scale. Only white paper reflects the light beams; the black
surface of the printed type absorbs them. Thus, as the row of beams is swept
across a line of printed matter, the beams will be extinguished in various
orders of succession, or simultaneously in accordance with the shape of the
particular type-character they encounter.
The middle three beams correspond to notes C′, D′ and E′, and play upon
the small letters, while G′ plays up the upper part of capital letters, and G
upon the tails of such letters as y, p, etc. If the scala passes over the letter “V,”

for instance, first the top note G′ is silenced, then E′, D′, C′, D′, E′ and G′ in
succession. This arrangement constitutes what is known as the “white
sounding” optophone, because the full chord is sounded constantly, except
when the type matter is encountered.
To simplify the reading an improved type of optophone has been made,
which is known as the “black-reading” optophone, With this machine there is
no sound produced except when the type is encountered. The letter “V” is
then identified by the sounding, instead of the silencing of the notes G′, E′,
D′, C′, E′ and G′. The letter “A” produces the sounds C′, D′, DE′, DG′, DE′,
D′ and C′. This result is obtained by using two selenium bridges, as shown
better in the side view, Figure 76. There is a concave reflecting lens, which
reflects half of the light upon the second cell, known as the balancer selenium
bridge. Electric current passing through the balancer opposes the current
passing through the main selenium bridge, and hence there is silence in the
telephone receiver when the scala passes over plain white paper, but when
type is encountered and certain of the beams are not reflected against the
main selenium bridge the sounds are produced through the balancer bridge.
The success of the optophone leads one to hope that it may be but the
forerunner of a machine that will translate the whole world of light and color
into one of music, and permit the blind not only to read by ear, but also to see
their friends and their surroundings through the sense of hearing. In fact
efforts to make such an apparatus preceded the invention of the optophone.

THE WILLFUL GYROSCOPE

As intimated above, we have included the gyroscope among the higher
type of machines, because it seems possessed of a stubborn will of its own,
and apparently defies the laws of gravity.
There is nothing mysterious about its mechanism. It is merely a wheel
with a heavy rim and with its axis mounted in gimbals, so that it may turn
freely in any direction. The wheel, when at rest, behaves no differently from
any other mechanism. But once the wheel is set to spinning at a high velocity
it seems to acquire marvelous powers and obstinate notions of its own as to
what it will do and what it won’t do. You may lift it, or lower it, or move it
sideways in any direction, and it will not show the least sign of rebellion so
long as the plane of its rotation is not deflected, but attempt to twist its plane
of rotation and it will resist with the power of a giant. The resistance that

even a small gyroscope will develop is astounding. A wheel weighing not
more than 10 pounds may develop so much energy that a man twenty times
as heavy pushing with all his might cannot turn it over. Not only does it resist
the push, but it actually leans back against the pusher. Then it has the peculiar
habit of turning at right angles to the direction in which it is pushed. Suppose,
for instance, the axis of the gyroscope is horizontal and it is resting freely on
a pair of supports, one at each end. Remove one of the supports and the
gyroscope does not fall. To do so it would have to swing around the other
point of support as a center; in other words, the plane of rotation would have
to be turned angularly and such a motion the gyroscope resists. The
unsupported end of the axis dips momentarily under the pull of gravity, but
immediately recovers and actually rises above the horizontal, then it begins to
revolve slowly in a horizontal circle about the supported end of the axis—a
motion which is technically known as “precession”. The pull of gravity
exerted in a downward direction results in a horizontal motion at right angles
thereto. It seems as if the gyroscope was bidding defiance to laws that govern
other objects, but, of course, such is not the case. The gyroscope is as
submissively obedient to the laws of gravity as any other object or machine,
but the forces which act upon it are so complicated that it is difficult for one
to comprehend them without study. In fact, it is almost impossible to explain
the strange behavior of a gyroscope without the use of mathematics that is
too involved to be presented in this book.
Of course, the underlying cause of gyroscopic action is inertia; i. e., the
tendency of a body to retain its state of rest or uniform motion. A bullet is
forced out of a gun by the sudden expansion of gases behind it, but after it
leaves the muzzle and the influence of the gases, why does it keep on
traveling? We may just as well reverse the question and ask why it should
ever stop. Having once acquired a certain velocity it keeps that velocity
because of its inertia or mechanical helplessness, and it would keep on going
forever were it not for the resistance offered by the air and the pull of gravity,
which gradually draws it down to earth. It takes a deal of energy to divert the
bullet from its course. In a gyroscope we have a similar condition.

FORCES DEVELOPED IN A GYROSCOPE

We may conceive of a gyroscope as consisting of a stream of bullets all
tied to a center, so that they fly around in a circle. Any effort to deflect the
bullets out of their course will be resisted by each bullet as it comes to the

deflector. Here each bullet acts individually, but in a gyroscope wheel the
equivalent of the stream of bullets is a solid rim, each particle of which is
rigidly connected to every other particle, and so the whole wheel immediately
feels the deflecting force and resists it. As long as the wheel is maintained in
its own plane of rotation, or moved into parallel planes, there is such a perfect
balance of all forces that no more resistance is offered to the motion of the
wheel as a whole than would be offered by any other object of equal mass.
But when the wheel’s plane of rotation is moved angularly, a complicated
series of forces is developed.

FIG. 77.—SOME OF THE FORCES DEVELOPED IN A
GYROSCOPE WHEN ITS PLANE OF ROTATION IS
SUBJECTED TO ANGULAR MOTION

Some idea of the nature of these forces and why they give rise to
precession may be understood by reference to the diagram, Figure 77. Here
we have a disk with a heavy rim turning on the axis X, X′. At A, B, C and D
are four particles whose flights we are going to consider. Suppose the wheel
to be at rest; then if X, X′ is tilted in the direction of the arrows x x′, the wheel
will turn about the line Y Y′; D will move forward toward D′, and B backward
toward B′, but A and C will remain where they are. Now, suppose, the wheel
to be revolving clockwise, or in the direction A, B, C, D, then the particle A

will pursue a spiral course that will bring it to B′, and C will pursue a spiral
course that will bring it to D′. However, particle D will have an irregular
course, as indicated by the dotted line, starting first to move forward and then
curving back toward A. The same will be true of B, except in the reverse
direction. The course of particles D and B is, therefore, materially different
from that of A and C. Now, the particle D will resist being deflected from its
course and will develop an opposing force represented by the arrow d. A
moment later this is reversed as the particle bends back toward the axis Y Y′,
and we may represent the new force by the arrow d′. It may be proved that
the force d′ is more powerful than that of d. The particle A in the meantime
exerts a force opposing its deflection, which is represented by the arrow a.
On the other half of the wheel there are similar but opposite forces, b, b′ and
c. The sum of these forces gives the wheel a tendency to turn about the axis Z
Z′. To avoid complicating our diagram with too many arrows, we had better
refer to a new diagram (Figure 78) which shows only the resultant of the
forces developed. The application of the forces x x′, which would have turned
the wheel on the axis Y Y′, had it been stationary, have resulted in the
development of forces z z′ at right angles to x x′, tending to turn the wheel
about the axis Z Z′. Now, if we go through the same processes of reasoning as
before, it will be evident that the forces z z′ will result in a third set of forces y
y′ at right angles to z z′ tending to turn the wheel about the axis Y Y′. The
forces y y′ exactly balance the forces x x′, and hence the wheel does not turn
about the axis Y Y′ in response to the original forces, but starts instead to
revolve slowly about the axis Z Z. Because the forces x x′ and y y′ balance
each other, there is no fourth couple developed and hence no opposition to
the forces z z′.