Every-day Science: Volume 6. The Conquest of Nature
by Henry Smith Williams · English · Gutenberg #44502 · 541,677 chars · public domain (US)
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Title: Every-day Science: Volume 6. The Conquest of Nature
Author: Henry Smith Williams
Edward Huntington Williams
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Language: English
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TRANSCRIBER'S NOTES
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[Illustration: A PRIMITIVE USE OF THE ANIMAL MACHINE THAT IS STILL IN
VOGUE IN MANY EUROPEAN COUNTRIES.
(From the painting by J. Didier, in the _Musée du Luxembourg_, Paris.)]
EVERY-DAY SCIENCE
BY
HENRY SMITH WILLIAMS, M.D., L.L.D.
ASSISTED BY
EDWARD H. WILLIAMS, M.D.
VOLUME VI
THE CONQUEST OF NATURE
ILLUSTRATED
NEW YORK AND LONDON
THE GOODHUE COMPANY
PUBLISHERS MDCCCCIX
Copyright, 1910, by THE GOODHUE CO.
_All rights reserved_
CONTENTS
CHAPTER I
MAN AND NATURE
The Conquest of Nature, p. 4--Man's use of Nature's gifts, p.
6--Man the "tool-making animal," p. 7--Science and Civilization,
p. 8--Clothing and artificially heated dwellings of primitive man,
p. 10--Early domestication of animals, p. 11--Early development to
the time of gunpowder, p. 12--The coming of steam and electricity,
p. 15--Mechanical aids to the agriculturist, p. 19--The development
of scientific agriculture, p. 20--Difficulties of the early
manufacturer, p. 21--The development of modern manufacturing, p.
24--The relation of work to human development, p. 25--The decline of
drudgery and the new era of labor-saving devices, p. 27.
CHAPTER II
HOW WORK IS DONE
Primitive man's use of the lever, p. 29--The use of the lever as
conceived by Archimedes, p. 21--Wheels and pulleys, p. 32--Other
means of transmitting power, p. 35--Inclined planes and derricks, p.
37--The steam-scoop, p. 38--Friction, p. 39--Available sources of
energy, p. 41.
CHAPTER III
THE ANIMAL MACHINE
The oldest machine in existence, p. 43--The relation of muscle
to machinery, p. 44--How muscular energy is applied, p. 44--The
two types of muscles, p. 45--How the nerve-telegraph controls the
muscles, p. 47--The nature of muscular action, p. 49--Applications
of muscular energy, p. 52--The development of the knife and saw, p.
53--The wheel and axle, p. 55--Modified levers, p. 57--Domesticated
animals, p. 59--Early application of horse-power, p. 60--The
horse-power as the standard of the world's work, p. 61.
CHAPTER IV
THE WORK OF AIR AND WATER
First use of sails for propelling boats, p. 62--The fire engine of
Ctesibius, p. 63--Suction and pressure as studied by the ancients, p.
64--Studies of air pressure, p. 65--The striking demonstration of Von
Guericke, p. 66--The sailing chariot of Servinus, 1600 A.D.,
p. 68--The development of the windmill, p. 69--The development of the
water-wheel, p. 70--The invention of the turbine, p. 72--Different
types of turbines, p. 73--Hydraulic power and its uses, p. 74--The
hydraulic elevator, p. 76--Recent water motors, p. 77.
CHAPTER V
CAPTIVE MOLECULES: THE STORY OF THE STEAM ENGINE
The development of the steam engine, p. 79--The manner in which
energy is generated by steam, p. 80--Action of cylinder and piston,
p. 81--Early attempts to utilize steam, p. 82--Beginnings of modern
discovery, p. 83--The "engine" of the Marquis of Worcester, p.
84--Thomas Savery's steam pump, p. 85--Denis Papin invents the piston
engine, p. 88--Newcomen's improved engine, p. 89--The use of these
engines in collieries, p. 90--The wastefulness of such engines, p.
92--The coming of James Watt, p. 93--Early experiments of Watt, p.
95--The final success of Watt's experiments, p. 97--Some of his early
engines, p. 98--Rotary motion, p. 99--Watt's engine, "Old Bess,"
p. 101--Final improvements and missed opportunities, p. 102--The
personality of James Watt, p. 107.
CHAPTER VI
THE MASTER WORKER
Improvements on Watt's engines, p. 110--Engines dispensing with the
walking beam, p. 111--The development of high-pressure engines, p.
112--Advantages of the high-pressure engine, p. 114--How steam acts
in the high-pressure engine, p. 116--Compound engines, p. 117--Rotary
engines, p. 119--Turbine engines, p. 124--The _Turbinia_ and other
turbine boats, p. 125--The action of steam in the turbine engine, p.
126--Advantages of the turbine engine, p. 127.
CHAPTER VII
GAS AND OIL ENGINES
Some early gas engines, p. 133--Dr. Stirling's hot-air engine, p.
133--Ericsson's hot-air engines, p. 134--The first practical gas
engine, p. 135--The Otto gas engine, p. 136--Otto's improvement by
means of compressed gas, p. 138--The "Otto cycle," p. 139--Adaptation
of gas engines to automobiles, p. 140--Rapid increase in the use
of gas engines, p. 141--Defects of the older hot-air engines, p.
145--Recent improvements and possibilities in the use of hot-air
engines, p. 146.
CHAPTER VIII
THE SMALLEST WORKERS
The relative size of atoms and electrons, p. 148--What is
electricity? p. 149--Franklin's one-fluid theory, p. 150--Modern
views, p. 153--Cathode rays and the X-ray, p. 156--How electricity
is developed, p. 159--The work of the dynamical current, p.
162--Theories of electrical action, p. 165--Practical uses of
electricity, p. 168.
CHAPTER IX
MAN'S NEWEST CO-LABORER: THE DYNAMO
The mechanism of the dynamo, p. 173--The origin of the dynamo, p.
176--The work of Ampère, Henry, and Faraday, p. 177--Perfecting the
dynamo, p. 178--A mysterious mechanism, p. 180--Curious relation
between magnetism and electricity as exemplified in the dynamo, p.
182.
CHAPTER X
NIAGARA IN HARNESS
The volume of water at the falls, p. 184--The point at which
the falls are "harnessed," p. 185--Within the power-house, p.
186--Penstocks and turbines, p. 188--A miraculous transformation
of energy, p. 189--Subterranean tail-races, p. 191--The effect on
the falls, p. 192--The transmission of power, p. 194--"Step-up" and
"step-down" transformers, p. 198.
CHAPTER XI
THE BANISHMENT OF NIGHT
Primitive torch and open lamp, p. 202--Tallow candle and perfected
lamp, p. 205--Gas lighting, p. 207--The incandescent gas mantle, p.
208--Early gas mantles, p. 209--How the incandescent gas mantle is
made, p. 211--The introduction of acetylene gas, p. 212--Chemistry
of acetylene gas, p. 214--Practical gas-making, p. 215--The triumph
of electricity, p. 218--Davy and the first electric light, p.
220--Helpful discoveries in electricity, p. 222--The Jablochkoff
candle, p. 223--Defects of the Jablochkoff candle, p. 225--The
improved arc light, p. 226--Edison and the incandescent lamp, p.
228--Difficulties encountered in finding the proper material for
a practical filament, p. 230--"Parchmentized thread" filament, p.
233--The tungsten lamp, p. 234--The mercury-vapor light of Peter
Cooper Hewitt, p. 236--Advantages and peculiarities of this light, p.
240.
CHAPTER XII
THE MINERAL DEPTHS
Early mining methods, p. 242--Prospecting and locating mines, p.
243--"Booming," p. 246--Conditions to be considered in mining,
p. 248--Dangerous gases in mines, p. 249--Artificial lights and
lighting, p. 251--Ventilation and drainage, p. 252--Electric
machinery in mining, p. 253--Electric drills, p. 254--Traction in
mining, p. 256--Various types of electric motors, p. 257--"Telphers,"
p. 261--Electric mining pumps, p. 263--Some remarkable demonstrations
of durability of electric pumps, p. 265--Electricity in coal mining,
p. 266--Electric lighting in mines, p. 269.
CHAPTER XIII
THE AGE OF STEEL
Rapid growth of the iron industry in recent years, p. 271--The Lake
Superior mines, p. 272--Methods of mining, p. 273--"Open-pit" mining,
p. 274--Mining with the steam shovel, p. 276--From mine to furnace,
p. 278--Methods of transportation, p. 279--Vessels of special
construction, p. 281--The conversion of iron ore into iron and steel,
p. 283--Blast furnaces, p. 284--Poisonous gases and their effect
upon the workmen, p. 286--From pig iron to steel, p. 287--Modern
methods of producing pig iron, p. 288--The Bessemer converter, p.
289--Sir Henry Bessemer, p. 291--The "Bessemer-Mushet" process, p.
293--Open-hearth method, p. 294--Alloy steels, p. 295.
CHAPTER XIV
SOME RECENT TRIUMPHS OF APPLIED SCIENCE
The province of electro-chemistry, p. 298--Linking the laboratory
with the workshop, p. 299--Soda manufactories at Niagara Falls, p.
300--Producing aluminum by the electrolytic process, p. 300--Old and
new methods compared, p. 301--Nitrogen from the air, p. 303--What
this discovery means to the food industries of the world, p.
304--Prof. Birkeland's method, p. 307--Another method of nitrogen
fixation, p. 309--Cost of production, p. 312--Electrical energy,
p. 313--Production of high temperatures with the electric arc, p.
314--The production of artificial diamonds by the explosion of
cordite, p. 315--Industrial problems of to-day and to-morrow, p. 316.
ILLUSTRATIONS
A PRIMITIVE USE OF THE ANIMAL MACHINE THAT IS
STILL IN VOGUE IN MANY EUROPEAN COUNTRIES _Frontispiece_
HORSE AND CATTLE POWER _Facing p._ 32
CRANES AND DERRICKS " 38
A BELGIAN MILK-WAGON " 56
TWO APPARATUSES FOR THE UTILIZATION OF ANIMAL
POWER " 60
WINDMILLS OF ANCIENT AND MODERN TYPES " 68
WATER WHEELS " 72
HYDRAULIC PRESS AND HYDRAULIC CAPSTAN " 76
THOMAS SAVERY'S STEAM ENGINE " 86
DIAGRAMS OF EARLY ATTEMPTS TO UTILIZE THE POWER
OF STEAM " 88
A MODEL OF THE NEWCOMEN ENGINE " 92
WATT'S EARLIEST TYPE OF PUMPING-ENGINE " 96
WATT'S ROTATIVE ENGINE " 100
JAMES WATT " 108
OLD IDEAS AND NEW APPLIED TO BOILER CONSTRUCTION " 114
COMPOUND ENGINES " 118
ROTARY ENGINES " 122
THE ORIGINAL PARSONS' TURBINE ENGINE AND THE RECORD-BREAKING
SHIP FOR WHICH IT IS RESPONSIBLE " 128
GAS AND OIL ENGINES " 136
AN ELECTRIC TRAIN AND THE DYNAMO THAT PROPELS IT " 174
WILDE'S SEPARATELY EXCITED DYNAMO " 178
THE EVOLUTION OF THE DYNAMO " 180
VIEW IN ONE OF THE POWER HOUSES AT NIAGARA " 186
ELECTRICAL TRANSFORMERS " 198
THOMAS A. EDISON AND THE DYNAMO THAT GENERATED
THE FIRST COMMERCIAL INCANDESCENT LIGHT " 228
A FLINT-AND-STEEL OUTFIT, AND A MINER'S STEEL MILL " 248
THE LOCOMOTIVE "PUFFING BILLY" AND A MODERN
COLLIERY TROLLEY " 258
THE CONQUEST OF NATURE
In the earlier volumes we have been concerned with the growth of
knowledge. For the most part the scientific delvers whose efforts have
held our attention have been tacitly unmindful, or even explicitly
contemptuous, of the influence upon practical life of the phenomena to
the investigation of which they have devoted their lives. They were and
are obviously seekers of truth for the mere love of truth.
But the phenomena of nature are not dissociated in fact, however
much we may attempt to localize and classify them. And so it chances
that even the most visionary devotee of abstract science is forever
being carried into fields of investigation trenching closely upon the
practicalities of every-day life. A Black investigating the laws of
heat is preparing the way explicitly, however unconsciously, for a Watt
with his perfected mechanism of the steam engine.
Similarly a Davy working at the Royal Institution with his newly
invented batteries, and intent on the discovery of new elements and the
elucidation of new principles, is the direct forerunner of Jablochkoff,
Brush, and Edison with their commercial revolution in the production of
artificial light.
Again Oersted and Faraday, earnestly seeking out the fundamental facts
as to the relations of electricity and magnetism, invent mechanisms
which, though they seem but laboratory toys, are the direct forerunners
of the modern dynamos that take so large a share in the world's work.
In a word, all along the line there is the closest association
between what are commonly called the theoretical sciences and what
with only partial propriety are termed the applied sciences. The
linkage of one with the other must never be forgotten by anyone who
would truly apprehend the status of those practical sciences which
have revolutionized the civilization of the nineteenth and twentieth
centuries in its most manifest aspects.
Nevertheless there is, to casual inspection, a somewhat radical
distinction between theoretical and practical aspects of science--just
as there are obvious differences between two sides of a shield.
And as the theoretical aspects of science have largely claimed our
attention hitherto, so its practical aspects will be explicitly
put forward in the pages that follow. In the present volume we are
concerned with those primitive applications of force through which
man early learned to add to his working efficiency, and with the
elaborate mechanisms--turbine wheels, steam engines, dynamos--through
which he has been enabled to multiply his powers until it is scarcely
exaggeration to say that he has made all Nature subservient to his
will. It is this view which justifies the title of the volume, which
might with equal propriety have been termed the Story of the World's
Work.
THE CONQUEST OF NATURE
I
MAN AND NATURE
"Young men," said a wise physician in addressing a class of graduates
in medicine, "you are about to enter the battle of life. Note that I
say the 'battle' of life. Not a playground, but a battlefield is before
you. It is a hard contest--a battle royal. Make no mistake as to that.
Your studies here have furnished your equipment; now you must go forth
each to fight for himself."
The same words might be said to every neophyte in whatever walk of
life. The pursuit of every trade, every profession is a battle--a
struggle for existence and for supremacy. Partly it is a battle against
fellow men; partly against the contending powers of Nature. The
physician meets rivalry from his brothers; but his chief battle is with
disease. In the creative and manufacturing fields which will chiefly
concern us in the following volumes, it is the powers of Nature that
furnish an ever-present antagonism.
No stone can be lifted above another, to make the crudest wall or
dwelling, but Nature--represented by her power of gravitation--strives
at once to pull it down again. No structure is completed before the
elements are at work defacing it, preparing its slow but certain ruin.
Summer heat and winter cold expand and contract materials of every
kind; rain and wind wear and warp and twist; the oxygen of the air
gnaws into stone and iron alike;--in a word, all the elements are at
work undoing what man has accomplished.
THE STRUGGLE FOR EXISTENCE
In the field of the agriculturist it is the same story. The earth which
brings forth its crop of unwholesome weeds so bountifully, resists
man's approaches when he strives to bring it under cultivation. Only by
the most careful attention can useful grains be made to grow where the
wildlings swarmed in profusion. Not only do wind and rain, blighting
heat and withering cold menace the crops; but weeds invade the fields,
the germs of fungoid pests lurk everywhere; and myriad insects attack
orchard and meadow and grain field in devastating legions.
Similarly the beasts which were so rugged and resistant while in
the wild state, become tender and susceptible to disease when made
useful by domestication. Aforetime they roamed at large, braving every
temperature and thriving in all weathers. But now they must be housed
and cared for so tenderly that they become, as Thoreau said, the
keepers of men, rather than kept by men, so much more independent are
they than their alleged owners. Tender of constitution, domesticated
beasts must be housed, to protect them from the blasts in which of yore
their forebears revelled; and man must slave day in and day out to
prepare food to meet the requirements of their pampered appetites.
He must struggle, too, to protect them from disease, and must care for
them in time of illness as sedulously as he cares for his own kith and
kin. Truly the ox is keeper of the man, and the seeming conquest that
man has wrought has cost him dear.
But of course the story has another side. After all, Nature is not so
malevolent as at first glance she seems. She has opposed man at every
stage of his attempted progress; yet at the same time she has supplied
him all his weapons for waging war upon her. Her great power of
gravitation opposes every effort he makes; yet without that same power
he could do nothing--he could not walk or stay upon the earth even; and
no structure that he builds would hold in place for an instant.
So, too, the wind that smites him and tears at his handiwork, may be
made to serve the purposes of turning his windmills and supplying him
with power.
The water will serve a like purpose in turning his mills; and, changed
to steam with the aid of Nature's store of coal, will make his steam
engines and dynamos possible. Even the lightning he will harness and
make subject to his will in the telegraphic currents and dynamos.
And in the fields, the grains which man struggles so arduously to
produce are after all no thing of his creating. They are only adopted
products of Nature, which he has striven to make serve his purpose by
growing them under artificial conditions. So, too, the domesticated
beasts are creatures that belong in the wilds and in distant lands. Man
has brought them, in defiance of Nature, to uncongenial climes, and
made them serve as workers and as food-suppliers where Nature alone
could not support them. Turn loose the cow and the horse to forage for
themselves here in the inhospitable north, and they would starve. They
survive because man helps them to combat the adverse conditions imposed
by Nature, yet no one of them could live for an hour were not the vital
capacities supplied by Nature still in control.
Everywhere, then, it is the opposing of Nature, up to certain limits,
with the aid of Nature's own tools, that constitutes man's work in the
world. Just in proportion as he bends the elements to meet his needs,
transforms the plants and animals, defies and exceeds the limitations
of primeval Nature--just in proportion as he conquers Nature, in a
word, is he civilized.
Barbaric man is called a child of Nature with full reason. He must
accept what Nature offers. But civilized man is the child grown to
adult stature, and able in a manner to control, to dominate--if you
please to conquer--the parent.
If we were to seek the means by which developing man has gradually
achieved this conquest, we should find it in the single word, Tools;
that is to say, machines for utilizing the powers of Nature, and, as
it were, multiplying them for man's benefit. So unique is the capacity
that man exerts in this direction, that he has been described as
"the tool-making animal." The description is absolutely accurate; it
is inclusive and exclusive. No non-human animal makes any form of
implement to aid it in performing its daily work; and contrariwise
every human tribe, however low its stage of savagery, makes use of more
or less crude forms of implements. There must have been a time, to be
sure, when there existed a man so low in intelligence that he had not
put into execution the idea of making even the simplest tool. But the
period when such a man existed so vastly antedates all records that it
need not here concern us. For the purpose of classifying all existing
men, and all the tribes of men of which history and pre-historic
archæology give us any record, the definition of man as the tool-making
animal is accurate and sufficient.
At first thought it might seem that an equally comprehensive definition
might describe man as the working animal. But a moment's consideration
shows the fallacy of such a suggestion. Man is, to be sure, the animal
that works effectively, thanks to the implements with which he has
learned to provide himself; but he shares with all animate creatures
the task of laboring for his daily necessities. This is indeed a
work-a-day world, and no creature can live in it without taking
its share in that perpetual conflict which bodily necessities make
imperative. Most lower animals confine their work to the mere securing
of food, and to the construction of rude habitations. Some, indeed,
go a step farther and lay up stores of food, in chance burrows or
hollow trees; a few even manufacture relatively artistic and highly
effective receptacles, as illustrated by the honeycomb made by the
bees and their allies. Again, certain animals, of which the birds
are the best representatives, construct temporary structures for the
purpose of rearing their young that attain a relatively high degree of
artistic perfection. The Baltimore oriole weaves a cloth of vegetable
fibre that is certainly a wonderful texture to be made with the aid of
claws and bill alone. It may be doubted whether human hands, unaided by
implements, could duplicate it. But it is crude enough compared with
even the coarsest cloth which barbaric races manufacture with the aid
of implements.
So it is with any comparison of animal work with the work of man, in
whatever field. The crudest human endeavor is superior to the best
non-human efforts; and the explanation is found always in the fact that
the ingenuity of man has enabled him to find artificial aids that add
to his power of manipulation. So large a share have these artificial
aids taken in man's evolution, that it has long been customary, in
studying the development of civilization, to make the use of various
types of implements a test of varying stages of human progress.
SCIENCE AND CIVILIZATION
The student of primitive life assures us, basing his statements on the
archæological records, that there was a time when the most advanced of
mankind had no tools made of better material than chipped stone. By
common consent that time is spoken of as the Rough Stone Age.
We are told that then in the course of immeasurable centuries man
learned to polish his stone implements, doubtless by rubbing them
against another stone, or perhaps with the aid of sand, thus producing
a new type of implement which has given its name to the Age of Smooth
or Polished Stone.
Then after other long centuries came a time when man had learned
to smelt the softer metals, and the new civilization which now
supplanted the old, and, thanks to the new implements, advanced upon it
immeasurably, is called the Age of Bronze.
At last man learned to accomplish the wonderful feat of smelting the
intractable metal, iron, and in so doing produced implements harder,
sharper, and cheaper than his implements of bronze; and when this
crowning feat had been accomplished, the Age of Iron was ushered in.
By common consent, students of the history of the evolution of society
accept these successive ages, each designated by the type of implements
with which the world's work was accomplished, as representing real and
definite stages of human progress, and as needing no better definition
than that supplied by the different types of implements.
Could the archæologist trace the stream of human progress still farther
back toward its source, he would find doubtless that there were several
great epochal inventions preceding the time of the Rough Stone Age,
each of which was in its way as definitive and as revolutionary in
its effects upon society, as these later inventions which we have just
named. To attempt to define them clearly is to enter the field of
uncertainty, but two or three conjectures may be hazarded that cannot
be very wide of the truth.
It is clear, for example, that if we go back in imagination to the very
remotest ancestors of man that can be called human, we must suppose a
vast and revolutionary stage of progress to have been ushered in by the
first race of men that learned to make habitual use of the simplest
implement, such as a mere club. When man had learned to wield a club
and to throw a stone, and to use a stone held in the hand to break the
shell of a nut, he had attained a stage of culture which augured great
things for the future. Out of the idea of wielded club and hurled stone
were to grow in time the ideas of hammer and axe and spear and arrow.
Then there came a time--no one dare guess how many thousands of years
later--when man learned to cover his body with the skin of an animal,
and thus to become in a measure freed from the thraldom of the weather.
He completed his enfranchisement by learning to avail himself of the
heat provided by an artificial fire. Equipped with these two marvelous
inventions he was able to extend the hitherto narrow bounds of his
dwelling-place, passing northward to the regions which at an earlier
stage of his development he dared not penetrate. Under stress of more
exhilarating climatic conditions, he developed new ideals and learned
to overcome new difficulties; developing both a material civilization
and the advanced mentality that is its counterpart, as he doubtless
never would have done had he remained subject to the more pampering
conditions of the tropics.
The most important, perhaps, of the new things which he was taught
by the seemingly adverse conditions of an inhospitable climate, was
to provide for the needs of a wandering life and of varying seasons
by domesticating animals that could afford him an ever-present food
supply. In so doing he ceased to be a mere fisher and hunter, and
became a herdsman. One other step, and he had conceived the idea of
providing for himself a supply of vegetable foods, to take the place
of that which nature had provided so bountifully in his old home in
the tropics. When this idea was put into execution man became an
agriculturist, and had entered upon the high road to civilization.
All these stages of progress had been entered upon prior to the time of
which the oldest known remains of the cave-dweller give us knowledge.
It were idle to conjecture the precise sequence in which these earliest
steps toward civilization were taken, and even more idle to conjecture
the length of time which elapsed between one step and its successor.
But all questions of precise sequence aside, it is clear that here were
four or five great ages succeeding one to another, that marked the
onward and upward progress of our primeval ancestor before he achieved
the stage of development that enabled him to leave permanent records of
his existence. And--what is particularly significant from our present
standpoint--it is equally clear that each of the great ages thus
vaguely outlined was dependent upon an achievement or an invention
that facilitated the carrying out of that scheme of never-ending work
which from first to last has been man's portion. How to labor more
efficiently, more productively; how to produce more of the necessaries
and of the luxuries that man's physical and mental being demands,
with less expenditure of toil--that from first to last has been the
ever-insistent problem. And the answer has been found always through
the development of some new species of mechanism, some new labor-saving
device, some ingenious manipulation of the powers of Nature.
If, turning from the hypothetical period of our primitive ancestor,
we consider the sweep of secure and relatively recent history, we
shall find that precisely the same thing holds. If we contrast the
civilization of Old Egypt and Babylonia--the oldest civilizations of
which we have any secure record--with the civilization of to-day, we
shall find that the differences between the one and the other are such
as are due to new and improved methods of accomplishing the world's
work.
Indeed, if we view the subject carefully, it will become more and
more evident that the only real progress that the historic period has
to show is such as has grown directly from the development of new
mechanical inventions. The more we study the ancient civilizations
the more we shall be struck with their marvelous resemblance, as
regards mental life, to the civilization of to-day. In their moral
and spiritual ideals, the ancient Egyptians were as brothers to the
modern Europeans. In philosophy, in art, in literature, the Age of
Pericles established standards that still remain unexcelled. In all the
subtleties of thought, we feel that the Greeks had reached intellectual
bounds that we have not been able to extend.
But when, on the other hand, we consider the material civilization of
the two epochs, we find contrasts that are altogether startling. The
little world of the Greeks nestled about the Mediterranean, bounded
on every side at a distance of a few hundred leagues by a _terra
incognita_. The philosophers who had reached the confines of the
field of thought, had but the narrowest knowledge of the geography of
our globe. They traversed at best a few petty miles of its surface
on foot or in carts; and they navigated the Mediterranean Sea, or at
most coasted out a little way beyond the Pillars of Hercules in boats
chiefly propelled by oars. By dint of great industry they produced a
really astonishing number of books, but the production of each one was
a long and laborious task, and the aggregate number indited during
the Age of Pericles in all the world was perhaps not greater than an
afternoon's output of a modern printing press.
In a word, these men of the classical period of antiquity, great as
were their mental, artistic, and moral achievements, were as children
in those matters of practical mechanics upon which the outward
evidences of civilization depend. Should we find a race of people
to-day in some hitherto unexplored portion of the earth--did such
unexplored portions still exist--living a life comparable to that
of the Age of Pericles, we should marvel no doubt at their artistic
achievements, while at the same time regarding them as scarcely better
than barbarians. Indeed this is more than unsupported hypothesis;
for has it not been difficult for the Western world to admit the
truly civilized condition of the Chinese, simply because that highly
intellectual race of Orientals has not kept abreast of the Occidental
changes in applied mechanics? Say what we will, this is the standard
which we of the Western world apply as the test of civilization.
If, sweeping over in retrospect the history of the world since the time
when the Egyptian and Babylonian civilizations were at their height,
we attempt some such classification of the stages of progress as that
which we a moment ago applied to pre-historic times, we shall be led to
some rather startling conclusions. In the broadest view, it will appear
that the age which ushered in the historic period continued unbroken
by the advance of any great revolutionary invention throughout the
long centuries of pre-Christian antiquity, and well into the so-called
Middle Ages of our newer era. Then came the invention of gunpowder, or
at least its introduction to the Western world--since the Chinaman here
lays claim to vague centuries of precedence. Following hard upon the
introduction of gunpowder, with its capacity to add to the destructive
efficiency of man's most sinister form of labor, came a mechanism no
less epoch-making in a far different field--the printing press.
But even these inventions, great as was their influence upon the
progress of civilization, can scarcely be considered, it seems to me,
as taking rank with the great epochal discoveries that gave their
names to the preceding ages. Nor can any invention of the sixteenth
or seventeenth century be hailed as really ushering in a new era. The
invention for which that honor was reserved was a development of the
eighteenth century; and did not come fully to its heritage until the
early days of the nineteenth century. The invention was the application
of steam to the purposes of mechanics. When this application was made,
as wide a gap was crossed as that which separated the Stone Age from
the Age of Metal; then the epoch in which the world was living when
history begins was brought to a close, and a new era, the Age of Steam,
was ushered in.
Scarcely had the world begun to adjust itself to the new conditions of
the Age of Steam, when yet another power was made subservient to man's
needs, and the Age of Steam was supplemented, not to say supplanted, by
the Age of Electricity. Of course the new progressive movements did not
necessarily imply elimination of old conditions; they imply merely the
subordination of old powers to newer and better ones. Stone implements
by no means ceased to have utility at once when metal implements came
into vogue. Bronze long held its own against iron, and still has its
utility. And iron itself finds but an added sphere of usefulness in the
Age of Steam and Electricity.
All great changes are relatively slow. It is only as we look back upon
them and view them in perspective that they seem cataclysmic. Gunpowder
did not at once supplant the crossbow, and the cannon was long held
to be inferior to the catapult. The printed book did not instantly
make its way against the work of the scribe. Neither did the steam
engine immediately supplant water power and the direct application of
human labor. But in each case the new invention virtually rang the
death knell of the old method from the hour of its inauguration, and
the end was no less sure because it was delayed. And it requires no
great powers of divination to foretell that in the coming age, the
electric dynamo driven by water power may take the place of the steam
engine. The Age of Steam may pass, with only at most a few generations
of domination. And it is within the possibilities that the Age of
Electricity will scarcely come into its own before it may be displaced
by an Age of Radio-Activity. To press that point, however, would be to
enter the field of prophecy, which is no part of my present purpose.
All that I have wished to point out is that for some thousands of
years after man learned to make implements of iron, the industrial
world and the human civilization that depends upon it, pursued a
relatively static course, like a broad, sluggish current, with no
new revolutionary discovery to impel it into new channels; and that
then one revolutionary discovery succeeded another with bewildering
suddenness, so that we of the early days of the twentieth century
are farther removed, in an industrial way, from our forerunners of
two hundred years ago, than those children of the eighteenth century
were from the earliest civilization that ever developed on our globe.
Indeed, this startling contrast would still hold true, were we to
consider the newest era as compassing only the period of a single
life. There are men living to-day who were born in that epoch when
the steam engine was for the first time used to turn the wheels of
factories. There are many men who can well remember the first practical
application of steam to railway traffic. Hosts of men can remember when
the first commercial message was transmitted by electricity along a
wire. Even middle-aged men recall the first cable message that linked
the old world with the new. And the application of the dynamo to the
purposes of the world's work is an affair of but yesterday.
The historian of the future, casting his eye back across the long
perspective of history, will find civilized man pursuing an even and
unbroken course across the ages from the time of the pyramids of Egypt
to about the time of the French Revolution. There will be no dearth
of incident to claim his attention in the way of wars and conquests,
and changing creeds, and the rise and fall of nations, each pursuing
virtually the same course of growth and decay as all the others. But
when he comes to the close of the eighteenth century, it will not be
the social paroxysm of a nation, or the meteoric career of a Napoleon
that will claim his attention so much as the introduction of that new
method of utilizing the powers of Nature which found its expression in
the mechanism called the steam engine.
If the name of any individual stands out as the great and memorable one
of that epoch of transition, at which the static current of previous
civilization changed suddenly to a Niagara-current of progress, it will
be the name of the great scientific inventor, rather than that of the
great military conqueror--the name of James Watt, rather than that of
Napoleon.
The military conqueror had his day of surpassing glory and departed,
to leave the world only a little worse than he found it. But the
mechanical inventor left a heritage that was to add day by day to the
wealth and happiness of humanity, supplying millions of artificial
hands, and making possible such beneficent improvements as no previous
age had dreamed of. Tasks that human hands had performed slowly,
laboriously, and inadequately, were now to be performed swiftly, with
ease, and well by the artificial hands provided with the aid of the new
power. Where carts drawn by horses had toiled slowly across the land,
and ships driven by the wind had drifted slowly through the waters,
massive trains of cars were to hurtle to the four corners of the earth
with inconceivable speed, and floating palaces were to course the
waters with almost equal defiance to the limitations of time and space.
And then there came that still weirder conquest of time and space,
wrought by the electric current. The moment when man first spoke with
man from continent to continent in defiance of the oceans, marked
the dawning of that larger day when all mankind shall constitute one
brotherhood and all peoples but a single nation. Within a half century
the sun of that new day has risen well above the horizon, and far
sooner than even the optimist of to-day dare predict with certainty, it
seems destined to reach its zenith.
But here again we verge upon the dangerous field of prophecy. Let
us turn from it and cast an eye back across the most wonderful of
centuries, contrasting the conditions of to-day in each of a half-dozen
fields of the world's work, with the conditions that obtained at the
close of the eighteenth century. Such a brief survey will show us
perhaps more vividly than we could otherwise be shown, how vast has
been the progress, how marvelous the development of civilization, in
the short decades that have elapsed since the coming of the Age of
Steam.
Let us pay heed first to the world of the agriculturist. Could we
turn back to the days of our grandparents, we should find farming a
very different employment from what it is to-day. For the most part
the farmer operated but a few small fields; if he had thirty or forty
acres of ploughed land, he found ample employment for his capacities.
He ploughed his fields with the aid of either a yoke of oxen or a
team of horses; he sowed his grain by hand; he cultivated his corn
with a hoe; he reaped his oats and wheat with a cradle--a device but
one step removed from a sickle; he threshed his grain with a flail;
he ground such portion of it as he needed for his own use with the
aid of water power at a neighboring mill; and such portion of it as
he sold was transported to market, be it far or near, in wagons that
compassed twenty or thirty miles a day at best. As regards live stock,
each farmer raised a few cattle, sheep, and hogs, and butchered them
to supply his own needs, selling the residue to a local dealer who
supplied the non-agricultural portion of the neighborhood. Any live
stock intended for a distant market was driven on foot across the
country to its destination. Each town and city, therefore, drew almost
exclusively for its supply from the immediately surrounding country.
To-day the small farmer has become almost obsolete, and the farms
of the eastern states that were the nation's chief source of supply
a century ago are largely allowed to lie fallow, it being no longer
possible to cultivate them profitably in competition with the rich
farm lands of the middle west. In that new home of agriculture, the
farm that does not comprise two or three hundred acres is considered
small; and large farms are those that number their acres by thousands.
The soil is turned by steam ploughs; the grain is sown with mechanical
seeders and planters; the corn is cultivated with a horse-drawn
machine, having blades that do the work of a dozen men; harvesters
drawn by three or four horses sweep over the fields and leave the grain
mechanically tied in bundles; the steam thresher places the grain in
sacks by hundreds of bushels a day; and this grain is hurried off in
steam cars to distant mills and yet more distant markets.
Meantime the raising of live stock has become a special department,
with which the farmer who deals in cereals often has no concern.
The cattle roam over vast pastures and are herded in the winter for
fattening in great droves, and protected from the cold in barns
that, when contrasted with the sheds of the old-time farmer, seem
almost palatial. When in marketable condition, cattle are no longer
slaughtered at the farm, but are transported in cars to one of the
few great centres, chief of which are the stock yards of Chicago and
of Kansas City. At these centres, slaughter houses and meat-packing
houses of stupendous magnitude have been developed, capable of
handling millions of animals in a year. From these centres the meat is
transported in refrigerator cars to the seaboards, and in refrigerator
ships to all parts of the world. Beef that grew on the ranges of the
far west may thus be offered for sale in the markets of New England
villages, at a price that prohibits local competition.
A more radical metamorphosis in agricultural conditions than all this
implies could not well be conceived. And when we recall once more that
the agricultural conditions that obtained at the beginning of the
nineteenth century were closely similar to those that obtained in each
successive age for a hundred preceding centuries, we shall gain a vivid
idea of the revolutionizing effects of new methods of work in the most
important of industries. It is little wonder that in this short time
the world has not solved to the satisfaction of the economists all the
new problems thus so suddenly developed.
Turn now to the manufacturing world. In the days of our
great-grandparents almost every household was a miniature factory where
cotton and wool were spun and the products were woven into cloth.
It was not till toward the close of the eighteenth century--just at
the time when Watt was perfecting the steam engine--that Arkwright
developed the spinning-frame, and his successors elaborated the
machinery that made possible the manufacture of cloth in wholesale
quantities; and the nineteenth century was well under way before
the household production of cloth had been entirely supplanted by
factory production. It is nothing less than pitiful to contemplate in
imagination our great-great-grandmothers--and all their forebears of
the long centuries--drudging away day after day, year in and year out,
at the ceaseless task of spinning and weaving--only to produce, as the
output of a lifetime of labor, a quantity of cloth equivalent perhaps
to what our perfected machine, driven by steam, and manipulated by
a factory girl, produces each working hour of every day. Similarly,
carpets and quilts were of home manufacture; so were coats and dresses;
and shoes were at most the product of the local shoemaker around the
corner.
In the kitchen, food was cooked over the coals of a great fireplace
or in the brick oven connected with that fireplace. Meat was supplied
from a neighboring farm; eggs were the product of the housewife's own
poultry yard; the son or daughter of the farmer milked the cow and
drove her to and from the pasture; the milk was "set" in pans in the
cellar--on a swinging shelf, preferably, to make it inaccessible to the
rats; and twice a week the cream was made into butter in a primitive
churn, the dasher of which was operated by the vigorous arm of the
housewife herself, or by the unwilling arms of some one of her numerous
progeny.
To give variety to the dietary, fruits grown in the local garden
or orchard were preserved, each in its season, by the industrious
housewife, and stored away in the capacious cellar; where also might be
found the supply of home-grown potatoes, turnips, carrots, parsnips,
and cabbages to provide for the needs of the winter. Fuel to supply
the household needs, both for cooking and heating, was cut in the
neighboring woodland, and carefully corded in the door-yard, where it
provided most uncongenial employment for the youth of the family after
school hours and of a Saturday afternoon.
The ashes produced when this wood was burned in the various fireplaces,
were not wasted, but were carefully deposited in barrels, from which
in due course lye was extracted by the simple process of pouring water
over the contents of the barrel. Meantime scraps of fat from the table
were collected throughout the winter and preserved with equal care; and
in due course on some leisure day in the springtime--heaven knows how a
leisure day was ever found in such a scheme of domestic economy!--the
lye drawn from the ash-barrels and the scraps of fat were put into a
gigantic kettle, underneath which a fire was kindled; with the result
that ultimately a supply of soft soap was provided the housewife, with
which her entire establishment, progeny included, could be kept in a
state of relative cleanness.
The reader of these pages has but to cast his eye about him in the
household in which he lives, and contrast the conditions just depicted
with those of his every-day life, to realize what change has come over
the aspects of household economy in the course of a short century.
Nor need he be told in each of the various departments of which the
activities are here outlined, that the changes which he observes have
been due to the application of machinery in all the essential lines of
work in question. We need not pause to detail the multitudinous devices
for the economy of household labor which owe their origin to the same
agency. There still remains, to be sure, enough of drudgery in the task
of the housewife; yet her most strenuous day seems a mere playtime in
comparison with the average day of her maternal forebear of three or
four generations ago.
But we must not here pause for further outlines of a subject which it
is the purpose of this and succeeding volumes to explicate in detail.
All our succeeding chapters will but make it more clear how marvelous
are the elaborations of method and of mechanism through which the
world's work of to-day is accomplished. We shall consider first the
mechanical principles that underlie work in general, passing on to
some of the principal methods of application through which the powers
of Nature are made available. We shall then take up in succession
the different fields of industry. We shall ask how the work of the
agriculturist is done in the modern world; how the multitudinous lines
of manufacture are carried out; how transportation is effected; we
shall examine the _modus operandi_ of the transmission of ideas; we
shall even consider that destructive form of labor which manifests
itself in the production of mechanisms of warfare. As we follow out the
stories of the all-essential industries we shall be led to realize more
fully perhaps than we have done before, the meaning of work in its
relations to human development; and in particular the meaning of modern
work, as carried out with the aid of modern mechanical contrivances, in
its relations to modern civilization.
The full force of these relations may best be permitted to unfold
itself as the story proceeds. There is, however, one fundamental
principle which I would ask the reader to bear constantly in mind, as
an aid to the full appreciation of the importance of our subject. It
is that in considering the output of the worker we have constantly to
do with one form or another of property, and that property is the very
foundation-stone of civilization. "It is impossible," says Morgan,
in his work on Ancient Society, "to overestimate the influence of
property in the civilization of mankind. It was the power that brought
the Aryan and Semitic nations out of barbarism into civilization.
The growth of the idea of property in the human mind commenced in
feebleness and ended in becoming its master passion. Governments and
laws are instituted with primary reference to its creation, protection,
and enjoyment. It introduced human slavery in its production; and,
after the experience of several thousand years, it caused the
abolition of slavery upon the discovery that the freeman was a better
property-making machine." If, then, we recall that without labor there
is no property, we shall be in an attitude of mind to appreciate the
importance of our subject; we shall realize, somewhat beyond the bounds
of its more tangible and sordid relations, the essential dignity, the
fundamental importance--in a word, the true meaning--of Work.
Undoubtedly there is a modern tendency to accept this view of the
dignity of physical labor. At any rate, we differ from the savage in
thinking it more fitting that man should toil than that his wife should
labor to support him--though it cannot be denied that even now the
number of physical toilers among women greatly exceeds the number of
such toilers among men. But in whatever measure we admit this attitude
of mind, there can be no question that it is exclusively a modern
attitude. Time out of mind, physical labor has been distasteful to
mankind, and it is a later development of philosophy that appreciates
the beneficence of the task so little relished.
The barbarian forces his wife to do most of the work, and glories in
his own freedom. Early civilization kept conquered foes in thraldom,
developing an hereditary body of slaves, whose function it was to do
the physical work.
The Hebrew explained the necessity for labor as a curse imposed upon
Father Adam and Mother Eve. Plato and Aristotle, voicing the spirit of
the Greeks, considered manual toil as degrading.
To-day we hear much of the dignity of labor; but if we would avoid cant
we must admit that now--scarcely less than in all the olden days--the
physical toiler is such because he cannot help himself. Few indeed are
the manual laborers who know any other means of getting their daily
bread than that which they employ. The most strenuous advocates of the
strenuous life are not themselves tillers of the soil or workers in
factories or machine shops.
The farm youth of intelligence does not remain a farmer; he goes to
the city, and we find him presently at the head of a railroad or a
bank, or practising law or medicine. The more intelligent laborer
becomes finally a foreman, and no longer handles the axe or sledge. We
should think it grotesque were we to see a man of intellectual power
obstinately following a pursuit that cost him habitual physical toil.
When now and then a Tolstoi offers an exception to this rule, we feel
that he is at least eccentric; and we may be excused the doubt whether
he would follow the manual task cheerfully if he did not know that he
could at any moment abandon it. It is because he knows that the world
understands him to be only a dilettante that he rejoices in his task.
After all, then, judged by the modern practice, rather than by the
philosopher's precept, the old Hebrew and Greek ideas were not so
far wrong. Using the poetical language which was so native to them,
it might be said that the necessity for physical labor is a curse--a
disgrace.
A partial explanation of this may be found in the fact that the most
uncongenial tasks are also the worst paid, while the congenial tasks
command the high emoluments. Generally speaking there is no distinction
between one laborer and another in the same field--except where the
eminently fair method of piece work can be employed. Even the skilled
laborer is usually paid by the day, and the amount he is to receive is
commonly fixed by a Union regardless of his efficiency as compared with
other laborers of the same class. And there is no possibility of his
receiving any such sums as the man who plans the work, but does nothing
with his own hands.
It has always been so. Just as "those who think must govern those that
toil," so the thinker must command the high reward. Partly this is
because man, considered as a mere toiler, is so relatively inefficient
a worker. When he strives to work with his hands, his effort is but a
pitiful one; he can by no possibility compete (as regards mere quantity
of labor) with the ox and the horse. He is impatient of his own puerile
efforts. It is only when he brings the products of ingenuity to his
aid that he is able to show his superiority, and to justify his own
egotism. So it is that in every age he has striven to find means of
adding to his feeble powers of body through the use of his relatively
gigantic powers of mind. And in proportion as he thus is able to "make
his head work for his hands" as the saying goes, he verges toward the
heights of civilization. To accomplish this more and more fully has
ever been the task of science as applied to the industries.
It will be our object in the ensuing chapters to inquire how far
science has accomplished the protean task thus set for it. We shall see
that much has been done; but that much still remains to be done. In
proportion as the problems are unsolved, science is reproached for its
shortcomings--and stimulated to new efforts.
In proportion as labor has been minimized and production increased--in
just that proportion has science justified itself; and in the same
proportion has the Conquest of Nature been carried toward completion.
II
HOW WORK IS DONE
The word energy implies capacity to do work. Work, considered in
the abstract, consists in the moving of particles of matter against
some opposing force, or in aid of previously acting forces. In the
last analysis, all energy manifests itself either as a push or as a
pull. But there is a modification of push and pull which is familiar
to everyone in practice under the name of prying. Illustrations may
be seen on every hand, as when a workman pries up a stone, or when
a housewife pries up a tack with the aid of a hammer. The principle
here involved is that of the lever--a principle which in its various
practical modifications is everywhere utilized in mechanics. Very
seldom indeed is the direct push or pull utilized; since the modified
push or pull, as represented by the lever in its various modifications
of pulley, ratchet-wheel, and the like, has long been known to meet the
needs of practical mechanics.
The very earliest primitive man who came to use any implement whatever,
though it were only a broken stick, must have discovered the essential
principle of the lever, though it is hardly necessary to add that he
did not know his discovery by any such high-sounding title. What he
did know, from practical experience, was that with the aid of a stick
he could pry up stones or logs that were much too heavy to be lifted
without this aid.
This practical knowledge no doubt sufficed for a vast number of
generations of men who used the lever habitually, without making
specific study of the relations between the force expended, the lengths
of the two ends of the lever, and the weight raised. Such specific
experiments were made, however, more than two thousand years ago by the
famous Syracusan, Archimedes. He discovered--or if some one else had
discovered it before him, he at least recorded and so gains the credit
of discovery--the specific laws of the lever, and he also pointed out
that levers, all acting on the same principle, may be different as to
their practical mechanism in three ways.
First, the fulcrum may lie between the power and the weight, as in the
case of the balance with which we were just experimenting. This is
called a lever of the first class, and familiar illustrations of it are
furnished by the poker, steelyard, or a pair of scissors. The so-called
extensor muscles of the body--those for example, that cause the arm to
extend--act on the bones in such a way as to make them levers of this
first class.
The second type of lever is that in which the weight lies between the
force and the fulcrum, as illustrated by the wheelbarrow, or by an
ordinary door.
In the third class of levers the power is applied between weight and
fulcrum, as illustrated by a pair of tongs, the treadle of a lathe,
or by the flexor muscles of the arm, operating upon the bones of the
forearm.
But in each case, let it be repeated, precisely the same principles are
involved, and the same simple law of the relations between positions
of power, weight, and fulcrum are maintained. The practical result
is always that a weight of indefinite size may be moved by a power
indefinitely long. If one arm of the lever is ten times as long as the
other, the power of one pound will lift or balance a ten-pound weight;
if the one arm is a thousand times as long as the other the power of
one pound will lift or balance a thousand pounds. If the long arm of
the lever could be made some millions of miles in length, the power
that a man could exert would balance the earth.
How fully Archimedes realized the possibilities of the lever is
illustrated in the classical remark attributed to him, that, had he
but a fulcrum on which to place his lever, he could move the world. As
otherwise quoted, the remark of Archimedes was that, had he a place
on which to stand, he could move the world, a remark which even more
than the other illustrates the full and acute appreciation of the
laws of motion; since, as we have already pointed out, action and
reaction being equal, the most infinitesimal push must be considered as
disturbing even the largest body.
Tremendous as is the pull of gravity by which the earth is held in
its orbit, yet the smallest push, steadily applied from the direction
of the sun, would suffice ultimately to disturb the stability of our
earth's motion, and to push it gradually through a spiral course
farther and farther away from its present line of elliptical flight.
Or if, on the other hand, the persistent force were applied from the
side opposite the sun, it would suffice ultimately to carry the earth
in a spiral course until it plunged into the sun itself. Indeed it has
been questioned in modern times whether it may not be possible that
precisely this latter effect is gradually being accomplished, through
the action of meteorites, some millions of which fall out of space into
the earth's atmosphere every day. If these meteorites were uniformly
distributed through space and flying in every direction, the fact that
the sun screens the earth from a certain number of them, would make
the average number falling on the side away from the sun greater, and
thus would in the course of ages produce the result just suggested. All
that could save our earth from such a fate would be the operation of
some counteracting force. Such a counteracting force is perhaps found
in solar radiation. It may be added that the distribution of meteorites
in space is probably too irregular to make their influence on the earth
predicable in the present state of science; but the principle involved
is no less sure.
WHEELS AND PULLEYS
Returning from such theoretical applications of the principle of
motion, to the practicalities of every-day mechanisms, we must note
some of the applications through which the principle of the lever is
made available. Of these some of the most familiar are wheels, and the
various modifications of wheels utilized in pulleys and in cogged
and bevelled gearings. A moment's reflection will make it clear that
the wheel is a lever of the first class, of which the axle constitutes
the fulcrum. The spokes of the wheel being of equal length, weights
and forces applied to opposite ends of any diameter are, of course,
in equilibrium. It follows that when a wheel is adjusted so that a
rope may be run about it, constituting a simple pulley, a mechanism is
developed which gives no gain in power, but only enables the operator
to change the direction of application of power. In other words, pound
weights at either end of a rope passed about a simple pulley are
in equilibrium and will balance each other, and move through equal
distances in opposite directions.
[Illustration: HORSE AND CATTLE POWER.
The large picture shows a model of a familiar mechanism for utilizing
horse power. The small picture shows a similar apparatus in actual
operation, actuated by cattle, in contemporary Brittany.]
If, however, two or more pulley wheels are connected, to make the
familiar apparatus of a compound pulley, we have accomplished by an
interesting mechanism a virtual application of the principle of the
long and short arm of the lever, and the relations between the weight
at the loose end of the rope and the weight attached to the block
which constitutes virtually the short end of the lever, may be varied
indefinitely, according to the number of pulley-wheels that are used.
A pound weight may be made to balance a thousand-pound weight; but,
of course, our familiar principle still holding, the pound weight
must move through a distance of a thousand feet in order to move
a thousand-pound weight through a distance of one foot. Familiar
illustrations of the application of this principle may be seen on every
hand; as when, for example, a piano or a safe is raised to the upper
window of a building by the efforts of men whose power, if directly
expended, would be altogether inefficient to stir the weight.
The pulley was doubtless invented at a much later stage of human
progress than the simple lever. It was, however, well known to the
ancients. It was probably brought to its highest state of practical
perfection by Archimedes, whose experiments are famous through the
narrative of Plutarch. It will be recalled that Archimedes amazed
the Syracusan general by constructing an apparatus that enabled
him, sitting on shore, to drag a ponderous galley from the water.
Plutarch does not describe in detail the apparatus with which this
was accomplished, but it is obvious from his description of what took
place, that it must have been a system of pulleys.
It will be observed that the pulley is a mechanism that enables the
user to transmit power to a distance. But this indeed is true in a
certain sense of every form of lever. Numberless other contrivances
are in use by which power is transmitted, through utilization of the
same principle of the lever, either through a short or through a
relatively long distance. A familiar illustration is the windlass,
which consists of a cylinder rotating on an axis propelled by a long
handle, a rope being wound about the cylinder. This is a lever of
the second class, the axis acting as fulcrum, and the rope operating
about the circumference of the cylinder typifying the weight, which
may be actually at a considerable distance, as in the case of the
old-fashioned well with its windlass and bucket, or of the simple form
of derrick sometimes called a sheerlegs.
OTHER MEANS OF TRANSMITTING POWER
Power is transmitted directly from one part of a machine to another,
in the case of a great variety of machines, with the aid of cogged
gearing wheels of various sizes. The modifications of detail in the
application of these wheels may be almost infinite, but the principle
involved is always the same. The case of two wheels toothed about
the circumference, the teeth of the two wheels fitting into one
another, illustrates the principle involved. A consideration of the
mechanism will show that here we have virtually a lever fixed at both
ends, represented by the radii of the two wheels, the power being
applied through the axle of one wheel, and the weight, for purposes
of calculation, being represented by the pressure of the teeth of one
wheel upon those of the other. So this becomes a lever of the second
class, and the relations of power between the two wheels are easily
calculated from the relative lengths of the radii. If, for example,
one radius is twice as long as the other, the transmission of power
will be, obviously, in the proportion of two to one, and meantime the
distance traversed by the circumference of one wheel will be twice as
great as that traversed by the other.
A modification of the toothed wheel is furnished by wheels which may be
separated by a considerable distance, and the circumferences of which
are connected by a belt or by a chain. The principle of action here
is precisely the same, the belt or chain serving merely as a means of
lengthening out our lever. The relative sizes of the wheels, and not
the length of the belt or chain, is the determining factor as regards
the relative forces required to make the wheels revolve.
It is obvious all along, of course, since action and reaction
are equal, that all of the relations in question are reciprocal.
When, for example, we speak of a pound weight on the long end of a
lever balancing a ten-pound weight on the short end, it is equally
appropriate to speak of the ten-pound weight as balancing the one-pound
weight. Similarly, when power is applied to the lever, it may be
applied at either end. Ordinarily, to be sure, the power is applied
at the long end, since the object is to lift the heavy weight; but in
complicated machinery it quite as often happens that these conditions
are reversed, and then it becomes desirable to apply strong power to
the short end of the lever, in order that the relatively small weight
may be carried through the long distance. In the inter-relations of
gearing wheels, such conditions very frequently obtain, practical ends
being met by a series of wheels of different sizes. But the single
rule, already so often outlined, everywhere holds--wherever there is
gain of power there is loss of distance, and we can gain distance only
by losing power. The words gain and loss in this application are in a
sense misnomers, since, as we have already seen, gain and loss are only
apparent, but their convenience of application is obvious.
A familiar case in which there is first loss of speed and gain of
power, and then gain of speed at the expense of power in the same
mechanism, is furnished by the bicycle, where (1) the crank shaft
turns the sprocket wheel that constitutes a lever of the second class
with gain of power; where (2) power is further augmented through
transmission from the relatively large sprocket wheel to the small
sprocket of the axle; and where (3) there is great loss of power and
corresponding gain of speed in transmitting the force from the small
sprocket wheel at the axle to the rubber rim of the bicycle proper,
this last transmission representing a lever of the third class. The net
gain of speed is tangibly represented by the difference in distance
traversed by the man's feet in revolving the pedals, and the actual
distance covered by the bicycle.
INCLINED PLANES AND DERRICKS
A less obvious application of the principle of reciprocal equivalence
of distance and weight is furnished by the inclined plane, a familiar
mechanism with the aid of which a great gain of power is possible. The
inclined plane, like the lever, has been known from remotest antiquity.
Its utility was probably discovered by almost the earliest builders.
Diodorus Siculus tells us that the great pyramids of Egypt were
constructed with the aid of inclined planes, based on a foundation of
earth piled about the pyramids. Diodorus, living at a period removed by
some thousands of years from the day of the building of the pyramids,
may or may not have voiced and recorded an authentic tradition, but we
may well believe that the principle of the inclined plane was largely
drawn upon by the mechanics of old Egypt, as by later peoples.
The law of the inclined plane is that in order to establish equilibrium
between two weights, the one must be to the other as the height of
the inclined plane is to its length. The steeper the inclined plane,
therefore, the less will be the gain in power; a mechanical principle
which familiar experience or the simplest experiment will readily
corroborate.
In its elemental form the inclined plane is not used very largely in
modern machinery, but its modified form of the wedge and the screw have
more utility. The screw, indeed, which is obviously an inclined plane
adjusted spirally about a cylinder or a cone, is familiar to everyone,
and is constantly utilized in applying power.
The crane or derrick furnishes a familiar but relatively elaborate
illustration of a mechanism for the transmission of power, in which
all the various devices hitherto referred to are combined, without the
introduction of any new principle.
Derricks have been employed from a very early day. The battering-rams
of the ancient Egyptians and Babylonians, for example, were virtually
derricks; and no doubt the same people used the device in raising
stones to build their temples and city walls, and in putting into
position such massive sculptures as the obelisks of Egypt and the
monster graven bulls and lions of Nineveh and Babylon.
[Illustration: CRANES AND DERRICKS.
The upper figure shows a floating derrick, the lower right-hand figure
a combined derrick and weighing machine, and the lower left-hand figure
a so-called sheerlegs, which is a simple derrick and windlass operated
by hand or by steam power with the aid of compound pulleys.]
The modern derrick, made of steel, and operated by steam or
electricity, capable of lifting tons, yet absolutely obedient to the
hand of the engineer, is a really wonderful piece of mechanism. A
steam-scoop, for example, excavating a gravel bank, seems almost
a thing of intelligence; as it gores into the bank scooping up
perhaps a half ton of earth, its upward sweeping head reminds one of
an angry bull. Then as it swings leisurely about and discharges its
load at just the right spot into an awaiting car, its hinged bottom
swings back and forth two or three times before closing, with curious
resemblance to the jaw of a dog; the similarity being heightened
by the square bull-dog-headed shape of the scoop itself. Yet this
remarkable contrivance, with all its massive steel beams and chains
and cog wheels, employs no other principles than the simple ones of
lever and pulley and inclined plane that we have just examined. The
power that must be applied to produce a given effect may be calculated
to a nicety. The capacities of the machine are fully predetermined
in advance of its actual construction. But of course this is equally
true of every other form of power-transmitter with which the modern
mechanical engineer has to deal.
FRICTION
In making such calculations, however, there is an additional element
which the engineer must consider, but which we have hitherto
disregarded. In all methods of transmission of power, and indeed in all
cases of the contact of one substance with another, there is an element
of loss through friction. This is due to the fact that no substance
is smooth except in a relative sense. Even the most highly polished
glass or steel, when viewed under the microscope, presents a surface
covered with indentations and rugosities. This granular surface of
even seemingly smooth objects, is easily visualized through the analogy
of numberless substances that are visibly rough. Yet the vast practical
importance of this roughness is seldom considered by the casual
observer. In point of fact, were it not for the roughened surface of
all materials with which we come in contact, it would be impossible for
any animal or man to walk, nor could we hold anything in our hands.
Anyone who has attempted to handle a fish, particularly an eel, fresh
from the water, will recall the difficulty with which its slippery
surface was held; but it may not occur to everyone who has had this
experience that all other objects would similarly slip from the hand,
had their surfaces a similar smoothness. The slippery character of the
eel is, of course, due in large part to the relatively smooth surface
of its skin, but partly also to the lubricant with which it is covered.
Any substance may be rendered somewhat smoother by proper lubrication;
it is necessary, however, that the lubricant should be something
which is not absorbed by the substance. Thus, wood is given increased
friction by being moistened with oil, but, on the other hand, is made
slippery if covered with graphite, soap, or any other fatty substances
that it does not absorb.
Recalling the more or less roughened surface of all objects, the source
of friction is readily understood. It depends upon the actual jutting
of the roughened surfaces, one upon the other. It virtually constitutes
a force acting in opposition to the motion of any two surfaces
upon each other. As between any different materials, under given
conditions, it varies with the pressure, in a definite and measurable
rate, which is spoken of as the coefficient of friction for the
particular substances. It is very much greater where the two substances
slide over one another than where the one rolls upon the other, as in
the case of the wheel. The latter illustrates what is called rolling
friction, and in practical mechanics it is used constantly to decrease
the loss--as, for example, in the wheels of wagons and cars. The use of
lubricants to decrease friction is equally familiar. Without them, as
everyone knows, it would be impossible to run any wheel continuously
upon an axle at high speed for more than a very brief period, owing
to the great heat developed through friction. Friction is indeed a
perpetual antagonist of the mechanician, and we shall see endless
illustrations of the methods he employs to minimize its influence. On
the other hand, we must recall that were it rendered absolutely _nil_,
his machinery would all be useless. The car wheel, for example, would
revolve indefinitely without stirring the train, were there absolutely
no friction between it and the rail.
AVAILABLE SOURCES OF ENERGY
We have pointed out that every body whatever contains a certain store
of energy, but it has equally been called to our attention that, in
the main, these stores of energy are not available for practical use.
There are, however, various great natural repositories of energy upon
which man is able to draw. The chief of these are, first, the muscular
energy of man himself and of animals; second, the energy of air in
motion; third, the energy of water in motion or at an elevation; and
fourth, the molecular and atomic energies stored in coal, wood, and
other combustible materials. To these we should probably add the energy
of radio-active substances--a form of energy only recently discovered
and not as yet available on a large scale, but which may sometime
become so, when new supplies of radio-active materials have been
discovered. It will be the object of succeeding chapters to point out
the practical ways in which these various stores of energy are drawn
upon and made to do work for man's benefit.
III
THE ANIMAL MACHINE
The muscular system is not only the oldest machine in existence,
but also the most complex. Moreover, it is otherwise entitled to
precedence, for even to-day, in this so-called age of steam and
electricity, the muscular system remains by far the most important of
all machines. In the United States alone there are some twenty million
horses doing work for man; and of course no machine of any sort is
ever put in motion or continues indefinitely in operation without
aid supplied by human muscles. All in all, then, it is impossible to
overestimate the importance of this muscular machine which is at once
the oldest and the most lasting of all systems of utilizing energy.
The physical laws that govern the animal machine are precisely similar
to those that are applied to other mechanisms. All the laws that have
been called to our attention must therefore be understood as applying
fully to the muscular mechanism. But in addition to these the muscular
system has certain laws or methods of action of its own, some of which
are not very clearly understood.
The prime mystery concerning the muscle is its wonderful property of
contracting. For practical purposes we may say that it has no other
property; the sole function of the muscle is to contract. It can, of
course, relax, also, to make ready for another contraction, but this
is the full extent of its activities. A microscopic examination of
the muscle shows that it is composed of minute fibres, each of which
on contraction swells up into a spindle shape. A mass of such fibres
aggregated together constitutes a muscle, and every muscle is attached
at either extremity, by means of a tendon, to a bone. Both extremities
of a muscle are never attached to the same bone--otherwise the muscle
would be absolutely useless. Usually there is only a single bone
between the two ends of a muscle, but in exceptional cases there may be
more. As a rule, the main body of a muscle lies along the bone to which
one end of it is attached, the other end of the muscle being attached
to the contiguous bone placed not far from the point. The first bone,
then, serves as a fulcrum on which the second bone moves as a lever,
and, as already pointed out, the familiar laws of the lever operate
here as fully as in the inanimate world. But a moment's reflection
will make it clear that the object effected by this mechanism is the
increase of motion with relative loss of energy. In other words, the
muscular force is applied to the short end of the lever, and a far
greater expenditure of force is required when the muscle contracts than
the power externally manifested would seem to indicate.
A moment's consideration of the mechanism of the arm, having regard to
the biceps muscle which flexes the elbow, will make this clear. If a
weight is held in the hand it is perhaps twelve inches from the elbow.
If, while holding the weight, you will grasp the elbow with the other
hand, you will feel the point of attachment of the biceps, and discover
that it does not seem to be, roughly speaking, more than about an inch
from the joint. Obviously, then, if you are lifting a pound weight, the
actual equivalent of energy expended by the contracting biceps must
be twelve pounds. But, in the meantime, when the pound weight in your
hand moves through the space of one inch, the muscle has contracted by
one-twelfth of an inch; and you may sweep the weight through a distance
of two feet by utilizing the two-inch contraction, which represents
about the capacity of the muscle.
A similar consideration of the muscles of the legs will show how the
muscular system which is susceptible of but trifling variation in size,
gives to the animal great locomotive power. With the aid of a series of
levers, represented by the bones of our thighs, legs, and feet, we are
able to stride along, covering three or four feet at each step, while
no set of the muscles that effect this propulsion varies in length by
more than two or three inches. It appears, then, that the muscular
system gives a marvelous illustration of capacity for storing energy in
a compact form and utilizing it for the development of motion.
THE TWO TYPES OF MUSCLES
The muscles of animals and men alike are divided into two systems,
one called voluntary, the other involuntary. The voluntary muscles,
as their name implies, are subject to the influence of the will,
and under ordinary conditions contract in response to the voluntary
nervous impulses. Certain sets of them, indeed, as those having to
do with respiration, have developed a tendency to rhythmical action
through long use, and ordinarily perform their functions without
voluntary guidance. Their function may, however, become voluntary
when attention is directed toward it, and is then subject to the
action of the will within certain bounds. Should a voluntary attempt
be made, however, to prevent their action indefinitely, the so-called
reflex mechanism presently asserts itself. All of which may be easily
attested by anyone who will attempt to stop breathing. All systems of
voluntary muscles are subject to the influence of habit, and may assume
activities that are only partially recognized by consciousness. As an
illustration in point, the muscles involved in walking come, in the
case of every adult, to perform their function without direct guidance
of the will. Such was not the case, however, in the early stage of
their development, as the observation of any child learning to walk
will amply demonstrate. In the case of animals, however, even those
muscles are so under the impress of hereditary tendencies as to perform
their functions spontaneously almost from the moment of birth. These,
however, are physiological details that need not concern us here. It
suffices to recall that the voluntary muscles may be directed by the
will, and indeed are always under what may be termed subconscious
direction, even when the conscious attention is not directed to them.
The strictly involuntary muscles, however, are placed absolutely beyond
control of the will. The most important of these muscles are those
that constitute the heart and the diaphragm, and that enter into the
substance of the walls of blood vessels, and of the abdominal organs.
It is obvious that the functioning of these important organs could not
advantageously be left to the direction of the will; and so, in the
long course of evolution they have learned, as it were, to take care
of themselves, and in so doing to take care of the organism, to the
life of which they are so absolutely essential. As the physiologist
views the matter, no organism could have developed which did not
correspondingly develop such involuntary action of the vital organs.
It will be seen that the involuntary muscles differ from the voluntary
muscles in that they are not connected with bones. Instead of being
thus attached to solid levers, they are annular in structure, and in
contracting virtually change the size of the ring which their substance
constitutes. Each fibre in contracting may be thought of as pulling
against other fibres, instead of against a bony surface, and the joint
action changes the size of the organ, as is obvious in the pulsing of
the heart.
Though the rhythmical contractions of the involuntary muscles are
independent of voluntary control, it must not be supposed that they
are independent of the control of the central nervous mechanism. On
the contrary, the nerve supply sent out from the brain to the heart
and to the abdominal organs is as plentiful and as important as that
sent to the voluntary muscles. There is a centre in the brain scarcely
larger than the head of a pin, the destruction of which will cause the
heart instantly to cease beating forever. From this centre, then, and
from the other centres of the brain, impulses are constantly sent to
the involuntary muscles, which determine the rate of activity. Nor are
these centres absolutely independent of the seat of consciousness, as
anyone will admit who recalls the varied changes in the heart's action
under stress of varying emotions.
That the voluntary muscles are controlled by the central nervous
mechanism needs no proof beyond the appeal to our personal experiences
of every moment. You desire some object that lies on the table in front
of you, and immediately your hand, thanks to the elaborate muscular
mechanism, reaches out and grasps it. And this act is but typical of
the thousand activities that make up our every-day life. Everyone is
aware that the channel of communication between the brain and the
muscular system is found in a system of nerves, which it is natural
now-a-days to liken to a system of telegraph wires. We speak of the
impulse generated in the brain as being transmitted along the nerves to
the muscle, causing that to contract. We are even able to measure the
speed of transfer of such an impulse. It is found to move with relative
slowness, compassing only about one hundred and twelve feet per second,
being in this regard very unlike the electric current with which it is
so often compared. But the precise nature of this impulse is unknown.
Its effect, however, is made tangible in the muscular contraction
which it is its sole purpose to produce. The essential influence of
the nerve impulse in the transaction is easily demonstrable; for if
the nerve cord is severed, as often happens in accidents, the muscle
supplied by that nerve immediately loses its power of voluntary
contraction. It becomes paralyzed, as the saying is.
THE NATURE OF MUSCULAR ACTION
Paying heed, now, to the muscle itself, it must be freely admitted
that, in the last analysis, the activities of the substance are as
mysterious and as inexplicable as are those involved in the nervous
mechanism. It is easy to demonstrate that what we have just spoken
of as a muscle fibre consists in reality of a little tube of liquid
protoplasm, and that the change in shape of this protoplasm constitutes
the contraction of which we are all along speaking. But just what
molecular and atomic changes are involved in this change of form of the
protoplasm, we cannot say. We know that the power to contract is the
one universal attribute of living protoplasm. This power is equally
wonderful and equally inexplicable, whether manifested in the case
of the muscle cell or in the case of such a formless single-celled
creature as the amoeba. When we know more of molecular and atomic
force, we may perhaps be able to form a mental picture of what goes on
in the structure of protoplasm when it thus changes the shape of its
mass. Until then, we must be content to accept the fact as being the
vital one upon which all the movements of animate creatures depend.
But if, here as elsewhere, the ultimate activities of molecules and
atoms lie beyond our ken, we may nevertheless gain an insight into
the nature of the substances involved. We know, for example, that the
chief constituents of all protoplasm are carbon, hydrogen, oxygen, and
nitrogen; and that with these main elements there are traces of various
other elements such as iron, sulphur, phosphorus, and sundry salts.
We know that when the muscle contracts some of these constituents
are disarranged through what is spoken of as chemical decomposition,
and that there results a change in the substance of the protoplasm,
accompanied by the excretion of a certain portion of its constituents,
and by the liberation of heat. Carbonic acid gas, for example, is
generated and is swept away from the muscular tissues in the ever
active bloodstreams, to be carried to the lungs and there expelled--it
being a noxious poison, fatal to life if retained in large quantities.
Equally noxious are other substances such as uric acid and its
compounds, which are also results of the breaking down of tissue that
attends muscular action. In a word, there is an incessant formation of
waste products, due to muscular activity, the removal of which requires
the constant service of the purifying streams of blood and of the
various excretory organs.
But this constant outflow of waste products from the muscle
necessitates, of course, in accordance with the laws of the
conservation of matter and of energy, an equally constant supply
of new matter to take the place of the old. This supply of what is
virtually fuel to be consumed, enabling the muscle to perform its
work, is brought to the muscle through the streams of blood which flow
from the heart in the arterial channels, and in part also through the
lymphatic system. The blood itself gains its supply from the digestive
system and from the lungs. The digestive system supplies water, that
all-essential diluent, and a great variety of compounds elaborated into
the proper pabulum; while the vital function of the lungs is to supply
oxygen, which must be incessantly present in order that the combustion
which attends muscular activity may take place. What virtually happens
is that fuel is sent from the digestive system to be burned in the
muscular system, with the aid of oxygen brought from the lungs.
In this view, the muscular apparatus is a species of heat engine. In
point of fact, it is a curiously delicate one as regards the range of
conditions within which it is able to act. The temperature of any given
organism is almost invariable; the human body, for example, maintains
an average temperature of 98-2/5 degrees, Fahrenheit. The range of
variation from this temperature in conditions of health is rarely
more than a fraction of a degree; and even under stress of the most
severe fever the temperature never rises more than about eight degrees
without a fatal result. That an organism which is producing heat in
such varying quantities through its varying muscular activities should
maintain such an equilibrium of temperature, would seem one of the most
marvelous of facts, were it not so familiar.
The physical means by which the heat thus generated is rapidly given
off, on occasion, to meet the varying conditions of muscular activity,
is largely dependent upon the control of the blood supply, in which
involuntary muscles, similar to those of the heart, are concerned.
In times of great muscular activity, when the production of heat is
relatively enormous, the arterioles that supply the surface of the
body are rapidly dilated so that a preponderance of blood circulates
at the surface of the body, where it may readily radiate its heat into
space; the vast system of perspiratory ducts, with which the skin is
everywhere supplied, aiding enormously in facilitating this result,
through the secretion of a film of perspiration, which in evaporating
takes up large quantities of heat.
The flushed, perspiring face of a person who has violently exercised
gives a familiar proof of these physiological changes; and the contrary
condition, in which the peripheral circulation is restricted, and in
which the pores are closed, is equally familiar. Moreover, the same
cutaneous mechanism is efficient in affording the organism protection
from the changes of external temperature; though the human machine,
thanks to the pampering influence of civilization, requires additional
protection in the form of clothing.
APPLICATIONS OF MUSCULAR ENERGY
Having thus outlined the conditions under which the muscular machine
performs its work, we have now to consider briefly the external
mechanisms with the aid of which muscular energy is utilized.
Of course, the simplest application of this power, and the one
universally employed in the animal world is that in which a direct
push or pull is given to the substance, the position of which it
is desired to change. We have already pointed out that there is no
essential difference between pushing and pulling. The fact receives
another illustration in considering the muscular mechanism. We speak
of pushing when we propel something away from a body, of pulling when
we draw something toward it, yet, as we have just seen, each can be
accomplished merely through the contraction of a set of muscles, acting
on differently disposed levers. All the bodily activities are reducible
to such muscular contractions, and the diversified movements in which
the organism constantly indulges are merely due to the large number and
elaborate arrangement of the bony levers upon which these muscles are
operated.
We may well suppose that the primitive man continued for a long
period of time to perform all such labors as he undertook without
the aid of any artificial mechanism; that is to say, without having
learned to gain any power beyond that which the natural levers
of his body provided. A brief observation of the actions of a
man performing any piece of manual labor will, however, quickly
demonstrate how ingeniously the bodily levers are employed, and how
by shifting positions the worker unconsciously makes the most of a
given expenditure of energy. By bending the arms and bringing them
close to the body, he is able to shorten his levers so that he can
lift a much greater weight than he could possibly raise with the arms
extended. On the other hand, with the extended arm he can strike a
much more powerful blow than with the shorter lever of the flexed
arm. But however ingenious the manipulation of the natural levers, a
full utilization of muscular energy is possible only when they are
supplemented with artificial aids, which constitute primitive pieces of
machinery.
These aids are chiefly of three types, namely, inclined planes,
friction reducers, and levers. The use of the inclined plane was very
early discovered and put into practise in chipped implements, which
took the form of the wedge, in such modifications as axes, knives, and
spears of metal. All of these implements, it will be observed, consist
essentially of inclined planes, adapted for piercing relatively soft
tissues of wood or flesh, and hence serving purposes of the greatest
practical utility.
The knife-blade is an extremely thin wedge, to be utilized by force of
pushing, without any great aid from acquired momentum. The hatchet, on
the other hand--and its modification the axe--has its blunter blade
fastened to a handle; that the principle of the wedge may be utilized
at the long end of a lever and with the momentum of a swinging blow.
Ages before anyone could have explained the principle involved in such
obscuring terms as that, the implement itself was in use for the same
purpose to which it is still applied. Indeed, there is probably no
other implement that has played a larger part in the history of human
industry. Even in the Rough Stone Age it was in full favor, and the
earliest metallurgists produced it in bronze and then in iron. The
blade of to-day is made of the best tempered steel, and the handle
or helve of hickory is given a slight curve that is an improvement on
the straight handle formerly employed; but on the whole it may be said
that the axe is a surviving primitive implement that has held its own
and demonstrated its utility in every generation since the dawn, not of
history only, but of barbarism, perhaps even of savagery.
The saw, consisting essentially of a thin elongated blade, one ragged
or toothed edge, is a scarcely less primitive and an equally useful and
familiar application of the principle of the inclined plane--though it
requires a moment's reflection to see the manner of application. Each
tooth, however minute, is an inclined plane, calculated to slide over
the tissue of wood or stone or iron even, yet to tear at the tissue
with its point, and, with the power of numbers, ultimately wear it away.
THE WHEEL AND AXLE
The primitive friction reducer, which continues in use to the present
day unmodified in principle, is the wheel revolving on an axle.
Doubtless man had reached a very high state of barbarism before he
invented such a wheel. The American Indian, for example, knew no
better method than to carry his heavy burdens on his shoulders, or
drag them along the ground, with at most a pair of parallel poles or
runners to modify the friction; every move representing a very wasteful
expenditure of energy. But the pre-historic man of the old world had
made the wonderful discovery that a wheel revolving on an axle vastly
reduces the friction between a weight and the earth, and thus enables
a man or a woman to convey a load that would be far beyond his or her
unaided powers. It is well to use both genders in this illustration,
since among primitive peoples it is usually the woman who is the bearer
of burdens. And indeed to this day one may see the women of Italy and
Germany bearing large burdens on their backs and heads, and dragging
carts about the streets, quite after the primitive method.
The more one considers the mechanism, the more one must marvel at the
ingenuity of the pre-historic man who invented the wheel and axle. Its
utility is sufficiently obvious once the thing has been done. In point
of fact, it so enormously reduces the friction that a man may convey
ten times the burden with its aid that he can without it. But how was
the primitive man, with his small knowledge of mechanics, to predict
such a result? In point of fact, of course, he made no such prediction.
Doubtless his attention was first called to the utility of rolling
bodies by a chance observation of dragging a burden along a pebbly
beach, or over rolling stones. The observation of logs or round stones
rolling down a hill might also have stimulated the imagination of some
inventive genius.
[Illustration: A BELGIAN MILK-WAGON.
In many of the countries of Europe the dog plays an important part as
a beast of burden. Stringent laws are enforced in these countries to
prevent possible abuse or neglect of the animals.]
Probably logs placed beneath heavy weights, such as are still employed
sometimes in moving houses, were utilized now and again for many
generations before the idea of a narrow section of a log adjusted on
an axis was evolved. But be that as it may, this idea was put into
practise before the historic period begins, and we find the earliest
civilized races of which we have record--those, namely, of Old Egypt
and of Old Babylonia--in full possession of the principle of the wheel
as applied to vehicles. Modern mechanics have, of course, improved the
mechanism as regards details, but the wheels depicted in Old Egyptian
and Babylonian inscriptions are curiously similar to the most modern
types. Indeed, the wheel is a striking illustration of a mechanism
which continued century after century to serve the purposes of the
practical worker, with seemingly no prospect of displacement.
MODIFIED LEVERS
For the rest, the mechanisms which primitive man learned early to
use in adding to his working efficiency, and which are still used by
the hand laborer, are virtually all modifications of our familiar
type-implement, the lever. A moment's reflection will show that the
diversified purposes of the crowbar, hoe, shovel, hammer, drill,
chisel, are all accomplished with the aid of the same principles.
The crowbar, for example, enables man to regain the power which he
lost when his members were adapted to locomotion. His hands, left
to themselves, as we have already pointed out, give but inadequate
expression to the power of his muscles. But by grasping the long end of
such a lever as the crowbar, he is enabled to utilize his entire weight
in addition to his muscular strength, and, with the aid of this lever,
to lift many times his weight.
The hoe, on the other hand, becomes virtually a lengthened arm,
enabling a very slight muscular motion to be transformed into the
long sweep of the implement, so that with small expenditure of energy
the desired work is accomplished. Similarly, the sledge and the axe
lengthen out the lever of the arms, so that great momentum is readily
acquired, and with the aid of inertia a relatively enormous force can
be applied. It will be observed that a laborer in raising a heavy
sledge brings the head of the implement near his body, thus shortening
the leverage and gaining power at the expense of speed; but extends his
arms to their full length as the sledge falls, having now the aid of
gravitation, to gain the full advantage of the long arm of the lever in
acquiring momentum.
Even such elaborately modified implements as the treadmill and the
rowboat are operated on the principle of the lever. These also are
mechanisms that have come down to us from a high antiquity. Their
utility, however, has been greatly decreased in modern times, by
the substitution of more elaborate and economical mechanisms for
accomplishing their respective purposes. The treadmill, indeed--which
might be likened to an overshot waterwheel in which the human foot
supplied the place of the falling water in giving power--has become
obsolete, though a modification of it, to be driven by animal power, is
still sometimes used, as we shall see in a moment.
All these are illustrations of mechanisms with the aid of which human
labor is made effective. They show the devices by which primitive man
used his ingenuity in making his muscular system a more effective
machine for the performance of work. But perhaps the most ingenious
feat of all which our primitive ancestor accomplished was in learning
to utilize the muscular energy of other animals. Of course the example
was always before him in the observed activity of the animals on every
side. Nevertheless, it was doubtless long before the idea suggested
itself, and probably longer still before it was put into practise, of
utilizing this almost inexhaustible natural supply of working energy.
DOMESTICATED ANIMALS
The first animal domesticated is believed to have been the dog, and
this animal is still used, as everyone knows, as a beast of burden in
the far North, and in some European cities, particularly in those of
Germany. Subsequently the ox was domesticated, but it is probable that
for a vast period of time it was used for food purposes, rather than as
a beast of burden. And lastly the horse, the worker _par excellence_,
was made captive by some Asiatic tribes having the genius of invention,
and in due course this fleetest of carriers and most efficient of
draught animals was introduced into all civilized nations.
Doubtless for a long time the energy of the horse was utilized in an
uneconomical way, through binding the burden on its back, or causing it
to drag the burden along the ground. But this is inferential, since,
as we have seen, the wheel was invented in pre-historic times, and at
the dawn of history we find the Babylonians driving harnessed horses
attached to wheeled vehicles. From that day to this the method of
using horse-power has not greatly changed. The vast majority of the
many millions of horses that are employed every day in helping on the
world's work, use their strength without gain or loss through leverage,
and with only the aid of rolling friction to increase their capacity as
beasts of burden.
To a certain extent horse-power is still used with the aid of the
modified treadmill just referred to--consisting essentially of an
inclined plane of flexible mechanism made into an endless platform,
which the horse causes to revolve as he goes through the movements of
walking upon it. In agricultural districts this form of power is still
sometimes used to run threshing machines, cider mills, wood-saws,
and the like. Another application of horse-power to the same ends
is accomplished through harnessing a horse to a long lever like the
spoke of a wheel, fastened to an axis, which is made to revolve as the
horse walks about it. Several horses are sometimes hitched to such
a mechanism, which becomes then a wheel of several spokes. But this
mechanism, which was common enough in agricultural districts two or
three decades ago, has been practically superseded in recent years by
the perambulatory steam engine.
[Illustration: TWO APPARATUSES FOR THE UTILIZATION OF ANIMAL POWER.
The upper figure shows the type of portable horse-power machine used
for threshing grain in 1851. The lower figure is an inclined-plane
horse-gear. The horse stands on the sloping platform tied to the bar in
front, so that it is compelled to walk as the platform recedes.]
It is obvious that the amount of work which a horse can accomplish
must vary greatly with the size and quality of the horse, and with the
particular method by which its energy is applied. For the purposes
of comparison, however, an arbitrary amount of work has been fixed
upon as constituting what is called a horse-power. This amount is the
equivalent of raising thirty-three thousand pounds of weight to the
height of one foot in one minute. It would be hard to say just why this
particular standard was fixed upon, since it certainly represents more
than the average capacity of a horse. It is, however, a standard which
long usage (it was first suggested by Watt, of steam-engine fame) has
rendered convenient, and one which the machinist refers to constantly
in speaking of the efficiency of the various types of artificial
machines. All questions of the exact legitimacy of this particular
standard aside, it was highly appropriate that the labor of the horse,
which has made up so large a share of the labor of the past, and which
is still so extensively utilized, should continue to be taken as the
measuring standard of the world's work.
IV
THE WORK OF AIR AND WATER
The store of energy contained in the atmosphere and in the waters of
the globe is inexhaustible. Its amount is beyond all calculation; or if
it were vaguely calculated the figures would be quite incomprehensible
from their very magnitude. It is not, however, an altogether simple
matter to make this energy available for the purposes of useful work.
We find that throughout antiquity comparatively little use was made of
either wind or water in their application to machinery.
Doubtless the earliest use of air as a motive power was through the
application of sails to boats. We know that the Phoenicians used a
simple form of sail, and no doubt their example was followed by all the
maritime peoples of subsequent periods. But the use of the sail even by
the Phoenicians was as a comparatively unimportant accessory to the
galaxies of oars, which formed the chief motive power. The elaboration
of sails of various types, adequate in extent to propel large ships,
and capable of being adjusted so as to take advantage of winds blowing
from almost any quarter, was a development of the Middle Ages.
The possibilities of work with the aid of running water were also but
little understood by the ancients. In the days of slave labor it was
scarcely worth while to tax man's ingenuity to invent machines, since
so efficient a one was provided by nature. Yet the properties of both
air and water were studied by various mechanical philosophers, at the
head of whom were Archimedes, whose work has already been referred to,
and the famous Alexandrian, Ctesibius, whose investigations became
familiar through the publications of his pupil, Hero.
Perhaps the most remarkable device invented by Ctesibius was a
fire-engine, consisting of an arrangement of valves constituting a
pump, and operating on the principle which is still in vogue. It is
known, however, that the Egyptians of a much earlier period used
buckets having valves in their bottoms, and these perhaps furnished the
foundation for the idea of Ctesibius. It is unnecessary to give details
of this fire-engine. It may be noted, however, that the principle of
the lever is the one employed in its operation to gain power. A valve
consists essentially of any simple hinged substance, arranged so that
it may rise or fall, alternately opening and closing an aperture.
A mere flap of leather, nailed on one edge, serves as a tolerably
effective valve. At least one of the valves used by Ctesibius was a
hinged piece of smooth metal. A piston fitted in a cylinder supplies
suction when the lever is raised, and pressure when it is compressed,
alternately opening the valve and closing the valve through which the
water enters the tube. Meantime a second valve alternating with the
first permits the water to enter the chamber containing air, which
through its elasticity and pressure equalizes the force of the stream
that is ejected from the chamber through the hose.
SUCTION AND PRESSURE
In the construction of this and various other apparatus, Ctesibius and
Hero were led to make careful studies of the phenomena of suction. But
in this they were not alone, since numerous of their predecessors had
studied the subject, and such an apparatus as the surgeon's cupping
glass was familiarly known several centuries before the Christian era.
The cupping glass, as perhaps should be explained to the reader of the
present day--since the apparatus went out of vogue in ordinary medical
practise two or three generations ago--consists of a glass cup in which
the air is exhausted, so as to suck blood from any part of the surface
of a body to which it is applied. Hero describes a method of exhausting
air by which such suction may be facilitated. But neither he nor any
other philosopher of his period at all understood the real nature of
this suction, notwithstanding their perfect familiarity with numerous
of its phenomena. It was known, for example, that when a tube closed
at one end is filled with water and inverted with the open end beneath
the surface of the water, the water remains in the tube, although one
might naturally expect that it would obey the impulses of gravitation
and run out, leaving the tube empty. A familiar explanation of this and
allied phenomena throughout antiquity was found in the saying that
"Nature abhors a vacuum." This explanation, which of course amounts
to no explanation at all, is fairly illustrative of the method of
metaphysical word-juggling that served so largely among the earlier
philosophers in explanation of the mysteries of physical science.
The real explanation of the phenomena of suction was not arrived
at until the revival of learning in the seventeenth century. Then
Torricelli, the pupil of Galileo, demonstrated that the word suction,
as commonly applied, had no proper application; and that the phenomena
hitherto ascribed to it were really due to the pressure of the
atmosphere. A vacuum is merely an enclosed space deprived of air, and
the "abhorrence" that Nature shows to such a space is due to the fact
that air has weight and presses in every direction, and hence tends
to invade every space to which it can gain access. It was presently
discovered that if the inverted tube in which the water stands was
made high enough, the water will no longer fill it, but will sink to a
certain level. The height at which it will stand is about thirty feet;
above that height a vacuum will be formed, which, for some reason,
Nature seems not to abhor. The reason is that the weight of any given
column of water about thirty feet in height is just balanced by the
weight of a corresponding column of atmosphere. The experiments that
gave the proof of this were made by the famous Englishman, Boyle. He
showed that if the heavy liquid, mercury, is used in place of water,
then the suspended column will be only about thirty inches in height.
The weight or pressure of the atmosphere at sea level, as measured by
these experiments, is about fifteen pounds to the square inch.
Boyle's further experiments with the air and with other gases developed
the fact that the pressure exerted by any given quantity of gas is
proportional to the external pressure to which it is subjected, which,
after all, is only a special application of the law that action and
reaction are equal. The further fact was developed that under pressure
a gas decreases at a fixed rate in bulk. A general law, expressing
these facts in the phrase that density and elasticity vary inversely
with the pressure in a precise ratio, was developed by Boyle and the
Frenchman, Mariotte, independently, and bears the name of both of its
discoverers. No immediate application of the law to the practical
purposes of the worker was made, however, and it is only in recent
years that compressed air has been extensively employed as a motive
power. Even now it has not proved a great commercial success, because
other more economical methods of power production are available. In
particular cases, however, it has a certain utility, as a relatively
large available source of energy may be condensed into a very small
receptacle.
A very striking experiment illustrating the pressure of the air was
made by a famous contemporary of Boyle and Mariotte, by the name of
Otto von Guericke. He connected an air pump with a large brass sphere,
composed of two hemispheres, the edges of which fitted smoothly, but
were not connected by any mechanism. Under ordinary conditions the
hemispheres would fall apart readily, but von Guericke proved, by
a famous public demonstration, that when the air was exhausted in
the sphere, teams of horses pulling in opposite directions on the
hemispheres could not separate them. This is famous as the experiment
of the Magdeburg spheres, and it is often repeated on a smaller scale
in the modern physical laboratory, to the astonishment of the tyro in
physical experiments.
The first question that usually comes to the mind of anyone who has
personally witnessed such an experiment, is the question as to how
the human body can withstand the tremendous force to which it is
subjected by an atmosphere exerting a pressure of fifteen pounds on
every square inch of its surface. The explanation is found in the
uniform distribution of the pressure, the influence of which is thus
counteracted, and by the fact that the tissues themselves contain
everywhere a certain amount of air at the same pressure. The familiar
experiment of holding the hand over an exhausted glass cylinder--which
experiment is indeed but a modification of the use of the cupping
glass above referred to--illustrates very forcibly the insupportable
difficulties which the human body would encounter were not its entire
surface uniformly subjected to the atmospheric pressure.
AIR IN MOTION
At about the time when the scientific experiments with the pressure of
gases were being made, practical studies of the effects of masses of
air in motion were undertaken by the Dutch philosopher, Servinus. The
use of the windmill in Holland as a means of generating power doubtless
suggested to Servinus the possibility of attaching a sail to a land
vehicle. He made the experiment, and in the year 1600 constructed a
sailing car which, propelled by the wind, traversed the land to a
considerable distance, on one occasion conveying a company of which
Prince Maurice of Orange was a member. But his experiments have seldom
been repeated, and indeed their lack of practical feasibility scarcely
needs demonstration.
The utility of the wind, however, in generating the power in a
stationary mechanism is familiar to everyone. Windmills were
constructed at a comparatively early period, and notwithstanding all
the recent progress in the development of steam and electrical power,
this relatively primitive so-called prime mover still holds its own in
agricultural districts, particularly in its application to pumps. A
windmill consists of a series of inclined planes, each of which forms
one of the radii of a circle, or spokes of a wheel, to the axle of
which a gearing is adjusted by which the power generated is utilized.
The wheel is made to face the wind by the wind itself blowing against a
sort of rudder which projects from the axis. The wind blowing against
the inclined surfaces or vanes of the wheel causes each vane to move in
accordance with the law of component forces, thus revolving the wheel
as a whole.
[Illustration: WINDMILLS OF ANCIENT AND MODERN TYPES.
The smaller figures show Dutch windmills of the present day, many of
which are identical in structure with the windmills of the middle ages.
It will be seen that the sails can be furled when desired to put the
mill out of operation. In the mill of modern type (large figure) the
same effect is produced by slanting the slats of the wheel.]
It has been affirmed that the Romans had windmills, but "the silence of
Vitruvius, Seneca, and Chrysostom, who have spoken of the advantages of
the wind, makes this opinion questionable." It has been supposed by
other writers that windmills were used in France in the sixth century,
while still others have maintained that this mechanism was unknown in
Europe until the time of the Crusades. All that is tolerably certain
is that in the twelfth century windmills were in use in France and
England. It is recorded that when they began to be somewhat common
Pope Celestine III. determined that the tithes of them belonged to the
clergy.
INHERENT DEFECTS OF THE WINDMILL
The mediæval European windmill was supplied with great sails of cloth,
and its picturesque appearance has been made familiar to everyone
through the famous tale of _Don Quixote_. The modern windmill, acting
on precisely the same principle, is a comparatively small affair,
comprising many vanes of metal, and constituting a far more practical
machine. The great defect of all windmills, however, is found in the
fact that of necessity they furnish such variable power, since the
force of the wind is incessantly changing. Worst of all, there may be
protracted periods of atmospheric calm, during which, of course, the
windmill ceases to have any utility whatever. This ineradicable defect
relegates the windmill to a subordinate place among prime movers, yet
on the other hand, its cheapness insures its employment for a long time
to come, and the industry of manufacturing windmills continues to be an
important one, particularly in the United States.
RUNNING WATER
The aggregate amount of work accomplished with the aid of the wind is
but trifling, compared with that which is accomplished with the aid of
water. The supply of water is practically inexhaustible, and this fluid
being much more manageable than air, can be made a far more dependable
aid to the worker. Every stream, whatever its rate of flow, represents
an enormous store of potential energy. A cubic foot of water weighs
about sixty-two and a half pounds. The working capacity of any mass
of water is represented by one-half its weight into the square of its
velocity; or, stated otherwise, by its weight into the distance of its
fall. Now, since the interiors of the continents, where rivers find
their sources, are often elevated by some hundreds or even thousands
of feet, it follows that the working energy expended--and for the most
part wasted--by the aggregate water current of the world is beyond all
calculation. Meantime, however, a portion of the energy which in the
aggregate represents an enormous working power is utilized with the aid
of various types of water wheels.
Watermills appear to have been introduced in the time of Mithridates,
Julius Cæsar, and Cicero. Strabo informs us that there was a watermill
near the residence of Mithridates; and we learn from Pomponius Sabinus,
that the first mill seen at Rome was erected on the Tiber, a little
before the time of Augustus. That they existed in the time of Augustus
is obvious from the description given of them by Vitruvius, and the
epigram of Antipater, who is supposed to have lived in the time of
Cicero. But though mills driven by water were introduced at this early
period, yet public mills did not appear till the time of Honorius and
Arcadius. They were erected on three canals, which conveyed water to
the city, and the greater number of them lay under Mount Janiculum.
When the Goths besieged Rome in 536, and stopped the large aqueduct and
consequently the mills, Belisarius appears to have constructed, for the
first time, floating mills upon the Tiber. Mills driven by the tide
existed at Venice in the year 1046, or at least in 1078.
The older types of water wheel are exceedingly simple in construction,
consisting merely of vertical wheels revolving on horizontal axes,
and so placed as to receive the weight or pressure of the water on
paddles or buckets at their circumference. The water might be allowed
to rush under the wheel, thus constituting an under-shot wheel; or
more commonly it flows from above, constituting an over-shot wheel.
Where the natural fall is not available, dams are employed to supply an
artificial fall.
This primitive type of water wheel has been practically abandoned
within the last generation, its place having been taken by the much
more efficient type of wheel known as the turbine. This consists of
a wheel, usually adjusted on a vertical axis, and acting on what is
virtually the principle of a windmill. To gain a mental picture of the
turbine in its simplest form, one might imagine the propelling screw
of a steamship, placed horizontally in a tube, so that the water could
rush against its blades. The tiny windmills which children often make
by twisting pieces of paper illustrate the same principle. Of course,
in its developed form the turbine is somewhat elaborated, in the aim to
utilize as large a proportion of the energy of the falling water as is
possible; but the principle remains the same.
The turbine wheel was invented by a Frenchman named Fourneyron, about
three-quarters of a century ago (1827), but its great popularity, in
America in particular, is a matter of the last twenty or thirty years.
To-day it has virtually supplanted every other type of water wheel.
To use any other is indeed a wasteful extravagance, as the perfected
turbine makes available more than eighty per cent. of the kinetic
energy of any mass of falling water. A turbine wheel two feet in
diameter is able to do the work of an enormous wheel of the old type.
Turbine wheels are of several types, one operating in a closed tube to
which air has no access, and another in an open space in the presence
of air. The water may also be made to enter the turbine at the side
or from below, thus serving to support the weight of the mechanism--a
consideration of great importance in the case of such gigantic turbines
as those that are employed at Niagara Falls, which we shall have
occasion to examine in detail in a later chapter.
[Illustration: WATER WHEELS.
Fig. 1 shows a model of the so-called breast wheel, a familiar type of
water wheel that has been in use since the time of the Romans. Figs.
2 and 3 show similar wheels as used to-day in Belgium. Fig. 4 shows a
model of Fourneyron's turbine. This wheel was made in 1837, but the
original turbine was introduced by Fourneyron in 1827. The turbine
wheel has now almost supplanted the other forms of water wheel except
in rural districts.]
The power generated by a revolution of the turbine wheel may, of
course, be utilized directly by belts or gearings attached to its
axle, or it may be transferred to a distance, with the aid of a
dynamo generating electricity. The latter possibility, which has only
recently been developed, and which we shall have occasion to examine
in detail in connection with our studies of the power at Niagara, gives
a new field of usefulness to the turbine wheel, and makes it probable
that this form of power will be vastly more used in the future than
it has been in the past. Indeed, it would not be surprising were it
ultimately to become the prime source of working energy as utilized in
every department of the world's work.
Mr. Edward H. Sanborn, in an article on Motive Power Appliances in the
Twelfth Census Report of the United States, comments upon the recent
advances in the use of water wheels as follows:
"One notable advance in turbine construction has been the production
of a type of wheel especially designed for operating under much higher
heads of water than were formerly considered feasible for wheels of
this type. Turbines are now built for heads ranging from 100 to 1,200
feet, and quite a number of wheels are in operation under heads of from
100 to 200 feet. This is an encroachment upon the field occupied almost
exclusively by wheels variously known as the 'impulse,' 'impact,'
'tangential,' or 'jet' type, the principle of which is the impact of
a powerful jet of water from a small nozzle upon a series of buckets
mounted upon the periphery of a small wheel."
"The impact water wheel," Mr. Sanborn continues, "has come largely
into use during the last ten years, principally in the far West,
where higher heads of water are available than can be found in other
parts of the country. With wheels of this type, exceedingly simple
in construction and of comparatively small cost, a large amount of
power is developed with great economy under the great heads that are
available. With the tremendous water pressure developed by heads of
1,000 feet and upward, which in many cases are used for this purpose,
wheels of small diameter develop an extraordinary amount of power.
To the original type of impact wheel which first led the field have
been added several styles embodying practically the same principle.
Considerable study has been given to the designing of buckets with a
view to securing free discharge and the avoidance of any disturbing
eddies, and important improvements have resulted from the thorough
investigation of the action of the water during, and subsequent to,
its impact on the buckets. The impact wheel has been adapted to a wide
range of service with great variation as to the conditions under which
it operates, wheels having been made in California from 30 inches to
30 feet in diameter, and to work under heads ranging from 35 to 2,100
feet, and at speeds ranging from 65 to 1,100 revolutions per minute. A
number of wheels of this type have been built with capacities of not
less than 1,000 horse-power each."
HYDRAULIC POWER
A few words should be said about the familiar method of transmitting
power with the aid of water, as illustrated by the hydrostatic press.
This does not indeed utilize the energy of the water itself, but it
enables the worker to transmit energy supplied from without, and to
gain an indefinite power to move weights through a short distance,
with the expenditure of very little working energy. The principle on
which the hydrostatic press is based is the one which was familiar to
the ancient philosophers under the name of the hydrostatic paradox.
It was observed that if a tube is connected with a closed receptacle,
such as a strong cask, and cask and tube are filled with water, the
cask will presently be burst by the pressure of the water, provided the
tube is raised to a height, even though the actual weight of water in
the tube be comparatively slight. A powerful cask, for example, may be
burst by the water poured into a slender pipe. The result seems indeed
paradoxical, and for a long time no explanation of it was forthcoming.
It remained for Servinus, whose horseless wagon is elsewhere noticed,
to discover that the water at any given level presses equally in all
directions, and that its pressure is proportionate to its depth, quite
regardless of its bulk. Then, supposing the tube in our experiment to
have a cross-section of one square inch, a pressure equal to that in
the tube would be transmitted to each square inch of the surface of the
cask; and the pressure might thus become enormous.
If, instead of a tube lifted to a height, the same tube is connected
with a force pump operated with a lever--an apparatus similar to the
fire-engine of Ctesibius--it is obvious that precisely the same effect
may be produced; whatever pressure is developed in the piston of the
force pump, similar pressure will be transferred to a corresponding
area in the surface of the cask or receptacle with which the force pump
connects. In practise this principle is utilized, where great pressure
is desired, by making a receptacle with an enormous piston connecting
with the force pump just described.
An indefinite power may thus be developed, the apparatus constituting
virtually a gigantic lever. But the principle of the equivalence of
weight and distance still holds, precisely as in an actual lever,
and while the pressure that may be exerted with slight expenditure
of energy is enormous, the distance through which this pressure acts
is correspondingly small. If, for example, the piston of the force
pump has an area of one square inch, while the piston of the press
has an area of several square feet, the pressure exerted will be
measured in tons, but the distance through which it is exerted will be
almost infinitesimal. The range of utility of the hydrostatic press
is, therefore, limited, but within its sphere, it is an incomparable
transmitter of energy.
[Illustration: HYDRAULIC PRESS AND HYDRAULIC CAPSTAN.
The upper figure shows Bramah's original hydraulic pump and press,
now preserved in the South Kensington Museum, London. The machine was
constructed in 1796 by Joseph Bramah to demonstrate the principle of
his hydraulic press. The discrepancy in size between the small lever
worked by hand and the enormous lever carrying a heavy weight gives a
vivid impression of the gain in power through the use of the apparatus.
The lower figure shows the hydraulic capstan used on many modern ships,
in which the same principle is utilized.]
Moreover, it is possible to reverse the action of the hydraulic
apparatus so as to gain motion at the expense of power. A familiar type
of elevator is a case in point. The essential feature of the hydraulic
elevator consists of a ram attached to the bottom of the elevator and
extending down into a cylinder, slightly longer than the height to
which the elevator is to rise. The ram is fitting into a cylinder with
water-tight packing, or a cut leather valve. Water under high pressure
is admitted to the cylinder through the valve at the bottom, and the
pressure thus supplied pushes up the ram, carrying the elevator with
it, of course. Another valve allows the water to escape, so that ram
and elevator may descend, too rapid descent being prevented by the
partial balancing of ram and elevator with weights acting over pulleys.
The ram, to the end of which pressure is thus applied, need be but a
few inches in diameter. Water pressure is secured by bringing water
from an elevation. Such an elevator acts slowly, but is a very safe
and in many ways satisfactory mechanism. Such elevators are still used
extensively in Europe, but have been almost altogether displaced in
America by the electric elevator.
The hydraulic elevator just described is virtually a water engine, the
ram acting as piston. A veritable engine, of small size, to perform
any species of mechanical work, may be constructed on precisely the
same principle, the piston in this case acting in a cylinder similar to
that of the ordinary steam engine. Such an engine operates slowly but
with great power. It has special utility where it is desirable to apply
power intermittently, as in various parts of a dockyard, or in handling
guns and ammunition on shipboard. In the former case in particular,
it is often inconvenient to use steam power, as steam sent from a
central boiler condenses in a way to interfere with its operation. In
such a case any number of small water-pressure engines may be operated
from a single tank where water is at a high elevation, or where the
requisite pressure is secured artificially. In the latter case, the
water is kept under pressure by a large piston or ram heavily weighted,
the entire receptacle being, of course, of water-tight construction
and adapted to withstand pressure. The pump that supplies the tank is
ordinarily made to work automatically, ceasing operation as soon as the
ram rises to the top of the receptacle, and beginning again whenever,
through use of water, the ram begins to descend. Such an apparatus is
called an accumulator. Such water engines have come into vogue only in
comparatively recent times, being suggested by the steam engine. As
already pointed out, their utility is restricted, yet the total number
of them in actual use to-day is large, and their share in the world's
work is not altogether inconsiderable.
V
CAPTIVE MOLECULES: THE STORY OF THE STEAM ENGINE
We come now to that all-important transformer of power, the steam
engine. Everybody knows that steam is a state of water in which,
under the influence of heat, the molecules have broken away from the
mutual attraction of cohesion, and are flying about at inconceivable
speed, rebounding from one another after collision, in virtue of their
elasticity, exerting in the aggregate an enormous pressure in every
direction. It is this consideration of the intimate character of steam
that justifies the title of the present chapter; a title that has
further utility as drawing a contrast between the manner of working
with which we are now to be concerned, and the various types of workers
that we have previously considered.
In speaking of the animal machine and of work accomplished by the air
and the water, we have been concerned primarily with masses of matter,
possessing and transmitting energy. Of course molecules--since they
make up the substance of all matter--could not be altogether ignored,
but in the main we have had to do with molar rather than with molecular
motion. Now, however, we are concerned with a mechanism in which the
molecular activities are directly concerned in performing work.
Even in the aggregate the molecules make up a mere intangible gas,
which requires to be closely confined in order that its energy may be
made available. Once the molecules have performed their work, they
are so changed in their activities that they sink back, as it were,
exhausted, into a relatively quiescent state, which enables their
latent cohesive forces to reduce them again to the state of a liquid.
In a word, we are concerned with the manifestation of energy which
depends upon molecular activities in a way quite different from what
has been the case with any of the previously considered mechanisms.
The tangible manifestation of energy which we term heat is not merely
a condition of action and a by-product, as it was in the case of
the animal machine; it is the essential factor upon which all the
efficiency of the mechanism depends.
It should perhaps be stated that this explanation of the action of
the steam engine is a comparatively modern scientific interpretation.
The earlier experimenters brought the steam engine to a high state of
efficiency, without having any such conception as this of the nature
of steam itself. For practical purposes it suffices to note that water
when heated takes the form of steam; that this steam has the property
of powerful and indefinite expansion; and thirdly, that when allowed to
escape from a state of pressure, sudden expansion of the steam cools it
sufficiently to cause the recondensation of part of its substance, thus
creating a vacuum.
Stated in few words, the entire action of the steam depends upon these
simple mechanical principles. The principles are practically applied
by permitting the steam to enter the cylinder where it can act on
a piston, to which it gives the thrust that is transmitted to an
external mechanism by means of a rod attached to the piston. When the
piston has been driven to the end of the desired thrust, the valve is
opened automatically, permitting the steam to escape, thus producing a
vacuum, and insuring the return thrust of the piston, which is further
facilitated, ordinarily, by the admission of steam to the other side
of the piston. Practical operation of this mechanism is familiar to
everyone, though the marvel of its power and efficiency seems none the
less because of its familiarity.
It is not too much to say that this relatively simple device, in its
first general application, marked one of the most important turning
points in the history of civilization. To its influence, more than to
any other single cause, must be ascribed the revolutionary change that
came over the character of practical life in the nineteenth century.
From prehistoric times till well toward the close of the eighteenth
century, there was scarcely any important change in carrying out the
world's work. And in the few generations that have since elapsed, the
entire aspect of the mechanical world has been changed, the working
efficiency of the individual has been largely increased; mechanical
tasks have become easy which hitherto were scarcely within the range of
human capacity.
Before we go on to the detailed study of the machine which has produced
these remarkable results, it is desirable to make inquiry as to the
historical development of so important an invention.
The practical steam engine in its modern form dates, as just mentioned,
from the latter part of the eighteenth century, and was perfected by
James Watt, who is commonly thought of as being its inventor. In point
of fact, however, the history of most inventions is duplicated here, as
on examination it appears that various forerunners of Watt had been on
the track of the steam engine, and some of them, indeed, had produced a
workable machine of no small degree of efficiency.
The very earliest experiments were made away back in the Alexandrian
days in the second century before the Christian era, the experimenter
being the famous Hero, whose work in an allied field was referred to
in the preceding chapter. Hero produced--or at least described and so
is credited with producing, though the actual inventor may have been
Ctesibius--a little toy mechanism, in which a hollow ball was made to
revolve on an axis through the agency of steam, which escaped from
two bent tubes placed on opposite sides of the ball, their orifices
pointing in opposite directions. The apparatus had no practical
utility, but it sufficed to establish the principle that heat, acting
through the agency of steam, could be made to do mechanical work. Had
not the age of Hero been a time of mental stasis, it is highly probable
that the principle he had thus demonstrated would have been applied
to some more practical mechanism in succeeding generations. As it
was, however, nothing practical came of his experiment, and the steam
turbine engine was remembered only as a scientific toy.
No other worker continued the experiments, so far as is known, until
the time of the great Italian, Leonardo da Vinci, who, late in the
fifteenth century, gave a new impulse to mechanical invention. Leonardo
experimented with steam, and succeeded in producing what was virtually
an explosion engine, by the agency of which a ball was propelled along
the earth. But this experiment also failed to have practical result.
BEGINNINGS OF MODERN DISCOVERY
Such sporadic experiments as these have no sequential connection with
the story of the evolution of the steam engine. The experiments which
led directly on to practical achievements were not begun until the
seventeenth century. In the very first year of that century, an Italian
named Giovanni Battista della Porta published a treatise on pneumatics,
in which the idea of utilizing steam for the practical purpose of
raising water was expressly stated. The idea of this inventor was put
into effect in 1624 by a French engineer and mathematician, Solomon de
Caus. He invented two different machines, the first of which required a
spherical boiler having an internal tube reaching nearly to the bottom;
a fire beneath the boiler produced steam which would force the water in
the boiler to a height proportional to the pressure obtained. In the
other machine, steam is led from the boiler into the upper part of a
closed cistern containing water to be elevated. To the lower portion of
the cistern a delivery pipe was attached so that water was discharged
under a considerable pressure. This arrangement was precisely similar
to the apparatus employed by Hero of Alexandria in various of his
fountains, as regards the principle of expanding gas to propel water.
An important difference, however, consists in the fact that the
scheme of della Porta and of de Caus embodied the idea of generating
pressure with the aid of steam, whereas Hero had depended merely on the
expansive property of air compressed by the water itself.
While these mechanisms contained the germ of an idea of vast
importance, the mechanisms themselves were of trivial utility. It is
not even clear whether their projectors had an idea of the properties
of the condensation of vapor, upon which the working of the practical
steam engine so largely depends. This idea, however, was probably
grasped about half a century later by an Englishman, Edward Somerset,
the celebrated Marquis of Worcester, who in 1663 described in his
_Century of Inventions_ an apparatus for raising water by the expansive
force of steam. His own account of his invention is as follows:
"An admirable and most forcible way to drive up water by fire; not by
drawing or sucking it upwards, for that must be as the philosopher
calleth it, _intra sphæram activitatis_, which is but at such a
distance. But this way hath no bounder, if the vessel be strong enough:
for I have taken a piece of whole cannon, whereof the end was burst,
and filled it three-quarters full of water, stopping and screwing up
the broken end, as also the touch-hole; and making a constant fire
under it, within twenty-four hours it burst and made a great crack; so
that having a way to make my vessels so that they are strengthened by
the force within them, and the one to fill after the other, I have seen
the water run like a constant stream, forty feet high: one vessel of
water, rarefied by fire, driveth up forty of cold water; and the man
that tends the work is but to turn two cocks, that one vessel of water
being consumed, another begins to force and refill with cold water,
and so successively; the fire being tended and kept constant, which
the self-same person may likewise abundantly perform in the interim,
between the necessity of turning the said cocks."
It is unfortunate that the Marquis did not give a more elaborate
description of this remarkable contrivance. The fact that he treats it
so casually is sufficient evidence that he had no conception of the
possibilities of the mechanism; but, on the other hand, his description
suffices to prove that he had gained a clear notion of, and had
experimentally demonstrated, the tremendous power of expansion that
resides in steam. No example of his steam pump has been preserved, and
historians of the subject have been left in doubt as to some details
of its construction, and in particular as to whether it utilized the
principle of a vacuum created through condensation of the steam.
THOMAS SAVERY'S STEAM PUMP
This principle was clearly grasped, however, by another Englishman,
Thomas Savery, a Cornish mine captain, who in 1698 secured a patent for
a steam engine to be applied to the raising of water, etc. A working
model of this machine was produced before the Royal Society in 1699.
The transactions of the Society contain the following: "June 14th,
1699, Mr. Savery entertained the Royal Society with showing a small
model of his engine for raising water by help of fire, which he set to
work before them: the experiment succeeded according to expectation,
and to their satisfaction."
The following very clear description of Savery's engine is given in the
introduction to Beckmann's _History of Inventions_:
"This engine, which was used for some time to a considerable extent for
raising water from mines, consisted of a strong iron vessel shaped like
an egg, with a tube or pipe at the bottom, which descended to the place
from which the water was to be drawn, and another at the top, which
ascended to the place to which it was to be elevated. This oval vessel
was filled with steam supplied from a boiler, by which the atmospheric
air was first blown out of it. When the air was thus expelled and
nothing but pure steam left in the vessel, the communication with the
boiler was cut off, and cold water poured on the external surface. The
steam within was thus condensed and a vacuum produced, and the water
drawn up from below in the usual way by suction. The oval vessel was
thus filled with water; a cock placed at the bottom of the lower pipe
was then closed, and steam was introduced from the boiler into the
oval vessel above the surface of the water. This steam being of high
pressure, forced the water up the ascending tube, from the top of
which it was discharged, and the oval vessel being thus refilled with
steam, the vacuum was again produced by condensation, and the same
process was repeated. By using two oval steam vessels, which would act
alternately--one drawing water from below, while the other was forcing
it upwards, an uninterrupted discharge of water was produced. Owing to
the danger of explosion, from the high pressure of the steam which was
used, and from the enormous waste of heat by unnecessary condensation,
these engines soon fell into disuse."
[Illustration: THOMAS SAVERY'S STEAM ENGINE.
The principle involved is that of the expansion of steam exerting a
propulsive force and its subsequent condensation to produce a vacuum.
These are the principles employed in the modern steam engine, but the
only use to which they were put in Savery's engine was the elevation of
water by suction.]
This description makes it obvious that Savery had the clearest
conception of the production of a vacuum by the condensation of steam,
and of the utilization of the suction thus established (which suction,
as we know, is really due to the pressure of outside air) to accomplish
useful work. Savery also arranged this apparatus in duplicate, so that
one vessel was filling with water while the other was forcing water
to the delivery pipe. This is credited with being the first useful
apparatus for raising water by the combustion of fuel. There was a
great waste of steam, through imparting heat to the water, but the
feasibility of the all-important principle of accomplishing mechanical
labor with the aid of heat was at last demonstrated.
As yet, however, the experimenters were not on the track of the
method by which power could be advantageously transferred to outside
machinery. An effort in quite another direction to accomplish this
had been made as early as 1629 by Giovanni Branca, an Italian
mathematician, who had proposed to obtain rotary motion by allowing
a jet of steam to blow against the vanes of a fan wheel, capable of
turning on an axis. In other words, he endeavored to utilize the
principle of the windmill, the steam taking the place of moving air.
The idea is of course perfectly feasible, being indeed virtually that
which is employed in the modern steam turbine; but to put the idea
into practise requires special detailed arrangements of steam jet and
vanes, which it is not strange the early inventor failed to discover.
His experiments appear not to have been followed up by any immediate
successor, and nothing practical came of them, nor was the principle
which he had attempted to utilize made available until long after a
form of steam engine utilizing another principle for the transmission
of power had been perfected.
DENIS PAPIN INVENTS THE PISTON ENGINE
The principle in question was that of causing expanding steam to press
against a piston working tightly in a cylinder, a principle, in short,
with which everyone is familiar nowadays through its utilization in
the ordinary steam engine. The idea of making use of such a piston
appears to have originated with a Frenchman, Denis Papin, a scientific
worker, who, being banished from his own country, was established as
professor of mathematics at the University of Marburg. He conceived the
important idea of transmitting power by means of a piston as early as
1688, and about two years later added the idea of producing a vacuum in
a cylinder, by cooling the cylinder,--the latter idea being, as we have
just seen, the one which Savery put into effect.
[Illustration: DIAGRAMS OF EARLY ATTEMPTS TO UTILIZE THE POWER OF
STEAM. GIOVANNI BRANCA 1629 GUILLAUME AMONTONS 1699 Two attempts
to give rotation to a mechanical apparatus through the action of
heated air or steam. Nothing practical came of either effort, but the
mechanisms depicted are of historical interest.]
It will be noted that Papin's invention antedated that of Savery; to
the Frenchman, therefore, must be given the credit of hitting upon two
important principles which made feasible the modern steam engine. Papin
constructed a model consisting of a small cylinder in which a solid
piston worked. In the cylinder beneath the piston was placed a small
quantity of water, which, when the cylinder was heated, was turned
into steam, the elastic force of which raised the piston. The cylinder
was then cooled by removing the fire, when the steam condensed, thus
creating a vacuum in the cylinder, into which the piston was forced by
the pressure of the atmosphere.
Such an apparatus seems crude enough, yet it incorporates the essential
principles, and required but the use of ingenuity in elaborating
details of the mechanism, to make a really efficient steam engine.
It would appear, however, that Papin was chiefly interested in the
theoretical, rather than in the really practical side of the question,
and there is no evidence of his having produced a working machine of
practical power, until after such machines worked by steam had been
constructed elsewhere.
THOMAS NEWCOMEN'S IMPROVED ENGINE
As has happened so often in other fields, Englishmen were the first
to make practical use of the new ideas. In 1705 Thomas Newcomen, a
blacksmith or ironmonger, and John Cawley, a plumber and glazier,
patented their atmospheric engine, and five years later, in the year
1710, namely, Newcomen had on the market an engine which is described
in the _Report of the Department of Science and Arts of the South
Kensington Museum_, as "the first real pumping engine ever made."
The same report describes the engine as "a vertical steam cylinder
provided with a piston connected at one end of the beam, having a
pivot or bearing in the middle of its length, and at the other end of
the beam pump rods for working the pump. The cylinder was surrounded
by a second cylinder or jacket, open at the top, and cold water could
be supplied to this outer cylinder at pleasure. The single or working
cylinder could be supplied with steam when desired from a boiler below
it. There was a drain pipe from the bottom of the working cylinder,
and one from the outer cylinder. For the working of the engine steam
was admitted to the working cylinder, so as to fill it and expel all
the air, the piston then being at the top, owing to the weight of the
pump rods being sufficient to lift it; then the steam was shut off and
the drain cocks closed and cold water admitted to the outer cylinder,
so that the steam in the working cylinder condensed, and, leaving a
partial vacuum of pressure of the atmosphere, forced the piston down
and drew up the pump rods, thus making a stroke of the pump. Then the
water was drawn off from the outer cylinder and steam admitted to the
working cylinder before allowing the piston to return to the top of its
stroke, ready for the next down stroke."
It will be observed that this machine adopts the principle, with only
a change of mechanical details, of the Papin engine just described. A
later improvement made by Newcomen did away with the outer cylinder
for condensing the steam, employing instead an injection of cold water
into the working cylinder itself, thus enabling the engine to work more
quickly. It is said that the superiority of the internal condensing
arrangement was accidentally discovered through the improved working
of an engine that chanced to have an exceptionally leaky piston or
cylinder. Many engines were made on this plan and put into practical
use.
Another important improvement was made by a connection from the beam
to the cocks or valves, so that the engine worked automatically,
whereas in the first place it had been necessary to have a boy or man
operate the valves,--a most awkward arrangement, in the light of modern
improvements. As the story is told, the duty of opening and closing
the regulating and condensing valves was intrusted to boys called
cock boys. It is said that one of these boys named Humphrey Potter
"wishing to join his comrades at play without exposing himself to the
consequences of suspending the performance of the engine, contrived, by
attaching strings of proper length to the levers which governed the two
cocks, to connect them with the beam, so that it should open and close
the cocks as it moved up and down with the most perfect regularity."
This story has passed current for almost two centuries, and it has been
used to point many a useful moral. It seems almost a pity to disturb
so interesting a tradition, yet it must have occurred to more than one
iconoclast that the tale is almost too good to be true. And somewhat
recently it has been more than hinted that Desaguliers, with whom the
story originated, drew upon his imagination for it. A print is in
existence, made so long ago as 1719, representing an engine erected
by Newcomen at Dudley Castle, Staffordshire, in 1712, in which an
automatic valve gear is clearly shown, proving that the Newcomen engine
was worked automatically at this early period. That the admirable
story of the inventive youth, whose wits gave him leisure for play,
may not be altogether discredited, however, it should be added that
unquestionably some of the early engines had a hand-moved gear, and
that at least one such was still working in England after the middle of
the nineteenth century. It seems probable, then, that the very first
engines were without the automatic valve gear, and there is no inherent
reason why a quick-witted youth may not have been the first to discover
and remedy the defect.
According to the Report of the Department of Science and Arts of
the South Kensington Museum: "The adoption of Newcomen's engine was
rapid, for, commencing in 1711 with the engine at Wolverhampton, of
twenty-three inch diameter and six foot stroke, they were in common use
in English collieries in 1725; and Smeaton found in 1767 that, in the
neighborhood of Newcastle alone there were fifty-seven at work, ranging
in size from twenty-eight inch to seventy-five inch cylinder diameter,
and giving collectively about twelve hundred horse-power. As Newcomen
obtained an evaporation of nearly eight pounds of water per pound of
coal, the increase of boiler efficiency since his time has necessarily
been but slight, although in other requisites of the steam generator
great improvements are noticeable."
[Illustration: A MODEL OF THE NEWCOMEN ENGINE.
This engine has particular interest not only because it was a practical
pumping engine, but also because it was while repairing an engine of
this type that Watt was led to the experiments that resulted in his
epoch-making discovery.]
THE COMING OF JAMES WATT
The Newcomen engine had low working efficiency as compared with the
modern engine; nevertheless, some of these engines are still used in a
few collieries where waste coal is available, the pressure enabling the
steam to be generated in boilers unsafe for other purposes. The great
importance of the Newcomen engine, however, is historical; for it was
while engaged in repairing a model of one of these engines that James
Watt was led to invent his plan of condensing the steam, not in the
working cylinder itself, but in a separate vessel,--the principle upon
which such vast improvements in the steam engine were to depend.
It is impossible to overestimate the importance of the work which Watt
accomplished in developing the steam engine. Fully to appreciate it,
we must understand that up to this time the steam engine had a very
limited sphere of usefulness. The Newcomen engine represented the
most developed form, as we have seen; and this, like the others that
it had so largely superseded, was employed solely for the pumping of
water. In the main, its use was confined to mines, which were often
rendered unworkable because of flooding. We have already seen that a
considerable number of engines were in use, yet their power in the
aggregate added but a trifle to man's working efficiency, and the work
that they did accomplish was done in a most uneconomical manner. Indeed
the amount of fuel required was so great as to prohibit their use in
many mines, which would have been valuable could a cheaper means have
been found of freeing them from water. Watt's inventions, as we shall
see, accomplished this end, as well as various others that were not
anticipated.
It was through consideration of the wasteful manner of action of the
steam engine that Watt was led to give attention to the subject.
The great inventor was a young man at the University of Glasgow. He
had previously served an apprenticeship of one year with a maker of
philosophical instruments in London, but ill health had prevented him
from finishing his apprenticeship, and he had therefore been prohibited
from practising his would-be profession in Glasgow. Finally, however,
he had been permitted to work under the auspices of the University;
and in due course, as a part of his official duties, he was engaged
in repairing a model of the Newcomen engine. This incident is usually
mentioned as having determined the line of Watt's future activity.
It should be recalled, however, that Watt had become a personal friend
of the celebrated Professor Black, the discoverer of latent heat, and
the foremost authority in the world, in this period, on the study of
pneumatics. Just what share Black had in developing Watt's idea, or
in directing his studies toward the expansive properties of steam,
it would perhaps be difficult to say. It is known, however, that the
subject was often under discussion; and the interest evinced in it by
Black is shown by the fact that he subsequently wrote a history of
Watt's inventions.
It is never possible, perhaps, for even the inventor himself to re-live
the history of the growth of an idea in his own mind. Much less is it
possible for him to say precisely what share of his progress has been
due to chance suggestions of others. But it is interesting, at least,
to recall this association of Watt with the greatest experimenter of
his age in a closely allied field. Questions of suggestion aside,
it illustrates the technical quality of Watt's mind, making it
obvious that he was no mere ingenious mechanic, who stumbled upon his
invention. He was, in point of fact, a carefully trained scientific
experimenter, fully equipped with all the special knowledge of his time
in its application to the particular branch of pneumatics to which he
gave attention.
The first and most obvious defect in the Newcomen engine was, as Watt
discovered, that the alternating cooling and heating of the cylinder
resulted in an unavoidable waste of energy. The apparatus worked, it
will be recalled, by the introduction of steam into a vertical cylinder
beneath the piston, the cylinder being open above the piston to admit
the air. The piston rod connected with a beam suspended in the middle,
which operated the pump, and which was weighted at one end in order
to facilitate the raising of the piston. The steam, introduced under
low pressure, scarcely more than counteracted the pressure of the air,
the raising of the piston being largely accomplished by the weight in
question.
Of course the introduction of the steam heated the cylinder. In order
to condense the steam and produce a vacuum, water was injected, the
cylinder being thereby cooled. A vacuum being thus produced beneath
the cylinder, the pressure of the air from above thrust the cylinder
down, this being the actual working agent. It was for this reason
that the Newcomen engine was called, with much propriety, a pneumatic
engine. The action of the engine was very slow, and it was necessary to
employ a very large piston in order to gain a considerable power.
The first idea that occurred to Watt in connection with the probable
improvement of this mechanism did not look to the alteration of any of
the general features of the structure, as regards size or arrangement
of cylinder, piston, or beam, or the essential principle upon which
the engine worked. His entire attention was fixed on the discovery
of a method by which the loss of heat through periodical cooling of
the cylinder could be avoided. We are told that he contemplated the
subject long, and experimented much, before he reached a satisfactory
solution. Naturally enough his attention was first directed toward the
cylinder itself. He queried whether the cylinder might not be made of
wood, which, through its poor conduction of heat, might better equalize
the temperature. Experiments in this direction, however, produced no
satisfactory result.
[Illustration: WATT'S EARLIEST TYPE OF PUMPING ENGINE.
The lower figure shows the ruins of Watt's famous engine "Old Bess."
The upper figure shows a reconstructed model of the "Old Bess" engine.
It will be noted that the walking beam is precisely of the Newcomen
type. In fact, the entire engine is obviously only a modification
of the Newcomen engine. It had, however, certain highly important
improvements, as described in the text.]
Then at last an inspiration came to him. Why not connect the cylinder
with another receptacle, in which the condensation of the steam could
be effected? The idea was a brilliant one, but neither its originator
nor any other man of the period could possibly have realized its vast
and all-comprehending importance. For in that idea was contained the
germ of all the future of steam as a motive power. Indeed, it scarcely
suffices to speak of it as the germ merely; the thing itself was
there, requiring only the elaboration of details to bring it to
perfection.
Watt immediately set to work to put his brilliant conception of the
separate condenser to the test of experiment. He connected the cylinder
of a Newcomen engine with a receptacle into which the steam could be
discharged after doing its work on the piston. The receptacle was
kept constantly cooled by a jet of water, this water and the water
of condensation, together with any air or uncondensed steam that
might remain in the receptacle, being constantly removed with the
aid of an air pump. The apparatus at once demonstrated its practical
efficiency,--and the modern steam engine had come into existence.
It was in the year 1765, when Watt was twenty-nine years old, that he
made his first revolutionary experiment, but his first patents were
not taken out until 1769, by which time his engine had attained a
relatively high degree of perfection. In furthering his idea of keeping
the cylinder at an even temperature, he had provided a covering for it,
which might consist of wood or other poorly conducting material, or a
so-called jacket of steam--that is to say, a portion of steam admitted
into the closed chamber surrounding the cylinder. Moreover, the
cylinder had been closed at the top, and a portion of steam admitted
above the piston, to take the place of the atmosphere in producing the
down stroke. This steam above the piston, it should be explained, did
not connect with the condensing receptacle, so the engine was still
single-acting; that is to say it performed work only during one stroke
of the piston. A description of the mechanism at this stage of its
development may best be given in the words of the inventor himself, as
contained in his specifications in the application for patent on his
improvements in 1769.
"My method of lessening the consumption of steam, and consequently
fuel, in fire-engines, consists of the following principles:
"First, That vessel in which the powers of steam are to be employed to
work the engine, which is called the cylinder in common fire-engines,
and which I call the steam vessel, must, during the whole time the
engine is at work, be kept as hot as the steam that enters it; first
by enclosing it in a case of wood, or any other materials that
transmit heat slowly; secondly, by surrounding it with steam or other
heated bodies; and, thirdly, by suffering neither water nor any other
substance colder than the steam to enter or touch it during that time.
"Secondly, In engines that are to be worked wholly or partially
by condensation of steam, the steam is to be condensed in vessels
distinct from the steam vessels or cylinders, although occasionally
communicating with them; these vessels I call condensers; and, whilst
the engines are working, these condensers ought at least to be kept as
cold as the air in the neighborhood of the engines, by application of
water or other cold bodies.
"Thirdly, Whatever air or other elastic vapor is not condensed by the
cold of the condenser, and may impede the working of the engine, is to
be drawn out of the steam vessels or condensers by means of pumps,
wrought by the engines themselves, or otherwise.
"Fourthly, I intend in many cases to employ the expansive force of
steam to press on the pistons, or whatever may be used instead of them,
in the same manner in which the pressure of the atmosphere is now
employed in common fire-engines. In cases where cold water can not be
had in plenty, the engines may be wrought by this force of steam only,
by discharging the steam into the air after it has done its office.
"Sixthly, I intend in some cases to apply a degree of cold not capable
of reducing the steam to water, but of contracting it considerably,
so that the engines shall be worked by the alternate expansion and
contraction of the steam.
"Lastly, Instead of using water to render the pistons and other parts
of the engine air-and steam-tight, I employ oils, wax, resinous bodies,
fat of animals, quicksilver and other metals in their fluid state."
ROTARY MOTION
It must be understood that Watt's engine was at first used exclusively
as an apparatus for pumping. For some time there was no practical
attempt to apply the mechanism to any other purpose. That it might
be so applied, however, was soon manifest, in consideration of the
relative speed with which the piston now acted. It was not until 1781,
however, that Watt's second patent was taken out, in which devices are
described calculated to convert the reciprocating motion of the piston
into motion of rotation, in order that the engine might drive ordinary
machinery.
It seems to be conceded that Watt was himself the originator of the
idea of making the application through the medium of a crank and
fly-wheel such as are now universally employed. But the year before
Watt took out his second patent, another inventor named James Picard
had patented this device of crank and connecting rod, having, it is
alleged, obtained the idea from a workman in Watt's employ. Whatever
be the truth as to this point, Picard's patent made it necessary for
Watt to find some alternative device, and after experimenting, he hit
upon the so-called sun and planet gearing, and henceforth this was used
on his rotary engines until the time for the expiration of Picard's
patent, after which the simpler and more satisfactory crank and
fly-wheel were adopted.
In the meantime, Watt had associated himself with a business partner
named Boulton, under the firm name of Boulton and Watt. In 1776 a
special act of legislation extending the term of Watt's original patent
for a period of twenty-five years had been secured. All infringements
were vigorously prosecuted, and the inventor, it is gratifying to
reflect, shared fully in the monetary proceeds that accrued from his
invention.
[Illustration: WATT'S ROTATIVE ENGINE.
The lower figure shows the earliest type of mechanism through which
Watt applied his engine to other uses than that of pumping. The
so-called sun-and-planet gearing, through which rotary motion was
attained, is seen at the lower right-hand corner of the figure. The
upper figure shows a later and much improved type of the Watt engine,
in which the sun-and-planet gearing has been supplanted by a simple
crank.]
Notwithstanding the early recognition of the possibility of securing
rotary motion with Watt's perfected Newcomen engine, it was long
before the full possibilities of the application of this principle
were realized, even by the most practical of machinists. Watt himself
apparently appreciated the possibilities no more fully than the
others, as the use of his famous engines "Beelzebub" and "Old Bess"
in the establishment of Boulton and Watt amply testifies. It appears
that Boulton had been an extensive manufacturer of ornamental metal
articles. To drive his machinery at Soho he employed two large water
wheels, twenty-four feet in diameter and six feet wide. These sufficed
for his purpose under ordinary conditions, but in dry weather from
six to ten horses were required to aid in driving the machinery. When
Watt's perfected engine was available, however, this was utilized to
pump water from the tail race back to the head race, that it might be
used over and over. "Old Bess" had a cylinder thirty-three inches in
diameter with seven-foot stroke, operating a pump twenty-four inches
in diameter; it therefore had remarkable efficiency as a pumping
apparatus. But of course it utilized, at best, only a portion of the
working energy contained in the steam; and the water wheels in turn
could utilize not more than fifty per cent. of the store of energy
which the pump transferred to the water in raising it. Therefore, such
use of the steam engine involved a most wasteful expenditure of energy.
It was long, however, before the practical machinists could be made to
believe that the securing of direct rotary power from the piston could
be satisfactorily accomplished. It was only after the introduction of
higher speed and heavier fly-wheels, together with improved governors,
that the speed of rotation was so equalized as to meet satisfactorily
the requirements of the practical engineer, and ultimately to displace
the wasteful method of securing rotary motion indirectly through the
aid of pump and water wheel. It may be added, that the centrifugal
governor, with which modern engines are provided to regulate their
speed, was the invention of Watt himself.
FINAL IMPROVEMENTS AND MISSED OPPORTUNITIES
In the year 1782 Watt took out patents which contained specifications
for the two additional improvements that constituted his final
contribution to the production of the steam engine. The first of these
provided for the connection of the cylinder chamber on each side of the
piston with the condenser, so that the engine became double acting. The
second introduced the very important principle,--from the standpoint of
economy in the use of steam--of shutting off the supply of steam from
the cylinder while the piston has only partially traversed its thrust,
and allowing the remainder of the thrust to be accomplished through
the expansion of the steam. The application of the first of these
principles obviously adds greatly to the efficiency of the engine, and
in practise it was found that the application of the second principle
produces a very great saving in steam, and thus adds materially to the
economical working of the engine.
All of Watt's engines continued to make use of the walking beam
attached to the piston for the transmission of power; and engineers
were very slow indeed to recognize the fact that in many--in fact in
most--cases this contrivance may advantageously be done away with. The
recognition of this fact constitutes one of the three really important
advances that have been made in the steam engine since the time of
Watt. The other two advances consist of the utilization of steam under
high pressure, and of the introduction of the principle of the compound
engine.
Neither of these ideas was unknown to Watt, since the utilization
of steam under high pressure was advocated by his contemporary,
Trevithick, while the compound engine was invented by another
contemporary named Hornblower. Perhaps the very fact that these rival
inventors put forward the ideas in question may have influenced Watt
to antagonize them; in particular since his firm came into legal
conflict with each of the other inventors. At any rate, Watt continued
to the end of his life to be an ardent advocate of low pressure for
the steam engine, and his firm even attempted to have laws passed
making it illegal--on the ground of danger to human life--to utilize
high-pressure steam, such as employed by Trevithick.
Possibly the conservatism of increasing age may also have had its
share in rendering Watt antagonistic to the new ideas; for he was
similarly antagonistic to the idea of applying steam to the purposes
of locomotion. Trevithick, among others, had, as we shall see in due
course, made such application with astonishing success, producing
a steam automobile which traversed the highway successfully. In
his earlier years Watt had conceived the same idea, and had openly
expressed his opinion that the steam engine might be used for this
purpose. But late in life he was so antipathetic to the idea that he
is said to have put a clause in the lease of his house, providing that
no steam carriage should under any pretext be allowed to approach it.
These incidents have importance as showing--as we shall see illustrated
again and again in other fields--the disastrous influence in retarding
progress that may be exercised by even the greatest of scientific
discoverers, when authority well earned in earlier years is exercised
in an unfortunate direction later in life. But such incidents as
these are inconsequential in determining the position among the
world's workers of the man who was almost solely responsible for the
transformation of the steam engine from an expensive and relatively
ineffective pumping apparatus, to the great central power that has ever
since moved the major part of the world's machinery.
THE SUPREME IMPORTANCE OF WATT
It is speaking well within bounds to say that no other invention
within historical times has had so important an influence upon the
production of property--which, as we have seen, is the gauge of the
world's work--as this invention of the steam engine. We have followed
the history of that invention in some detail, because of its supreme
importance. To the reader who was not previously familiar with that
history, it may seem surprising that after a lapse of a little over
a century one name and one alone should be popularly remembered in
connection with the invention; whereas in point of fact various workers
had a share in the achievement, and the man whose name is remembered
was among the last to enter the field. We have seen that the steam
engine existed as a practical working machine several decades before
Watt made his first invention; and that what Watt really accomplished
was merely the perfecting of an apparatus which already had attained a
considerable measure of efficiency.
There would seem, then, to be a certain lack of justice in ascribing
supreme importance to Watt in connection with the steam engine. Yet
this measure of injustice we shall find, as we examine the history of
various inventions, to be meted always by posterity in determining the
status of the men whom it is pleased to honor. One practical rule, and
one only, has always determined to whom the chief share of glory shall
be ascribed in connection with any useful invention.
The question is never asked as to who was the originator of the idea,
or who made the first tentative efforts towards its utilization,--or,
if asked by the historical searcher, it is ignored by the generality of
mankind.
So far as the public verdict, which in the last resort determines
fame, is concerned, the one question is, Who perfected the apparatus
so that it came to have general practical utility? It may be, and
indeed it usually is the case, that the man who first accomplished the
final elaboration of the idea, made but a comparatively slight advance
upon his predecessors; the early workers produced a machine that was
_almost_ a success; only some little flaw remained in their plans. Then
came the perfecter, who hit upon a device that would correct this last
defect,--and at last the mechanism, which hitherto had been only a
curiosity, became a practical working machine.
In the case of the steam engine, it might be said that even a smaller
feat than this remained to be accomplished when Watt came upon the
scene; since the Newcomen engine was actually a practical working
apparatus. But the all-essential thing to remember is that this
Newcomen engine was used for a single purpose. It supplied power for
pumping water, and for nothing else. Neither did it have possibilities
much beyond this, until the all-essential modification was suggested by
Watt, of exhausting its steam into exterior space.
This modification is in one sense a mere detail, yet it illustrates
once more the force of Michelangelo's famous declaration that trifles
make perfect; for when once it was tested, the whole practical
character of the steam engine was changed. From a wasteful consumer of
fuel, capable of running a pump at great expense, it became at once a
relatively economical user of energy, capable of performing almost any
manner of work.
Needless to say, its possibilities in this direction were not
immediately realized, in theory or in practise; yet the conquest that
it made of almost the entire field of labor resulted in the most
rapid transformation of industrial conditions that the world has ever
experienced. After all, then, there is but little injustice in that
public verdict which remembers James Watt as the inventor, rather than
as the mere perfecter, of the steam engine.
THE PERSONALITY OF JAMES WATT
The man who occupies this all-important position in the industrial
world demands a few more words as to his personality. His work we have
sufficiently considered, but before we pass on to the work of his
successors, it will be worth our while to learn something more of the
estimate placed upon the man himself. Let us quote, then, from some
records written by men who were of the same generation.
"Independently of his great attainments in mechanics, Mr. Watt was
an extraordinary and in many respects a wonderful man. Perhaps no
individual in his age possessed so much, or remembered what he had read
so accurately and well. He had infinite quickness of apprehension, a
prodigious memory, and a certain rectifying and methodizing power of
understanding which extracted something precious out of all that was
presented to it. His stores of miscellaneous knowledge were immense,
and yet less astonishing than the command he had at all times over
them. It seemed as if every subject that was casually started in
conversation had been that which he had been last occupied in studying
and exhausting; such was the copiousness, the precision, and the
admirable clearness of the information which he poured out upon it
without effort or hesitation. Nor was this promptitude and compass of
knowledge confined, in any degree, to the studies connected with his
ordinary pursuits.
"That he should have been minutely and extensively skilled in
chemistry, and the arts, and in most of the branches of physical
science, might, perhaps, have been conjectured; but it could not have
been inferred from his usual occupations, and probably is not generally
known, that he was curiously learned in many branches of antiquity,
metaphysics, medicine, and etymology, and perfectly at home in all
the details of architecture, music, and law. He was well acquainted,
too, with most of the modern languages, and familiar with their most
recent literature. Nor was it at all extraordinary to hear the great
mechanician and engineer detailing and expounding, for hours together,
the metaphysical theories of the German logicians, or criticizing the
measures or the matter of the German poetry.
"It is needless to say, that with those vast resources, his
conversation was at all times rich and instructive in no ordinary
degree. But it was, if possible, still more pleasing than wise, and
had all the charms of familiarity, with all the substantial treasures
of knowledge. No man could be more social in his spirit, less assuming
or fastidious in his manners, or more kind and indulgent towards
all who approached him. His talk, too, though overflowing with
information, had no resemblance to lecturing, or solemn discoursing;
but, on the contrary, was full of colloquial spirit and pleasantry.
He had a certain quiet and grave humor, which ran through most of his
conversation, and a vein of temperate jocularity, which gave infinite
zest and effect to the condensed and inexhaustible information which
formed its main staple and characteristic. There was a little air of
affected testiness, and a tone of pretended rebuke and contradiction,
which he used towards his younger friends, that was always felt by
them as an endearing mark of his kindness and familiarity, and prized
accordingly, far beyond all the solemn compliments that proceeded from
the lips of authority. His voice was deep and powerful; though he
commonly spoke in a low and somewhat monotonous tone, which harmonized
admirably with the weight and brevity of his observations, and set off
to the greatest advantage the pleasant anecdotes which he delivered
with the same grave tone, and the same calm smile playing soberly on
his lips.
[Illustration: JAMES WATT.]
"There was nothing of effort, indeed, or of impatience, any more than
of pride or levity, in his demeanor; and there was a finer expression
of reposing strength, and mild self-possession in his manner, than we
ever recollect to have met with in any other person. He had in his
character the utmost abhorrence for all sorts of forwardness, parade,
and pretension; and indeed never failed to put all such impostors out
of countenance, by the manly plainness and honest intrepidity of his
language and deportment.
"He was twice married, but has left no issue but one son, associated
with him in his business and studies, and two grandchildren by a
daughter who predeceased him. He was fellow of the Royal Societies both
of London and Edinburgh, and one of the few Englishmen who were elected
members of the National Institute of France. All men of learning and
of science were his cordial friends; and such was the influence of his
mild character, and perfect fairness and liberality, even upon the
pretender to these accomplishments, that he lived to disarm even envy
itself, and died, we verily believe, without a single enemy."
VI
THE MASTER WORKER
We have already pointed out at some length that, in the hands of Watt,
the steam engine came at once to be a relatively perfect apparatus, and
that only three really important modifications have been applied to it
since the day of its great perfecter. These modifications, as already
named, are the doing away with the walking beam, the utilization of
high pressure steam, and the development of the compound engine. Each
of these developments requires a few words of explanation.
The retention of the heavy walking beam for so long a time after the
steam engine of Watt had been applied to the various purposes of
machinery, illustrates the power of a pre-conceived idea. With the
Newcomen engine this beam was an essential, since it was necessary
to have a weight to assist in raising the piston. But with the
introduction of steam rather than air as the actual power to push the
piston, and in particular with the elaboration of the double-chamber
cylinder, with steam acting equally on either side of the piston, the
necessity for retaining this cumbersome contrivance no longer existed.
Yet we find all the engines made by Watt himself, and nearly all those
of his contemporaries, continuing to utilize this means of transmitting
the power of the piston. Even the road locomotive, as illustrated by
that first wonderful one of Trevithick's and such colliery locomotives
as "Puffing Billy" and "Locomotion," utilized the same plan. It was not
until almost a generation later that it became clear to the mechanics
that in many cases, indeed in most cases, this awkward means of
transmitting power was really a needlessly wasteful one, and that with
the aid of fly-wheel and crank-shaft the thrust of the piston might be
directly applied to the wheel it was destined to turn, quite as well as
through the intermediary channel of the additional lever.
The utility of the beam has, indeed, still commended it for certain
purposes, notably for the propulsion of side-wheel steamers, such as
the familiar American ferryboat. But aside from such exceptional uses,
the beam has practically passed out of existence.
There was no new principle involved in effecting this change. It was
merely another illustration of the familiar fact that it is difficult
to do things simply. As a rule, inventors fumble for a long time with
roundabout and complex ways of doing things, before a direct and simple
method occurs to them. In other words, the highest development often
passes from the complex to the simple, illustrating, as it were, an
oscillation in the great law of evolution. So in this case, even so
great an inventor as Watt failed to see the utility of doing away with
the cumbersome structure which his own invention had made no longer
a necessity, but rather a hindrance to the application of the steam
engine. However, a new generation, no longer under the thraldom of
the ideas of the great inventor, was enabled to make the change,
gradually, but in the end effectively.
HIGH-PRESSURE STEAM
As regards the use of steam under high pressure, somewhat the same
remarks apply, so far as concerns the conservatism of mankind, and
the influence which a great mind exerts upon its generation. Just why
Watt should have conceived an antagonism to the idea of high-pressure
steam is not altogether clear. It has been suggested, indeed, that
this might have been due to the fact that a predecessor of Watt had
invented a high-pressure engine which did not use the principle of
condensation, but exhausted the steam into open space. As early as
1725, indeed, Leupold in his _Theatrum Machinarum_, had described
such a non-condensing engine, which, had it been made practically
useful, would have required a high pressure of steam. Partly through
the influence of this work, perhaps, there came to be an association
between the words high pressure and non-condensing, so that these terms
are considered to be virtually synonymous; and since Watt's great
contribution consisted of an application of the idea of condensation,
he was perhaps rendered antagonistic to the idea of high pressure,
through this psychological suggestion. In any event, the antagonism
unquestionably existed in his mind; though it has often enough been
pointed out that this seems the more curious since high-pressure steam
would so much better have facilitated the application of that other
famous idea of Watt, the use of the expansive property of steam.
Curiously enough, however, the influence of Watt led to experiments
in high-pressure steam through an indirect channel. The contemporary
inventor, Trevithick, in connection with his partner, Bull, had made
direct-acting pumping engines with an inverted cylinder, fixed in line
with the pump rod, and actually dispensing with the beam. But as these
engines used a jet of cold water in the exhaust pipe to condense the
steam, Boulton and Watt brought suit successfully for infringement of
their patent, and thus prevented Trevithick from experimenting further
in that direction. He was obliged, therefore, to turn his attention to
a different method, and probably, in part at least, in this way was
led to introduce the non-condensing, relatively high-pressure engine.
This was used about the year 1800. At the same time somewhat similar
experiments were made by Oliver Evans in America.
Both Trevithick and Evans applied their engines to the propulsion of
road vehicles; and Trevithick is credited with being the first man
who ran a steam locomotive on a track,--a feat which he accomplished
as early as the year 1804. We are not here concerned with the details
of this accomplishment, which will demand our attention in a later
chapter, when we come to discuss the entire subject of locomotive
transportation. But it is interesting to recall that the possibilities
of the steam engine were thus early realized, even though another
generation elapsed before they were finally demonstrated to the
satisfaction of the public. It is particularly interesting to note that
in his first locomotive engine, Trevithick allowed the steam exhaust
to escape into the funnel of the engine to increase the draught,--an
expedient which was so largely responsible for Stephenson's success
with his locomotive twenty years later, and which retains its utility
in the case of the most highly developed modern locomotive.
Trevithick was, however, entirely subordinated by the great
influence of Watt, and the use of high pressure was in consequence
discountenanced by the leading mechanical engineers of England for some
decades. Meantime, in America, the initiative of Evans led to a much
earlier general use of high-pressure steam. In due course, however, the
advantages of steam under high pressure became evident to engineers
everywhere, and its conquest was finally complete.
The essential feature of super-heated steam is that it contains, as
the name implies, an excess of heat beyond the quantity necessary to
produce mere vaporization, and that the amount of water represented
in this vapor is not the maximum possible under given conditions. In
other words, the vapor is not saturated. It has been already explained
that the amount of vapor that can be taken up in a given space under a
given pressure varies with the temperature of the space. Under normal
conditions, when a closed space exists above a liquid, evaporation
occurs from the surface of the liquid until the space is saturated,
and no further evaporation can occur so long as the temperature and
pressure are unchanged. If now the same space is heated to a higher
degree, more vapor will be taken up until again the point of saturation
is attained. But, obviously, if the space were disconnected with the
liquid, and then heated, it would acquire a capacity to take up more
vapor, and so long as this capacity was latent, the vapor present would
exist in a super-heated condition.
[Illustration: OLD IDEAS AND NEW APPLIED TO BOILER CONSTRUCTION.
The lower figure shows Robert Trevithick's famous boiler, used in
operating his locomotive about the year 1804. The original is preserved
in the South Kensington Museum, London. The upper figure shows a modern
tubular boiler, by way of contrast.]
It will be understood from what has been said before, that with all
accessions of heat, the expansive power of the vapor is increased,--its
molecules becoming increasingly active; hence one of the very obvious
advantages of super-heated steam for the purpose of pushing a piston.
There are other advantages, however, which are not at first sight
so apparent, having to do with the properties of condensation. To
understand these, we must pay heed for a few moments to the changes
that take place in steam itself in the course of its passage through
the cylinder, where it performs its work upon the piston.
Many of these changes were not fully understood by the earlier
experimenters, including Watt. Indeed the theory of the steam engine,
or rather the general theory of the heat engine, was not worked out
until the year 1824, when the Frenchman Carnot took the subject in
hand, and performed a series of classical experiments, which led to a
nearly complete theoretical exposition of the subject. It remained,
however, for the students of thermo-dynamics, about the middle of the
nineteenth century, with Clausius and Rankine at their head, to perfect
the theory of the steam engine, and the general subject of the mutual
relations of heat and mechanical work.
We are not here concerned with any elaboration of details, but merely
with a few of the essential principles which enter practically into
the operation of the steam engine. It appears, then, that when steam
enters the cylinder and begins to thrust back the piston of the steam
engine, a portion of the steam is immediately condensed on the walls
of the cylinder, owing to the fact that previous condensation of steam
has cooled these walls to a certain extent. We have already pointed
out that Watt endeavored in his earlier experiments to overcome this
difficulty, by equalizing the temperature of the cylinder walls to the
greatest practicable extent.
Notwithstanding his efforts, however, and those of numberless later
experimenters, it still remains true that under ordinary conditions,
particularly if steam enters the cylinder at the saturation point,
a very considerable condensation occurs. Indeed this may amount to
from thirty to fifty per cent. of the entire bulk of water contained
in the quantity of steam that enters the cylinder. This condensation
obviously militates against the expansive or working power of the
steam. But now as the steam expands, pushing forward the cylinder, it
becomes correspondingly rarefied, and immediately a portion of the
condensed steam becomes again vaporized, and in so doing it takes up
a certain amount of heat and renders it latent. This disadvantageous
cycle of molecular transformations is very much modified in the case of
super-heated steam, for the obvious reason that such steam may be very
much below the saturation point, and hence requires a very much greater
lowering of temperature in order to produce condensation of any portion
of its mass. Without elaborating details, it suffices to note that in
all highly efficient modern engines, steam is employed at a relatively
high pressure, and that sometimes this pressure becomes enormous.
COMPOUND ENGINES
As to the compound engine, that also, as has been pointed out, was
invented by a contemporary of Watt, Jonathan Hornblower by name, whose
patent bears date of 1781. In Hornblower's engine, steam was first
admitted to a small cylinder, and then, after performing its work on
the piston, was allowed to escape, not into a condensing receptacle,
but into a larger cylinder where it performed further work upon another
piston. This was obviously an instance of the use of steam expansively,
and it has been pointed out that, in consequence, Hornblower was
the first to make use of this idea in practise, although it is said
that Watt's experiments had even at that time covered this field.
The application of the idea to the movement of the second cylinder,
however, appears to have been original with Hornblower. Certainly it
owed nothing to Watt, who refused to accept the idea, and continued
throughout his life to frown upon the compound engine.
Nevertheless, the device had great utility, as subsequent experiments
were very fully to demonstrate. The compound engine was revived by
Woolf in 1804, and his name rather than Hornblower's is commonly
associated with it. The latter experimenter demonstrated that the
compound engine has two important merits as against the simple engine.
One of these is that the sum of the two forces exerted by the joint
action results in a more even and continuous pressure throughout the
cycle than could be accomplished by the action of a single cylinder.
To understand this it must be recalled that when using the expansive
property of steam, the piston thrust could not possibly be uniform,
since the greatest pressure exerted by the steam would be exerted at
the moment before it was shut off from the boiler, and its pressure
must then decrease progressively, as it exerts more and more work upon
the piston and becomes more expanded, thus obviously retaining less
elastic energy. The operation of the fly-wheel largely compensates
this difference of pressure in practise, but it would be obviously
advantageous could the pressure be equalized; and, as just stated, the
compound engine tends to produce this result.
The second, and perhaps the more important merit of the compound
engine is, that it is found in practise to keep the cylinders at a
more uniform temperature. A moment's reflection makes it clear why
this should be the case, since in a single-cylinder engine the exhaust
connects with the cool condenser, whereas in the compound engine the
exhaust from the first cylinder connects with the second cylinder at
only slightly lower temperature.
In many modern engines a third cylinder and sometimes even a fourth
is added, constituting what are called respectively triple-expansion
and quadruple-expansion engines. The triple-expansion system is very
generally employed, especially where it is peculiarly desirable to
economize fuel, as, for example, in the case of ships.
[Illustration: COMPOUND ENGINES.
The lower figure illustrates the use of a modern compound engine,
directly operating the propeller shaft of a steamship. The middle
figure shows a similarly direct application of power to the axes of
paddle wheels. The upper figure shows the application of power through
a walking beam similar in principle to that of the original Newcomen
and Watt engines.]
ROTARY ENGINES
All these improvements, it will be observed, have to do with details
that do not greatly modify the steam engine from the original type. The
cylinder with its closely fitting piston, as introduced in the Newcomen
engine, is retained and constitutes the essential mechanism through
which the energy of steam is transferred into mechanical energy. But
from a comparatively remote period the idea has prevailed that it might
be possible to utilize a different principle; that, in short, if the
steam instead of being made to press against a piston were allowed
to rush against fan-like blades, adjusted to an axle, it might cause
blades and axle to revolve, precisely as a windmill is made to revolve
by the pressure of the wind, or the turbine wheel by the pressure of
water.
In a word, it has been believed that a turbine engine might be
constructed, which would utilize the energy of the steam as
advantageously as it is utilized in the piston engine, and at the same
time would communicate its power as a direct rotation, instead of as a
straight thrust that must be translated into a rotary motion by means
of a crank or other mechanism.
In point of fact, James Watt himself invented such an engine, and
patented it in 1782, th
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