a machine which a monk, afterwards Pope Sylvester II, was supposed
to have borrowed from Satan, though he was probably indebted for it
to the Saracens. For nearly nine hundred years after his day, the
best ingenuity of Italian, German, Swiss, French, and English
mechanics was devoted to perfecting this noble creation, and it
became at last a part of the civilized man, a sort of additional or
supplementary sense. The savage may well be excused for mistaking
the watch for a living creature. It could not serve us better, if it
were. True, it does not perform its function by its own force, but by
a stock of extraneous force which is from time to time put into a
little store-house called a spring. Neither does the living creature
perform its functions by any other force than that which is developed
by the chemical action within it, or the _quasi_ combustion of its
food. Its will does but direct the application of its mechanical
power. It creates none. You may weigh the animal and all the food it
is to consume, and thence calculate the utmost ounce of work, of a
given kind, which it can thereafter perform. It may do less, but
cannot do more. Having consumed all of its food and part of itself,
it dies. Its chemical organs have oxydated or burned up all the
combustibles submitted to them, thus developing a definite amount of
heat, a part of which, at the dictation of the will, by the
mechanism of nerves and muscles, has been converted into mechanical
motion. When the chemical function ceases, for the want of materials
to act upon, the development of heat ceases. There is no more either
to be converted into motion or to maintain the temperature of the
body; and self-consumption having already taken the place of
self-repair, there is no article left but the _articulus mortis_.
But of all the force or motion produced by, or rather passing through,
a living animal, or any other organism, none is ever, so far as we
know, annihilated. The motion which has apparently ceased or been
destroyed has in reality passed into heat, light, electricity,
magnetism, or other effect,--itself, perhaps, nothing but motion, to
keep on, in one form or another, indefinitely. The fuel which we put
into the stomach of the horse, of iron or of flesh, first by its
oxydation raises heat, a part of which it is the function of the
individual to convert into motion, to be expended on friction and
resistance, or, in other words, to be reconverted into heat. What
becomes of this heat, then? If the fuel were to be replaced or
deoxydated, the heat that originally came from the oxydation would be
precisely reabsorbed. But this heat of itself cannot overcome the
stronger affinity which now chains the fuel to the oxygen. It must
go forward, not backward, about its business, forever and ever. It
may pass, but not cease. The sharp-eyed Faraday has been following
far away this Proteus, with a strong suspicion that it changes at
last into gravity, in which shape it returns straight to the sun,
carrying down with it, probably, those flinty showers of meteors
which, striking fire in the atmosphere of the prime luminary,
replenish its overflowing fountain of life. But we are not aware
that he has yet discovered the anastomosis of this conversion, or
quite established the fact. We are therefore not yet quite ready to
resolve the universe of physical forces into the similitude of the
mythical mill-stream, which, flowing round a little hill, came back
and fed its own pond. Nevertheless, we believe the physicists have
pretty generally agreed to assume as a law of Nature what they call
the conservation of force, the principle we have been endeavoring to
explain.
Under the lead of this law, theory, or assumption, discoveries have
been made that deeply and practically interest the most abject
mortal who anywhere swings a hoe or shoulders a hod, as well as the
lords of the land. For example, it has been ascertained that heat is
converted into motion, or motion into heat, according to a fixed or
constant ratio or equivalent. To be more particular, the heat which
will raise the temperature of a pound of water one degree of
Fahrenheit's scale, when converted into mechanical motion, is
equivalent to the force which a weight of seven hundred and
seventy-two pounds would exert by falling one foot. This is a
wonderfully small quantity of heat to balance so heavy a blow, but
the careful experiments of Mr. Joule of Manchester, the discoverer,
confirmed by Regnault, Thomson, Rankine, Clausius, Mayer, Rennie,
and others, have, we believe, satisfied scientific men that it is
not far from the correct measure. Were the same, or a far less
amount of heat, concentrated on a minute chip of steel struck off by
collision with a flint, it would be visible to the eye as a spark,
and show us how motion is converted into light as well as heat.
It is not our vocation to dive into the infinities, either upward or
downward, in search, on the one hand, of the ultimate atoms of the
rarest ether, by whose vibrations the luminous waves run through
space at the rate of more than ten millions of miles a minute, or,
on the other, of the nebulous systems, worlds in the gristle, so far
off that the light just now arriving from them tells only how they
looked two hundred thousand years ago. All we have to say is, that,
if we do not now absolutely know, we do reasonably suspect, that heat
and light are mere mechanical motions, alike in nature and
interconvertible in fact. The luminiference seems to behave itself,
not like infinitely small bullets projected from Sharpe's rifles of
proportionately small bore, as was once supposed, but rather after
the manner of the sound-waves, which we know travel through the air
from the sonorous body to the ear. They have also a resemblance, not
so close, to the waves which run in all directions along the surface
of a pond of water from the point where a stone falls into it. These
three classes of waves, differing so immensely in magnitude and
velocity, all agree in this,--that it is the wave that travels, and
not the fluid or medium. The rapidity of the luminous wave is about
nine hundred million times that of the sound-wave; hence we may
suppose that the ether in which it moves is about as many times
rarer or lighter than air, and the retina of the eye which it
impresses as many times more delicate and sensitive than the drum of
the ear. It can hardly be unreasonable to suppose that a fluid so
rare as this luminiferous ether will readily interflow the particles
of all other matter, gaseous, liquid, or solid, and that in such
abundance that its vibrations or agitations may be propagated through
them. Yet even the rarest gases must considerably obstruct and
modify the vibratory waves, while liquids and solids, according to
their density and structural arrangement of atoms, must do it far
more. The luminiferous ether, in which all systems are immersed,
kept hereabout in an incessant quiver through its complete and
perhaps three-fold gamut of vibrations by the sun, strikes the aërial
ocean of the earth about an average of five hundred million millions
of blows per second, for each of the seven colors, or luminous notes,
not to speak of the achromatic vibrations, whose effects are other
than vision or visionary. The aërial ocean is such open-work, that
these infinitesimal billows are not much, though somewhat, broken by
it; but when they reach the terraqueous globe itself, they dash into
foam which goes whirling and eddying down into solids and liquids,
among their wild caverns of ultra-microscopic littleness, and this
foam or whirl-storm of ethereal substance is heat, if we are not
much mistaken. According to its intensity, it expands by its own mere
motion all grosser material.
The quantity of this ethereal foam, yeast, whirlwind, hubbub, or
whatever else you please to call it, which is got up or given up by
the combustion of three pounds of good bituminous coal, according to
Mr. Joule's experiments, is more than equivalent to a day's labor
of a powerful horse. With our best stationary steam-engines, at
present, we get a day's horse-power from not less than twenty-four
pounds of coal. At this rate, the whole supply of mineral coal in
the world, as it may be roughly estimated, is equivalent only to the
labor of one thousand millions of horses for fifteen hundred years.
With the average performance of our present engines, it would
support that amount of horse-power for only one thousand years. But
could we obtain the full mechanical duty of the fuel by our engines,
it would be equal to the work of a thousand millions of horses for
sixteen thousand years, or of about fifteen times as many men for
the same time. This would materially postpone the exhaustion of the
coal, at which one so naturally shudders,--to say nothing of the
saving of having to dig but one eighth as much of the mineral to
produce the same effect. Hence some of the interest that attaches to
this discovery of Mr. Joule, which has given a new impulse to the
labor of inventors in pushing the steam-engine towards perfection.
But if the whole available mechanical power, laid in store in the
coal mines, in addition to all the unimproved wind and water power,
should seem to any one insufficient to work out this world's manifest
destiny, the doctrine of the essential unity or conservation of
force is not exhausted of consolation. All the coal of which we have
spoken is but the result of the action of sun-light in past ages,
decomposing carbonic acid in the vegetative process. The combustion
of the carbon reproduces a force exactly equivalent to that of the
sun-light which was absorbed or consumed in its vegetative separation.
Supposing the whole estimated stock of coal in the world to be
consumed at once, it would cover the entire globe with a stratum of
carbonic acid about seventy-two feet deep. And if all the energy of
sun-light which this globe receives or encounters in a year were to
be devoted to its decomposition, according to Pouillet's estimate of
the strength of sunshine,--and he probably knows, if any one does,--
deducting all that would be wasted on rock or water, there would be
enough to complete the task in a year or two. A marvellous growth of
forest, that would be! But the coal is not to be burned up at once.
When we get our steam-engines in motion to the amount of two or
three thousand millions of horse-power, and are running off the coal
at the rate of one tenth of one per cent per annum, the simple and
inevitable consequence will be that the wood will be growing enough
faster to keep good the general stock of fuel. Doubtless the forests
are now limited in their growth and stunted from their ante-Saurian
stature, not so much for want of soil, moisture, or sunshine as for
want of carbonic acid in the air, to be decomposed by the foliage,
the great deposition of coal in the primitive periods having
exhausted the supply. Our present havoc of wood only changes the
locality of wood-lots, and our present consumption of coal, rapid
enough to exhaust the entire supply in about seventy-seven thousand
years, is sure to increase the aggregate cordage of the forests. By
the time we have brought our locomotive steam-cultivators to such
perfection as to plough up and pulverize the great central deserts,
we may see trees flourish where it would have been useless to plant
the seed before we had converted so much of the earth's entrails
into smoke.
There was a time, before we had harnessed the powers of Nature to
found, forge, spin, weave, print, and drudge for us generally, that
in every civilized country the strong-headed men used their
strong-handed brethren as machines. Only he could be very knowing who
owned many scribes, or he very rich who owned many hewers of wood
and drawers of water. With our prodigious development of mechanical
inventions, iron and coal, our mighty steam-driven machinery for
making machines, the time for chattelizing men, or depending mainly
on animal power of any sort for the production of wealth, has passed
by. Abrogate the golden rule, if you will, and establish the creed
of caste,--let the strongest of human races have full license to
enslave the weakest, and let it have the pick of soil and staples,--
still, if you do not abolish the ground rules of arithmetic, and the
fact that a pound of carbon costs less than a pound of corn, and must
cost less for at least a thousand years to come, chattelism of man
will cease in another generation, and the next century will not dawn
on a human slave. At present, a pound of carbon does not cost so
much as a pound of corn in any part of the United States, and in no
place visited by steam-transportation does it cost one fifth as much.
We are already able to get as much work out of a pound of carbon as
can be got from a pound of corn fed to the faithfullest slave in the
world. Mr. Joule has shown us that there is really in a pound of
carbon more than twice as much work as there is in a pound of corn.
The human corn-consuming machine comes nearer getting the whole
mechanical duty or equivalent out of his fuel than our present
steam-engine does, but the former is all he ever will be, while the
latter is an infant and growing.
We shall doubtless soon see engines that will get the work of two
slaves out of the coal that just balances one slave's food in the
scales. Our iron-boned, coal-eating slave, with the advantage of
that peculiar and almost infinitely applicable mechanical element,
the wheel, may be made to go anywhere and do any sort of work, and,
as we have seen, he will do it for one tenth of the cost of any
brute or human slave.
But will not our artificial slave be more liable to insurrection?
Everybody admits that he already accomplishes incalculable drudgery
in the huge mill, on the ocean, and on the iron highway. But almost
everybody looks upon him as a sleeping volcano, which must sooner or
later flare up into irresistible wrath and do frightful mischief.
Underwriters shake their prudent heads at him. Coroners' inquests,
sitting solemnly over his frequent desolations, find only that some
of his ways are past finding out. Can such a creature be
domesticated so as to serve profitably and comfortably on by-roads
as well as high-roads, on farms, in gardens, in kitchens, in mines,
in private workshops, in all sorts of places where steady,
uncomplaining toil is wanted? Can we ever trust him as we trust
ourselves, or our humble friends, the horse and the ox? The law of
the conservation of force, now so nearly developed, will perhaps
throw some light on this inquiry.
Boiler explosions have a sort of family resemblance to the freaks of
lightning or the thunderbolt. Indeed, so striking is the similarity,
that people have been prone to think, that, previously to an
explosion, the steam in the boiler must have become in some
inexplicable way charged with electricity like a thunder-cloud, and
that the discharge must have occasioned the catastrophe. It is
needless to say to those who understand a Leyden jar, that nothing
of the sort takes place. The friction of the watery globules, carried
along by the steam in blowing off, is found to disturb the
electrical equilibrium, as any other friction does; but the
circumstances in the case of a boiler are always so favorable to its
restoration, that an electrical thunderbolt cannot possibly be
raised there that would damage a gnat. Yet a boiler explosion may,
after all, depend on the same immediate cause as the mechanical
effect which is frequently noticed after an electrical discharge in a
thunder-storm. Let us hypothetically analyze what takes place in a
thunder-storm. For the sake of illustration, and nothing more, we
will suppose the existence, throughout all otherwise void space, of
three interflowing ethers, the atoms of each of which are, in regard
to each other, repellant, negative, or the reverse of ponderable,
and that these ethers differ in a series by vast intervals as to
size and distance of atoms, that each neither repels nor attracts
the other, that only the rarest is everywhere, and that the denser
ones, while self-repellant, have affinities, more or less, which
draw them from the interplanetary spaces towards the ponderable
masses. Let the rarest of these ethers be that whose vibrations
cause the phenomena of light,--the next denser that which, either by
vibration or translatory motion, causes the electrical phenomena,--
and the most dense of the three that which by its motions, of
whatever sort, causes the phenomena of heat. The solar impulse
propagated through the luminiferous ether towards any mass encounters
in its neighborhood the electrical and calorific ethers, and sets
them into motions which may be communicated from one to the other,
but which are communicated to ponderable matter, or result in
mechanical action, only or chiefly by the impulse of the denser or
calorific ether. When the sun shines on land and water, as we have
already said, there is a violent ethereal commotion in the
interstices of the superficial matter, which we will now suppose to
be that of the calorific ether; and by virtue of this motion,
together with whatever affinities this ether may be supposed to have
for ponderable matter, we may account for evaporation, and the
production of those vast aërial currents by which the evaporated
water is diffused. In the production of aërial currents, heat is
converted into force, and hence vapor is converted into watery
globules mechanically suspended on clouds, which, by their friction,
sweep the electrical ether into excessive condensation in the great
Leyden-jar arrangement of the sky. Whatever it may be that gives
relief to this condensation, the relief itself consists in motion,
either translatory or vibratory, of the electrical ether or ethers.
As this motion, if it be such, often takes place through gases,
liquids, and solids, without any sensible mechanical effect, and at
other times is contemporary with phenomena of intense heat, we may,
till otherwise informed, suppose, that, whenever it produces a
mechanical effect, it is by so impinging on the calorific ether as
to produce the motion of heat, which is instantly thereafter
converted into mechanical force. It is not so much the greatness of
the amount of this mechanical force which gives it its peculiar
destructiveness, as the inequality of its strain; not so much the
quantity of matter projected, as the velocity of the blow. One may
have his brains blown out by a bullet of air as well as one of lead,
if the air only blows hard enough and to one point. Whatever its
material, the edge of the thunder-axe is almost infinitely sharp,
and its blow is as destructive as it is timeless. But it is always
heat, not electrical discharge, which only sometimes causes heat,
that strikes the blow.
Now in the case of a steam-boiler, when the water, having been
reduced too low, is allowed suddenly to foam up on the overheated
crown-sheet of the furnace, there must be just that sudden or
instantaneous conversion of heat into force which may take place
when the current of the electrical discharge passes through the
gnarled fibres of an oak. The boiler and the oak are blown to shivers
in equally quick time. The only difference seems to be, that in one
case electricity stood immediately, in point of time, behind the heat,
and in the other it stood away back beyond the crocodiles, playing
its _rôle_ more genially in the growth of the monster forests whose
remains we are now digging from the bowels of the earth as coal. In
the normal action of a steam-boiler, the steam-generating surfaces
being all under water, however unequally the fire may act in
different localities, the water, by its rapid circulation, if not by
its heat-absorbing power, diffuses the heat and constantly equalizes
the strain resulting from its conversion into mechanical force. The
increase of pressure takes place gradually and evenly, and may
easily be kept far within safe limits. It is quite otherwise when
the conductivity of the boiler-plate is not aided and controlled by
the distributiveness of the water, as it is not whenever the plate
is in contact with the fire on one side without being also in contact
with the water on the other. Everybody knows that boilers explode
under such circumstances, but everybody does not know why.
A cylinder of plate-iron will withstand a gradually applied, evenly
distributed, and constant pressure, one thousandth part of which,
acting at one spot, as a blow, would rend its way through, or
establish a crack. This slight rent, giving partial relief to the
sudden but comparatively small force that causes it, would be
nothing very serious in itself,--no more so than a rent produced by
the hydraulic press,--if the whole force, equal, perhaps, to that of
a thousand wild horses imprisoned within, did not take instant
advantage of it to enlarge the breach and blow the whole structure
to fragments, or, in other words, if it did not permit nearly the
whole of the accumulated heat in the boiler to be at once converted
into mechanical motion. For example, a boiler whose ordinary working
pressure is one hundred pounds to the square inch, which may give an
aggregate on the whole surface of five millions of pounds, would not
give way, perhaps, if that pressure were gradually and evenly
increased to thirty millions. But if the water is allowed to get so
low that some part of the plate exposed to the fire is no longer
covered with it, that part will directly become far hotter than the
water or the mass of the steam,--dry steam having no more power to
carry away the excess of heat than so much air. After that, when the
water rises again, the first wave or wallop that strikes the
overheated plate absorbs the excess of heat, and its conversion into
steam of higher pressure than that already existing is so sudden
that it may be regarded as instantaneous. It is to be remembered
that for every pound of water raised one degree, or heat to that
amount absorbed in generating steam, a force of seven hundred and
seventy-two pounds is created. In this case a new or additional
force is created, which, acting in all directions from one point,
first takes effect on the line which joins that point with the
nearest opposite point in the wall of the boiler. If it is not like
smiting with the edge of a ponderous battle-axe, it is at least as
dangerous as a cannon ball shot along that line. If the local heat
so suddenly absorbed be but enough to raise ten pounds of water ten
degrees, it is equivalent to the force acquired by seventy-seven
thousand two hundred pounds falling through a foot, or of a
cannon-ball of one hundred pounds flying at the rate of more than a
mile per second. If by any miracle the boiler should stand this
shock or series of shocks, the pressure becomes equalized, and the
overheated plate having parted with its excess of heat, safety is
restored. But if cohesion is anywhere overcome by the sudden blow,
the wild horses stampede in all directions. The boiler, minus the
water and boiler-head perhaps, goes through ceiling, roof, and brick
walls, as if they were cobwebs, and, surrounded with fragments of
men and things, is seen descending like a comet through the
neighboring air.