ENERGY
ART. 51. _Energy._--In the days of Newton, and for a long time afterwards,
all energy went by the name of "Force." Thus Newton in his Laws of
Motion refers to the action of forces on stationary or moving bodies,
and shows how the motion of any body is effected by the impressed force.
(Art 13.)
As science advanced, and scientific research was carried into the fields
of heat, light, and electricity, we find that the various forces began
to be particularized, with the result that such terms as electrical
force, magnetic force, chemical force, etc., became common and familiar
terms. As gradually it became known that one particular kind of force
was the outcome of another kind, there was given to the world such terms
as the Correlation of Forces (Grove), in which he proved that whenever
one kind of force appeared as heat or light, it was at the expense of
another kind of force, as electricity.
Of later years, however, another term has crept into Philosophy, and
instead of the term Force, which is very indistinct and indefinite in
character, there appeared the term Energy, although Force and Energy are
not exactly synonymous terms. Thus electricity, heat, and light are
forms of energy, and are convertible into one another, in the same way
that the forces were convertible. Thus we get transformations of energy
in the same way that we had transformations of force, and conservation
of energy in the same way that we had conservation of force.
Even the term Energy, however, is being replaced in the present times by
something more definite and simple, and instead of the term Energy, we
shall find, in the development of this phase of natural phenomena, that
that term is being replaced by the simple idea of motion, or modes of
motion, and that all forms of energy, as light, heat, magnetism, and
electricity, and even Gravitation itself, are due to motion of some kind
or other. We will, however, lead up to this truth by looking briefly at
the term Energy, and see what it implies and embodies.
Energy, therefore, is that property which a body possesses, by which it
is capable of doing work. Thus our ideas of work give us our conception
of energy. For example, when a weight is lifted, work is done, and a
certain amount of energy is expended in the process. Further, the amount
of work done is proportionate to the weight lifted, and the height to
which the body is raised. Work is done against resistance, so that
whenever resistance is overcome, then work is the result. For example,
suppose one pound is lifted one foot high, in opposition to the force of
gravity, then work is done, and this amount of work is known as a
foot-pound.
If a body weighs ten pounds, and is lifted ten feet, the work done is
equal to ten pounds multiplied by ten feet (10 × 10 equals 100), so that
one hundred times the amount of work has been done in comparison with
the lifting of the one pound one foot high.
As all weight is essentially a gravitational measure, depending upon the
intensity of gravity at the place, then, whenever a body is raised or
lifted, the work so done is done against the gravity of the earth.
Work is also done, as Newton points out in the first and second laws,
whenever we apply force to any body, either stationary or already in
motion. The results of all observation and experiments prove, that
whenever we have two bodies upon which work is being done, the amount of
work is determined by the amount of energy transferred from one body to
the other, and that the actual amount of energy gained by one is equal
to the amount of energy lost by the other.
Energy is always found in association with matter, so that matter has
sometimes been termed the Vehicle of Energy. Wherever, therefore, we
find energy of any kind or sort, there we find matter also, as the two
are inseparably connected together. Thus, wherever we have heat, we have
matter in a particular state of motion, generally understood as
vibratory motion Wherever we have light, which is also a form of energy,
we also have matter in motion, that is the Aether, in a state of
periodic wave-motion; and wherever we have electricity, we have again
matter possibly in a state of rotatory motion, as we shall see later on.
Energy, therefore, is the power which a body possesses to do work.
ART. 52. _Conservation of Energy._--The principle of the Conservation of
Energy was first enunciated by Mayer in 1842. The principle may be
defined as follows: The total amount of all the energy, as light, heat,
electricity and magnetism, Gravitation, etc., in Nature is unchangeable;
so that, according to this law, the universe possesses a store of energy
which is unchangeable in quantity throughout all time. The energy may
pass from one form to another, yet the total amount ever remains the
same. It is almost unnecessary to say, that this is a principle which,
like the conservation of matter, is incapable of absolute proof, but its
assumption has greatly helped scientific thought and speculation from
time to time. Clerk Maxwell says (_Theory of Heat_) on this point: "The
total energy of any body is a quantity which can neither be increased
nor decreased by any mutual action of the bodies, though it may be
transformed into those forms of which energy is susceptible."
The conservation of energy is inseparably connected with the
conservation of matter (Art. 30). They cannot be divided, because, if
energy is only to be found in association with matter, then if the law
of the conservation of matter falls to the ground, the principle of the
conservation of energy falls with it. Energy, therefore, like matter,
cannot be destroyed or created by any process known to man. As there is
no process known, either in the chemical or in the physical world, by
which new matter may be created by man, so, in relation to energy of any
kind or sort, there is no process known by which man can create or even
destroy the smallest form of energy that exists. If energy appears in
any body or in any particular form, it is solely because of the loss of
energy in some other body, or in some other form.
All changes of energy, therefore, are simply changes due to the
difference in form in which the energy is manifested. At one time it
will be manifested in the form of light, then of heat, then in
mechanical motion, and so on. Joule gave us some good illustrations of
this principle of the conservation of energy. He showed us how
electricity could be changed into heat, and the heat into work. When
light, which is a form of energy, is absorbed by any opaque body, it is
found that the body which has absorbed it has become hotter. The energy
of light has not been destroyed, but as its energy cannot pass through
the opaque body, it has been employed in agitating the particles and
atoms of that body, which becomes hotter in consequence.
Thus from the principle of the conservation of energy, which is in
operation not only in our planetary world, but throughout the whole of
the solar and stellar space, and indeed throughout the whole universe,
we arrive at the conclusion that the total quantity of energy throughout
the universe is unchangeable. In the evolution and development of
worlds, and in the destruction of those worlds after long periods of
time, throughout all the varied manifestations of heat, light,
electricity, and magnetism, associated with the development and
destruction of each globe, the sum-total of the energy of the universe
remains the same. Meteors may rush into the atmosphere of planets, and
be dissolved into Aether through the friction, comets may be dissolved
into their component gases as they near the sun, water may be changed
into vapour by the heat of the summer sun, vegetation may be produced
from apparently dead matter, and then that vegetation may itself decay
and return to the dust by which it had been built up, but throughout all
these processes of birth and death, of evolution and devolution, the
sum-total of active living energy which is associated with all the
phenomena, remains unalterable and unchangeable. Such is the teaching of
the great principle of the Conservation of Energy as enunciated by Mayer
and Helmholtz.
ART. 53. _Transformation of Energy._--One of the chief characteristics
of energy is, that we can transform it, and it is chiefly of use to us
because of its capability to be transformed, but in all its
transformations, the total quantity of energy remains the same. The
transformation of energy renders it necessary to the existence of all
life, and to all physical change in the universe. Mayer showed us that
all energy in the solar system primarily derives its existence from the
sun, and that all plant life and physical life owe their continued
existence to the energy which is poured out from the sun upon the
planetary worlds. So that energy is always flowing from the sun into the
surrounding space in the form of light, heat, and electricity, the
medium of its passage being the universal Aether.
This principle of transformation teaches us, that heat may be converted
into electricity; that light may be converted into heat, or electricity
may be converted into either heat or light or both. This principle of
transformation naturally follows from the principle of the conservation
of energy; because, if energy cannot be destroyed in any way, but is
made to disappear by any process, it must reappear in some other form,
and therefore has been transformed from its original state. So that,
whenever one kind of energy disappears, then it is absolutely necessary,
according to the principle of conservation of energy, that some other
kind shall be produced. There cannot be any real loss or destruction.
That leads us to the next point regarding this principle of
transformation, which is that all transformations of energy take place
in fixed proportions. When a certain quantity of coal is burned, a
certain quantity of heat, or thermal energy as it is sometimes called,
is produced, and the quantity of heat so produced is definitely
proportionate to the quantity of coal consumed.
If a certain quantity of coal were burned in a perfect steam-engine,
that is one in which there would be no loss of heat, then also a
definite amount of mechanical work would be done, which would be
strictly proportionate to the heat generated by the consumption of the
coal. So that when coal is put into an engine, the potential energy of
the coal is transformed into kinetic energy of the steam, and that is
again transformed into actual mechanical energy of the engine itself, by
which work is done in driving or pushing or pulling the train along, and
the amount of work done is proportionate to the coal consumed.
Illustrations of transformation are common, and may be seen by any
person living in a large town. Thus at any electrical station or
electric tram terminus, these transformations of various forms of energy
are very familiar sights. We have first the transformation of the coal
in the furnace into heat. This heat converts water into steam, whose
motion is communicated by proper machinery into a dynamo, the product of
which is electricity. That electricity is then conveyed along wires, and
work is done by it, by moving trams along the connected tram system, or
it may be converted into heat in the carbon filament in the car itself,
which, if heated enough, will then produce the electric light. So that
starting from the coal, we have several transformations therefrom into
the forms of heat, light, motion, and finally mechanical energy, which
results in Work. The question arises as to what is the law of
equivalence in regard to the transformation of energy. That is, if we
have a certain amount of energy of a given sort, how much of any other
sort can be produced by it? The answer is partly to be found in a
statement made by Joule in 1843, which practically embodies what is
known as the first law of Thermo-dynamics, and is as follows: "When
equal quantities of mechanical effects are produced by any means
whatever, from purely thermal sources, or lost in purely thermal
effects, then equal quantities of heat are put out of existence or are
generated, and for every unit of heat measured by raising a pound of
water one degree F. in temperature, you have to expend 772 foot-pounds
of work." From this law we learn that heat may be used to do work, but
that a certain amount of heat is always used up in the process. It can
also be demonstrated that electric currents can do work, but to generate
the currents a certain amount of work must be done.
This equivalence and transformation prevail in all forms of energy,
whether it be mechanical energy, thermal or heat energy, or electrical
energy.
ART. 54. _Potential Energy._--Energy has been divided into two classes,
which are termed respectively Potential Energy and Kinetic Energy. We
will look at the former first.
_Potential Energy_ may be briefly defined as energy of position.
Thus if we lift a body from the ground, the energy which has been
imparted to it is energy of position, or potential energy. A glacier
high up the mountain possesses potential energy, because of its
position. By the mere fact that it is situated high up the mountain, it
has a capacity for doing work by its descent, and if that descent be
very sudden, the work done will be destructive work, as it may sweep
away all houses and villages in its sudden descent. Thus, by the mere
fact of its elevation, it possesses a power of doing work, which it has
lost when it has descended. Again, work done in winding up the spring of
a clock is stored up in the form of potential energy, and gradually runs
out in the form of motion or kinetic energy.
Potential energy is really the complementary principle of kinetic
energy. That is to say, the amount of potential energy lost by any body,
is equal to the amount of kinetic energy gained by the other body, to
which the energy has been transferred. In the case of a body falling, as
the potential energy diminishes, the kinetic energy increases, but the
total amount of the two combined always remains the same. This is well
illustrated in the case of a swinging pendulum. When a pendulum is at
the highest point of its swing, its velocity or kinetic energy is zero,
but at that point its potential energy is greatest. As it descends, the
potential energy decreases, but the kinetic energy increases. When the
pendulum is at the lowest point its energy is wholly kinetic, the
potential energy being zero at that point, while it has sufficient
kinetic energy to raise it to the highest level again. Throughout the
cycle of these operations, the sum-total of the two energies always
remains the same.
Professor Tait points out, in his _Recent Advances in Physical Science_,
that the available sources of all potential energy may be divided into
four classes--
1st. Fuel.
2nd. Food of Animals.
3rd. Water-power.
4th. Tidal Water-power.
All these are different forms of potential energy. Under the head of
fuel he includes not only wood, coal, but also all forms of matter that
may be used or burnt up by heat, or dissolved by chemical agencies. Thus
zinc and lead, which are used in batteries, are merely forms of fuel.
That potential energy resides in such things as wood and coal is a
matter of common experience. All our coal-fields are stores of energy,
which received their energy when in plant form, ages ago, from the sun,
and this energy is now being used to drive our machinery, to warm our
houses, and to give light to our homes and our cities. It has been
calculated that a pound of coal would give out 14,000 heat units, which
is equal to 11,000,000 foot-pounds of work, which is also equal to the
amount of work a horse can do in five hours. Again, all food, whether it
be the food of animals, as vegetables and plants, or of man, as bread,
meat, etc., are all forms of potential energy, or energy which is stored
up in matter. All forms of food have a certain amount of energy in them,
which is used up in the body in building up waste tissue and imparting
energy to the physical frame.
Again, all forms of water-power, whether it be in the form of the
flowing river or the tidal motion of the sea, possess a large amount of
potential energy which may be used up to do mechanical work. They also
possess kinetic energy, or energy of motion. We find illustrations of
the possession of potential energy by rivers and tides, in the fact that
by their fall from a higher to a lower level they may be made to do
mechanical work, as in the case of the turning of the water-wheel by the
fall of the water, which motion is communicated to machinery, and
various forms of work are the result. In Switzerland and America
advantage is being taken of the energy of falling water to generate
electricity, by means of which villages and towns are being supplied
with electric light at a very small cost.
ART. 55. _Kinetic Energy._--Kinetic energy may be defined as energy of
motion, and is the energy which a body possesses in consequence of its
motion. A body in motion thus possesses kinetic energy, which it must
impart to some other body before it can be brought to a state of rest.
The body may be simply an atom, as a vortex atom, but if it be in
motion, as all atoms are, then it must possess kinetic energy, which may
be transferred to another atom by collision, or by some other method. As
has already been pointed out in previous articles, kinetic and potential
energy are complementary to one another, the sum-total of the two
combined always remaining the same in any cycle of work, according to
the principle of the conservation of energy. We get a good example of
this oscillation from kinetic to potential, and _vice versâ_, in the
planetary system. When the earth is farthest from the sun, its velocity,
and consequently its kinetic energy, is at its lowest point; but there
the potential energy is at its greatest. As the earth turns round in its
orbit, however, and begins to approach the sun again, its potential
energy decreases, while its kinetic energy increases with its increased
velocity. So that by the time it has reached the nearest part of its
orbit to the sun, its velocity, and consequently its kinetic energy, is
at a maximum, while the potential energy is at a minimum. Then as the
earth passes round its perihelion, the kinetic energy is used up in
assisting the earth to overcome the attraction of the sun. Thus there is
this oscillation from kinetic to potential, and from potential to
kinetic, year in and year out, as the earth performs its cycle round its
central body the sun.
Professor Tait, in the work referred to in the previous Article, gives
examples of kinetic forms of energy under the following heads--
1st. Winds.
2nd. Currents of Water.
3rd. Hot Springs and Volcanoes.
It can be readily seen that winds are a form of energy, as we have
innumerable instances of the power and energy which they exert.
Advantage is taken of that kinetic energy by means of windmills, in
which the energy of the wind is imparted to the revolving sails, and
thence to the machinery, various forms of mechanical work being the
result, as, for example, the grinding of corn, or the pumping of water.
The pressure or energy of winds has even been calculated, the following
figures being examples--
VELOCITY IN MILES PER HOUR. FORCE IN LBS. PER SQ. FOOT
1 mile. .005 lb. per sq. foot.
5 " .123 " " "
10 " .496 " " "
15 " 1.11 " " "
20 " 1.98 " " "
30 " 4.5 " " "
40 " 7.9 " " "
50 " 12.5 " " "
In the case of currents of water, whether they are in the form of river
currents or ocean currents, as has already been pointed out in the
previous article, the question of potential energy, or energy of
position, is associated with their kinetic energy. Water is taken at a
certain elevation, and then allowed to fall to a lower level, and in its
fall from the high level to the lower level, its kinetic energy is used
to drive mill-wheels, and thus work is done, the kinetic energy of the
water being transformed into the motion of the machinery. This machinery
may be used to work a dynamo, and thus electric light may be generated,
or it may drive an electric motor which may perform all sorts of
mechanical work. The great underlying principle of either kinetic or
potential energy rests in the fact, that wherever we have energy of any
kind or sort, whether it be associated with water, wind, or Aether,
there we have the capacity to do work, the amount of work depending upon
the amount of energy that exists in the matter which is the vehicle of
energy.
In Art. 50 it has been indicated that the Aether possesses several kinds
of motions. From the sphere of light and heat, we learn that the Aether
possesses certain motions which are always exerted in a direction from
the central body, which gives rise to the light- and heat-waves. That
being so, it conclusively follows that the Aether possesses kinetic
energy, and therefore, possessing this energy, it also possesses the
power to do work. It must be remembered we are no longer dealing with a
frictionless medium, but with a gravitating medium, possessing mass and
inertia, and, that being so, wherever we have the Aether in motion,
there we have kinetic energy or the power to do work; and that work will
correspond to the particular kind of motion which is exerted on any body
by the aetherial motions, and will be equally subject to Newton's Laws
of Motion.
ART. 56. _Energy and Motion._--An advance, however, as to the meaning of
the term Energy has been made within recent years, which brings it more
into harmony with that simplicity of conception, and accordance with
experience which are the very foundation of all philosophy. Instead of
the term Energy, there is now being used another term to denote the
forces which form the life of the universe, and that term is the word
"Motion."
Professor Poynting says: "All energy is energy of motion" (_British
Association Report_, 1899).
Thus motion is the fundamental principle of all phenomena. If we analyze
all forms of energy with which we are familiar, we shall soon find that
they are only changes of one form of motion into another. Thus we shall
see that heat is a mode of motion, as has been proved by Tyndall, that
light is another mode of motion, and that electricity is also a mode of
motion. I need hardly point out that this advance in our conception of
energy is strictly in accord with the Rules of Philosophy. First, it is
simple in conception. When we say that a body possesses energy, whether
that energy be potential energy or kinetic energy, it does not convey to
the mind some definite concrete fact, as does the statement that a body
possesses motion. Every one, whether familiar with scientific teaching
or not, understands and is familiar with the word Motion, as it is a
common phenomenon of everyday life and experience. As Energy was simpler
in conception than Newton's term Force, so Motion is simpler in
conception than the rather vague and indefinite term Energy; therefore
when we say that all energy is energy of motion of some kind or sort, we
state that which is philosophically correct.
It is also in accord with the second Rule of Philosophy, in that it is
strictly in harmony with experience and observation. Look where we will,
or at what we will, there we find motion of some kind or other, whether
it be among the innumerable stars, or in our own solar system, or any
phenomena on the earth, or even among the world of atoms in their minute
and atomic systems. Such a thing as absolute rest, or stagnation, is
unknown in the universe. Wherever there is matter, there we find motion
of some kind or other. It may be vibratory motion as heat, or wave
motion as light, or rotatory motion as electricity, but motion of some
sort is inseparably connected with all matter. So that when we say that
all energy of the universe is the energy of motion, and motion only, we
state that which according to the second Rule of Philosophy is
absolutely correct.
Further, I wish to premise that by the use of the term modes of motion,
in lieu of energy, the third Rule of Philosophy will be fulfilled. For
if all phenomena of the universe, whether it be heat, light,
electricity, be due to different modes of motion, then Gravitation
should be explained from the physical standpoint by some kind of
aetherial motion also. This I can safely premise will be done, and in
the later chapters of this work, Gravitation will be shown to be due to
the motions of the aetherial medium which floods all space. By so doing,
all the Rules of Philosophy will be fully satisfied, and Gravitation
will then be brought into line with all the other forms of motion, as
heat, light, electricity, and magnetism, which are in themselves modes
of motion, as will be shown in subsequent articles.
ART. 57. _Conservation of Motion._--If it be true that all energy is the
energy of motion, then the principle of the conservation of energy ought
also to apply to all the modes of motion, and in its place we should
then have the principle of the conservation of the various forms of
motion. This defined would be, that the total amount of all motion in
the universe, as heat and light, electricity, magnetism, and Gravitation
also, if that be due to the motion of the Aether, is unalterable and
unchangeable.
There may be changes from one form of motion to another, from heat to
light, and light back to heat; heat into electricity, and electricity
into light or heat; from Gravitation into heat or into light, or even
into electricity; but the sum-total of the whole remains the same.
Again, as the principle of the conservation of energy is inseparably
connected with the conservation of matter, so the principle of the
conservation of all the modes of motion is also inseparably connected
with the conservation of matter. They cannot be divided, so that
wherever we get matter of any kind or sort, there we get motion of some
kind, either in the form of heat, light, or electricity, or those
aetherial motions which produce those phenomena associated with
Gravitation.
As matter cannot be destroyed by any known process to man, so motion
cannot be destroyed either. On the vortex atom theory of matter, this
principle of the conservation of any mode of motion is perfectly
intelligible, especially if added to that theory we have Dr. Larmor's
electron theory as the basis of the vortex atom. An atom in its ultimate
state is nothing more or less than Aether in rotation, and as Aether is
matter, we see that on the assumption of this atomic basis, we have even
in the atomic world an illustration of this conservation of matter and
motion, as in such an atom we have nothing but matter (_i. e._ Aether)
and motion. Carrying the idea upwards in the atomic scale, if atoms of
hydrogen or oxygen are multiples of these vortex atoms, then again we
have nothing in all the elements, or combination of the elements, but
matter and motion. Again, as all planets and satellites, suns and stars,
are but agglomerations of elements, we have still the same two classes
of things, matter and motion, and so from the most infinitesimal atom in
existence, up to the most ponderous star that exists in the universe, we
have running through them all the principle of the conservation of
motion, which is to matter the source of all its activities, energies,
and powers. Motion, therefore, might almost be said to be eternal. We
have heard from time to time of the term perpetual motion. Philosophers
have from time to time endeavoured to discover some application of this
perpetual motion, but all efforts in this direction up to the present
have proved futile. In one sense there is no such thing as perpetual
motion. In another sense, that is from the standpoint of the
conservation of all modes of motion, as motion cannot be destroyed, it
must therefore be perpetual.
It is an absolute impossibility to obtain motion except from some
antecedent energy, which is itself a form of motion. It would require
the distinctive fiat of an Almighty Creator to produce motion from
nothing, and I question whether such a result is obtainable, as I hold
that if the Creator, at any time in the history of the universe, set any
substance in motion, the source from which that motion was derived, was
His own Divine Energy, and in that sense the physical motion was not
produced from nothing. Such an assumption is altogether opposed to all
philosophical reasoning and experience. I hope to deal with the question
either in the last chapter of this book, or in another work.
ART. 58. _Transformation of Motion._--Again, if energy be the energy of
motion, and the principle of the transformations of energy holds good,
then it is equally true that all modes of motion are also transformable.
Thus heat is a mode of motion, being due to the vibration of the atoms
which go to make up any body. Light is also a mode of motion, being due,
as far as solar light is concerned, to the periodic wave motion of the
Aether. While electricity, as we shall see later on, is also due to some
form of rotatory motion. It has already been shown (Art. 54) that light
can be converted into heat, so that the periodic wave motion of light
can be transformed into the vibratory motion of heat.
Heat can also be converted into electricity, and if electricity be
rotatory motion, then the vibratory motion of heat can be transformed
into the rotatory motion of electricity. Again, as electricity can be
converted into light, the rotatory motion of electricity can thus be
transformed into the periodic wave motion of light. Thus through all the
forms of motion with which we are familiar, we find this principle of
transformation holds good, so that each form of motion may be directly
or indirectly transformed into any one of the other kinds. Whenever,
therefore, one kind of motion disappears, it is absolutely necessary,
according to the principle of the conservation of motion, that some
other kind shall be produced. There cannot be any real loss or
destruction of the motion. It may be transformed, but not lost. By the
use of proper apparatus, therefore, any form of motion with which we are
familiar may be converted into another form, and in the process not the
least quantity of any form of motion is lost. Heat may be changed into
light, and light into heat; electricity into light, and light into
electricity; heat into electricity, and electricity into heat. Indeed,
starting from any one form, any of the other modes of motion may be
produced, either directly or indirectly, and mechanical effects or work
may be produced by each and all. Then, again, the order can be reversed,
as by doing work which is simply applied motion, any of the other modes
of motion can be produced. Thus heat can be produced by friction, and if
the friction which is the outcome of muscular energy be continued long
enough, a light will be the result, in the form of fire. When certain
forms of work are done, as the turning of the handle of an electrical
machine, frictional electricity will be produced. So that not only are
all the modes of motion convertible into work, but work itself can be
transformed into the modes of motion known as heat, light, electricity,
and magnetism.
Now, if Gravitation be due to motion of the Aether, and if it is true
that all modes of motion are convertible, then the application of this
principle should also hold good in relation to Gravitation. It has been
demonstrated by Joule and others that Gravitation can be converted into
heat, light, and electricity. It can be converted first into heat. Joule
made a number of experiments to ascertain what quantity of heat is
produced by falling bodies, that is bodies under the influence of
Gravitation. From experiments he has calculated that if one lb. of water
falls through a space of 772 feet, it would raise the temperature of
the water one degree Fahrenheit--that is, the water after its fall will
be one degree hotter than when it started to fall. Here, then, we have
the exact equivalence of a certain amount of gravitational motion
expressed in terms of heat. So that, whenever motion of a falling body
produced by gravity is arrested, heat is generated, and as heat is a
mode of motion, it follows that the motion of Gravitation has been
converted into the motion of heat. Again, the motion of gravity may be
converted into that of light. This may be demonstrated as follows: Lord
Kelvin has suggested that the light and heat of the sun are maintained
by the falling into the sun of meteorites. Now the cause of the falling
of these meteorites into the sun is the Attraction of Gravitation, and
therefore if the falling of these meteorites produces light and heat, it
necessarily follows that the motion of Gravitation, whatever that may be
due to, is converted into the motion known as light and heat. Thus it
can be seen that Gravitation, looked at from the standpoint of a mode of
motion, is itself conformable to the principle of the transformation of
motion, and this is an indirect argument in favour of the fact that
Gravitation is itself due to certain motions of the universal Aether.
ART. 59. _Motion and Work._--In Art. 52 we have seen that energy is the
power which a body possesses to do work, the amount of work which a body
can perform being regulated by the amount of energy which such a body
possesses. In Art. 57 we have further seen that all energy is the energy
of motion, and that wherever we have energy of any kind or sort, whether
it be in the form of light, heat, or electricity, there we have motion
of some kind or other. That being so, we arrive at the conclusion, that
wherever in the universe we have motion of any kind or sort, whether it
be the motion of Aether, or wind, or water, there we have the power of
doing work, and the work so done will be proportionate to the motion
which the medium possesses. The amount of work that air in motion can do
has been measured, as we have already seen (Art. 55) that air which
moves at the rate of 30 miles per hour exerts a force of 4-1/2 lb. per
square foot.
The amount of work that water in motion can do has also been measured.
The carrying and erosive powers of a river depend on the rapidity of its
currents. It has been calculated that a velocity of three inches per
second will transport fine clay; eight inches per second coarse sand;
while three feet per second will transport stones as large as eggs.
If, therefore, air moving at the rate of 30 miles an hour can exert a
force of 4-1/2 lb. per square foot, what must be the force or pressure
of aetherial motion, as light-waves for example, which move with a
velocity of 186,000 miles per second? The amount of work which such an
aetherial motion can perform has actually been measured by Professor
Lebedew of Moscow, and will be dealt with in the chapter on "Light, a
Mode of Motion," when the application of the work done on a body, as a
planet for example, will also be considered. Work, therefore, can always
be done by motion against resistance. This is a fundamental principle in
the sphere of dynamics, which is incontrovertible, as all experience,
observation, and experiment teach us, that wherever we get motion of any
kind or sort, there we have the capacity or power to do work. The work
done may be either in the form of pushing a body along, or pulling a
body towards a centre. All experience and observation teach us that no
body moves (whether it be an atom, or moon, or planet, or sun, or star),
unless some other body or medium, which is in direct contact with the
moving body, exercises some pressure or pull upon the moving body. The
action is purely and simply a mechanical one. So that if this be true,
then the earth and the planets, the sun and stars, comets and meteors,
are moved through space solely because they are being pushed by some
medium, or pulled to the centre by the motions of the same medium. If
this can be proved to be true, then, as can be readily seen, our
philosophy will then be made to agree with our experience, and the
second Rule of Philosophy fully satisfied. As has already been pointed
out, there is no such thing as action at a distance, therefore the Law
of Gravitation demands a medium for its operation, production, and
continuity. Newton distinctly points this out in his Letters to Bentley,
where he says: "That one body should act upon another through empty
space without the mediation of anything else, by and through which their
action and pressure may be conveyed from one to another, is to me so
great an absurdity that I believe no man who has in philosophical
matters a faculty for thinking can ever fall into it." It has already
been pointed out (Art. 42), that the only medium which is universal is
the Aether medium, and we have therefore to look to the motions and
properties of that medium for the solution of the problem as to the
physical cause of Gravitation. That such a medium has motions which are
as regular as the tides of the sea, or the trade winds of the
atmosphere, will be proved later on, when it will be found that
Gravitation, with all that that law implies, is due, as Newton and
Challis suggested, to the pressure, properties, and motions of the
aetherial medium, which is as universal as Gravitation itself. This
being so, it is essential that we should set ourselves to find out from
the analogies of Nature, what are those properties and motions of the
Aether which give rise to the universal Law of Gravitation. This I
propose doing by a consideration of three different modes of
motion--viz. Heat, a mode of motion; Light, a mode of motion; and
Electricity, a mode of motion. I venture to premise, from a careful
consideration of these three truths, that we shall be able logically and
philosophically to arrive at the simple, yet grand truth which reveals
the physical source of all motion of the universe.