66 
INEPT, 
| NOVEMBER 19, 1896 
interest that was aroused by the discoveries in all the fields of 
physical science—in heat, electricity, magnetism and chemistry 
—by Faraday, Joule, Helmholtz and others, compelled a change 
of conceptions ; for it was noticed that each special kind of 
phenomena was preceded by some other definite and known 
kind ; as, for instance, that chemical action preceded electrical 
currents, that mechanical or electrical activity resulted from 
changing magnetism, and soon. As each kind of action was 
believed to be due to a special force, there were invented such | 
terms as mechanical force, electrical force, magnetic, chemical 
and vital forces, and these were discovered to be convertible into 
one another, and the ‘‘ doctrine of the correlation of the physical 
forces” became a common expression in philosophies of all 
sorts. By ‘‘convertible into one another” was meant that, 
whenever any given force appeared, it was at the expense of 
some other force ; thus, in a battery, chemical force was changed 
into electrical force ; in a magnet, electrical force was changed 
into magnetic force, and soon. The idea here was the /vams- 
formation of forces, and forces were not so clearly defined that 
one could have a mechanical idea of just what had happened. 
That part of the philosophy was no clearer than that of the im- 
ponderables which had largely dropped out of mind. The 
terminology represented an advance in knowledge, but was 
lacking in lucidity, for no one knew what a force of any kind 
was. 
The first to discover this and to repudiate it were the physio- 
logists, who early announced their disbelief in a vital force, and 
their belief that all physiological activities were of purely 
physical and chemical origin, and that there was no need to 
assume any such thing as a vital force. Then came the dis- 
covery that chemical force, or affinity, had only an adventitious 
existence, and that, at absolute zero, there was no such activity. 
The discovery of, or rather the appreciation of, what is implied 
by the term adsolute zero, and especially of the nature of heat 
itself, as expressed in the statement that heat is a mode of 
motion, dismissed another of the, so-called forces as being a 
metaphysical agency having no real existence, though standing 
for phenomena needing further attention and explanation—and 
by explanation is meant ¢he presentation of the mechanical ante- 
cedents for a phenomenon, tn so complete a way that no supple- 
mentary or unknown factors are necessary. The train moves 
because the engine pulls it ; the engine pulls because the steam 
pushes it. There is no more necessity for assuming a steam 
force between the steam and the engine, than for assuming an 
engine force between the engine and the train. All the pro- 
cesses are mechanical, and have to do only with ordinary matter 
and its conditions, from the coal pile to the moving freight, 
though there are many transformations of the forms of motion 
and of energy between the two extremes. 
During the past thirty years, there has come into common 
use another term, unknown in any technical sense before that 
time, namely, evergy. What was once called the conservation 
of force is now called the conservation of energy, and we now 
often hear of forms of energy. Thus, heat is said to bea form of 
energy, and the forms of energy are convertible into one another, 
as the so-called forces were formerly supposed to be transform- 
able into one another. We are asked to consider gravitative 
energy, heat energy, mechanical energy, chemical energy, elec- 
trical energy. When we inquire what is meant by energy, we 
are informed that it means ability to do work,-and that work is 
measurable as a pressure into a distance, and is specified as foot- 
pounds. A mass of matter moves because energy has been 
spent upon it and has acquired energy equal to the work done 
on it, and this is believed to hold true, no matter what the kind 
of energy was that moved it. 
What a given amount of energy will do depends only upon its 
Jorm ; that is, the kind of motion that embodies it. The energy | 
Spent upon a stone thrown into the air, giving it translatory 
motion, would, if spent upon a tuning-fork, make it sound, but 
not move from its place ; while if spent upon a top, would 
enable the latter to stand upon its point as easily as a person 
stands on his two feet, and to do other surprising things, which 
otherwise it could not do. One can, without difficulty, form a 
mechanical conception of the whole series without assuming 
imponderables, or fluids or forces. Mechanical motion only, by 
pressure, has been transferred in certain directions at certain 
vates. Suppose now that some one should suddenly come upon 
a spinning-top while it was standing upon its point, and, as its 
motion might not be visible, should cautiously touch it. It 
would bound away with surprising promptness, and, if he were 
NO. 1412, VOL. 55] 
not instructed in the mechanical principles involved, he might 
fairly well draw the conclusion that it was actuated by other 
than simple mechanical principles, and, for that reason, it would 
be difficult to persuade him that there was nothing essentially 
different in the body that appeared and acted thus, than in a 
stone thrown into the air; nevertheless, that statement would 
be the simple truth. 
All of our experience, without a single exception, enforces 
the proposition that no body moves in any direction, or in any 
way, except when some other body 27 contact with it presses upon 
it. The action is direct. In a letter from Newton to his friend 
Bentley, he says: ‘‘ That one body should act upon another 
through empty space, without the meditation of anything else 
by and through which their action and pressure may be con- 
veyed from one to another, is to me so great an absurdity that I 
believe no man who has in philosophical matters a competent 
faculty of thinking can ever fall into it.” 
For mathematical purposes, it has sometimes been convenient 
to treat a problem as if one body could act upon another without 
any physical meaning between them; but such conception has 
no degree of rationality, and I know of no one who believes in 
that asa fact. If this be granted, then our philosophy agrees 
with our experience, and every body moves because it is pushed, 
and the mechanical antecedent of every kind of phenomenon is 
to be looked for in some adjacent body possessing energy—that 
is, the ability to push or produce pressure. 
It must not be forgotten that energy is not a simple factor, 
but is always a product of two factors: a mass with a velocity, 
a mass with a temperature, a quantity of electricity into a pres- 
sure, and so on. One may sometimes meet the statement that 
matter and energy are the two realities ; both are spoken of as 
entities. It is much more philosophical to speak of matter and 
motion, for in the absence of motion there is no energy, and 
the energy varies with the amount of motion ; and furthermore, 
to understand any manifestation of energy one must inquire 
what kind of motion is involved. It.is now too late to stop 
with energy as a final factor in any phenomenon ; and the form 
of motion which embodies the energy is the factor that deter- 
mines waz happens, as distinguished from how mzch happens. 
Here, then, are to be found the distinctions which have hereto- 
fore been called forces ; here is embodied the proof that direct 
pressure of one body upon another is what causes the latter to 
move, and that the direction of movement depends on the point 
of application, with reference to the centre of mass. 
ACTION AT A DISTANCE. 
Let us now look at the other term in the product we call 
energy, namely, the substance moving, sometimes called matter 
or mass. It has been mentioned that the idea of a medium 
filling space was present with Newton, but his gravitation 
problem did not require that he should consider other factors 
than masses and distances. The law of gravitation as considered 
by him was: Every particle of matter attracts every other particle 
“of matter with a stress which is proportional to the product of 
their masses, and inversely to the squares of the distance between 
them. Here we are concerned only with the statement that 
every particle of matter attracts every other particle of matter. 
Everything then that possesses gravitative attraction is matter 
in the sense in which that term is used in this law. If there be 
any other substance in the universe that is not thus subject to 
gravitation, then it is improper to call it matter. 
We are now assured that there is something else in the universe . 
which has no gravitative property at all, namely, the ether. It 
was first imagined in order to account for the phenomena of 
light, which was observed to take about eight minutes to come 
from the sun to the earth. Then Young applied the wave theory 
to the explanation of polarisation and other phenomena ; and, 
in 1851, Foucault proved experimentally that the velocity of 
light was less in water than in air, as it should be if the wave 
theory be true, and this has been considered a crucial experiment 
which took away the last hope for the corpuscular theory and 
demonstrated the existence of the ether asa space-filling medium 
capable of transmitting light waves known to have a velocity of 
186,300 miles per second. It was called the luminiferous ether, 
to distinguish it from other ethers which had also been imagined, 
such as electric ether for electric phenomena, magnetic ether for 
magnetic phenomena, and so on—as many ethers as there were 
different kinds of phenomena to be explained. 
It was Faraday who put a stop to the invention of ethers, by 
suggesting that the so-called luminiferous ether might be the one 
