187 
hundredw eight lost because the ton of which it is part is not 
put into motion ? The error lies in that begging of the 
whole question which makes work to consist of motion ; but 
that utilitarian idea will hardly be mistaken by physicists for 
the work which science takes into account under the calcula- 
tions of action and reaction. 
Force, then, operating physically at a constant distance, is 
never lost, as those who teach the conservation of energy '' 
assert that it can be ; nor is the immunity from loss under 
those particular circumstances, by any means “ conservation 
of force,” — a doctrine which requires the total amount of 
force existing in the universe, under some one of many 
alleged forms, to be never greater, nor less, at one time than 
at another; whereas we know, in the case of gravity for 
example, that by the law of distance the downward force of a 
ton's weight at the earth's surface would become gradually 
lessened as its distance from the earth was made greater. 
The same also with other forces of matter ; experience teaches 
that one and the same quantity of electricity varies very 
palpably in absolute force under unchanging relations of time 
and place, according as it may be acting alone or in concert 
with other similar quantities. 
So far as force is concerned, it is plain, then, that it cannot 
be conserved, though not for the reason alleged by the 
partisans of conservation. Those philosophers, believing in 
the loss of force, and requiring something that will remain 
always the same in amount, give force a new name ; and, 
calling it energy, admit under that appellation only such 
dynamic, or unbalanced forces as are capable of producing 
motion ; but the doctrine is not made by the limitation any 
the more consistent with truth. Of the distinction thus 
introduced, I reason as follows : All force, whether under its 
proper name, or that of energy, tends to produce motion, and 
force is either in a static or a dynamic condition. In the 
static condition force, tending to produce motion, is counter- 
balanced, though still existing, but being counter-balanced, 
produces no motion. In the dynamic condition, force actually 
produces motion, and ends in becoming static by establishing 
an equivalence of reaction. 
Now, inasmuch as motions end with the expiration of the 
dynamic condition on which motion depends, energy, which is 
only a new name for that condition, cannot be a continuation 
or phase of motion. And to the above there is to be added 
this positive denial of the doctrine of conservation : Motion 
cannot be a phase of force, for if it were so, force should 
invariably become greater when motion ceased, whereas it 
