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sometimes becomes less, as we always find when the motion 
increases the distance at which the force is acting. Again : 
Motion is alleged to change into heat, but to produce heat is 
to establish dynamic force, whereas to produce motion, which 
is alleged to be correlative to heat, is to change dynamic 
into static force. Besides which the allegation violates an axiom 
by imputing to a single cause two effects, each equal to itself ; 
for it imputes to motion heat on the one hand equal to the 
motion, and on the other, physical reaction equal to the 
energy which has caused the motion. And, finally, we may 
reason thus, on analogy : If electrical force be distinct from 
electrical matter, then it is not likely that heat is a force, while 
caloric is only an imaginary material ; in denial of the long 
and almost universally prevailing belief that heat is a force 
consequent upon the operation of a material caloric. 
Let me close this argument in disproof of the alleged 
constancy of energy or force under any form whatever, 
by citing a fact which has now become very common- 
place ; and must either be explained away in some manner 
which no one has been able to suggest during thirty years, 
or be received as settling the question for ever. Adopting the 
language in use, the energy accumulated in a horizontal disc 
weighing one pound raised one foot above any resting-place 
paralled with it would be a foot-pound. If, instead of the 
gravitation of the disc, there were substituted an equal 
downward pressure by electrical charge, the potential energy , as 
some call it, would still be one foot-pound. Suppose now 
half the electrical charge to be withdrawn; this, on the con- 
servation theory, should reduce the downward pressure to one 
half of a foot-pound , but practically it makes the foot-pound 
only a quarter of a foot-pound; where then is the other 
quarter of a foot-pound if “ energy can never be lost ” ? 
With difficulties insuperable as these opposing the doctrine 
of (C conservation,” and with a problematical immateriality of 
electricity and heat for its foundation ; we may well think out 
of place the flippancy with which the general views of heat, 
while they are acknowledged to have been long “ believed in, 
written about, and taught all over the world,” have lately 
been ridiculed, as “ the pleasant fiction called Caloric ; ” by 
writers, who, seemingly without a misgiving, can thus com- 
plain that their own mechanical and utilitarian speculations 
are not adopted by physicists as infallible guides : “ no one 
who knows the present state of science can ignore the fact 
that many of its most certain truths are still misunderstood, 
and their very opposites often taught, even by men who by 
their position or their notoriety are supposed by the public to 
