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by this denial of ether distinct from matter, the doctrine ot 
Conservation, in its very basis, would be made not only 
doubtful and unproved, but even impossible. 
Fourthly, the doctrine, to meet the facts, requires the exist- 
ence of a law of repulsion, in some ethereal medium, depending 
on the distance, and varying far more rapidly than gravity, and 
also an intermediate law of cohesive attraction, which may be 
that of matter on ether. Now, Mr. Spencer affirms gravitation 
to be a necessary result of the laws of space. If so, either a 
repulsion, or any attraction varying by a higher law than the 
inverse square, is impossible in the nature of things. For no 
atoms can attract and repel each other at the same moment, or 
attract by two different incompatible laws at the same time. How 
can statements so plainly contradicted by all the facts of science 
be the basis of new and improved philosophy ? 
Again, the doctrine implies that every atom is a centre of 
force, varying ever in its amount, but acting every moment on 
all other atoms. Yet the paper asserts that matter may impart 
motion without any force, by its movement alone. Now this 
is a double contradiction of the doctrine. For, first, it supposes 
that a moving body can be without any force, which sets aside 
the Newtonian law, and also every other that satisfies the condi- 
tions of the problem. And next, it introduces a new law of 
force, depending on the speed, not the distance, which is equally 
fatal to the truth of the theory he undertakes to prove. 
But I must draw these remarks to a close. The Conservation 
of Motion, as a physical theory and hypothesis, does not mean 
that the total motion of the universe is constant, for it is ever 
varying, and must ever vary, by any probable laws of force. It 
does not mean that force is motion, or motion force, for one is 
the cause, the other its effect. It does not mean that the sum 
of the forces is constant, for they vary separately as each distance 
varies, and collectively, as the whole system contracts or 
expands. It does not mean that their sum is constant, for 
under many conceivable alternatives both the forces and the 
motions may increase together. It does not mean that the 
total of all force, at all conceivable distances, is a constant, 
measurable quantity, for by the assumed laws this total, in each 
pair of atoms, and much more in their collective sum, is infinite 
and immeasurable. It means, really, thStt the true constitution 
of matter and ether, the medium of light and electricity, is that 
of centres of force, which repel more and more, and never 
touch, and not that of finite, solid atoms, which being impene- 
trable, not repulsive, would suddenly stop in collision and 
destroy the opposite motions. As a key to the various modes 
