Principles of Energetics. 355 
perty by experience,” it also “may admit of explanation by a 
complete theory of molecular forces?” Is it not therefore self- 
contradictory to attribute elasticity to one sort of matter, and 
justify its denial to another, on grounds which would equally 
apply to the quality by which this other sort of matter is distin- 
guished from the former? And is not a theory fallacious which, 
if it attempts to explain relative elasticity or relative hardness, 
must do so by means of hypothetical and inconceivable, abso- 
lutely elastic, and absolutely hard entities ? 
24. But further, examining these fundamental facts by the 
results of the analysis of the qualities of matter, it will be seen 
that it is attempted to found a physical theory on the hypothesis 
of a physical matter acting on a mathematical matter. An elastic 
matter may be physically conceivable ; but the interaction of such 
a matter and bodies without any physical quality, but mere 
abstractions of the metaphysical qualities deduceable from the 
respective conditions of occupying and being contained in space, 
cannot but be experimentally inconceivable. 
25. Consider therefore, thirdly, the experimental conceptions 
to which these “hypothetical facts” are opposed; and (1) the 
conception of matter. 
The conception of an absolute, or uniform, and universal elastic 
sether is opposed to the conception now formed of such similar 
entities as the old electric fluids, &c.; namely, that electricity is 
not an entity, but the expression of a certain physical relation 
between bodies, the electric state being kept up by, and entirely 
dependent upon, the bodies among which the electric body at 
any time is, or may be brought. Hence it should seem that if a 
theory requires an elastic ether, its elasticity must be conceived 
as relative or determined by the masses and distances of bodies, 
and hence evidently elasticity be conceived as “une des propriétés 
générales de la matiére* ”’ 
And the notion of absolutely existing spherical atoms of dif- 
ferent magnitudes not only begs as many separate creations of 
atoms as our fancy may suggest differences in their size, but is 
opposed to the conception of the transmutation of matter, general- 
ized from the fact that we have in physics at least no creations, 
but perpetual changes dependent upon the ever-varying relations 
of bodies. 
_ 26. But (2) the idea of motions arising from the action of an 
elastic fluid on an inelastic absolutely hard and smooth body is 
opposed to all experimental conceptions of the interaction of the 
parts of matter. For not only do we seem to be led by experi- 
ment to a conception of the continuity of every part of matter by 
the cohesion of other bodies, so that it should seem to be impos- 
* Lamé, quoted in Part I. of a ams Phil. Mag. April, p. 275. 
2 
