192 Atomic Matter and Luminiferous Ether. (April, 
by weight, the force called gravity must bear its part, and, 
hence, molecules may also be of a definite weight. To this 
extent there appear to be no analogical or inferential grounds 
for objecting to this definition of molecules. 
The theoretic formule for the velocity of the propagation of 
soundshow the velocities to be the same for each gas whatever 
be the pressure supported by it; and Regnault, by experiments 
on the large scale with pressures varying in the proportion of 
1 to 5, has verified this law. This law is of general application 
to all vibrations in elastic media; hence, if light be propagated 
with an ascertained velocity in air, at the earth’s surface, it 
should pass with the same velocity when air is indefinitely — 
attenuated. Astronomers do find that light passes through 
our atmosphere, and through stellar space with the same 
velocity ; and so far, therefore, as the sun beam is concerned, 
this space may be filled with attenuated air, instead of the 
hypothetic ether, if the air be elastic. 
The preceding remarks have incidentally illustrated the 
axiom that all force is motion, and different forces (gravity 
included) are different modes of motion; but passive 
existence, and consequently passive qualities, ready to yield 
more or less to motion of some kind, appear also to be 
necessary and axiomatic attributes of matter. We cannot 
make lace without mechanism. The machine possesses 
various passive qualities; amongst them is the capacity 
under certain conditions of making lace by the expenditure 
of energy in the form of mechanical, as distinguished from 
molecular, motion. Various machines differ in their capacity 
of transforming an identical energy, and producing from it 
various results. Whilst different chemical compounds may be 
compared to different machines, all constructed out of a few 
materials, and still fewer mechanical elements variously 
grouped, all the different natural forces, 7z.e. vibrations of all 
kinds and forms, must be conveyed by one and the same 
quality, and that most probably a passive quality, common 
to all matter. 
Continuous atomic matter appears to possess this quality 
to perfection. The waves of the sea are in number 
complicated beyond computation, and cross each in all 
possible directions. ‘They descend below the surface, and in 
a definite zone we perceive the substance of the sea must be 
in intestinal motion correlated to the visible motion of its 
surface. The waves of a lake of gas (and those of 
a large mass of carbonic acid gas, just rendered 
visible by suspended carbonate of ammonia, are mentally 
reproduced as these lines are written) are at least as 
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