:8c) 1 .] 
187 
[Dolbear. 
Now the kinetic theory of gases explains the pressure of a gas 
as being due to the impact of the molecules upon the surface of 
the containing vessel. The source of the free path motion that 
is arrested by the impact, is the vibratory motion that constitutes 
the heat of the molecules, and the energy is therefore propor- 
tional to the absolute temperature. At absolute zero there would 
be no free path, because there is no heat to spend to produce it. 
It is, however, important here to bear in mind that free path 
motion is not heat, in either small or large bodies, though in most 
books on thermo-dynamics it is assumed as being heat, and that 
the heat of a gas is in two parts, an external or free path and an 
internal or true vibration, the total heat being the sum of the two. 
That this cannot be so will be seen from the following considera- 
tions : — 
Assume a litre of gas at any temperature to be removed to an 
empty space, say a million miles from the earth, and suddenly set 
free. The molecules will now scatter in direction and with ve- 
locity determined by the last molecular impacts, and being in a 
frictionless medium their velocity will be uniform, so after an in- 
terval of say a day, their freepath energy will be what it was at the 
outset, but each individual molecule will now continuously lose its 
temperature by direct radiation, and might arrive in that way to 
absolute zero, — in which case we should have the anomalous result 
of a mass of gas at absolute zero possessing heat ! ! which is absurd. 
It follows therefore that heat is a true molecular or atomic vibra- 
tion as distinguished from any other kind of motion and when a 
hot body loses energy by radiation it is because it has handed it 
over to the ether. 
We have now got an atom or a molecule vibrating in harmonic 
rates and reacting upon the ether so as to set up waves in it. 
Sir Wm. Thomson and others have shown us that these par- 
ticles are in the neighborhood of the one-fifty-millionth of an inch 
in diameter, and one is bound to picture to himself in some kind 
of a way what these particles would look like if they could be 
seen. The theory of atoms as hard-round somethings, endowed 
with specific properties such as elasticity, attraction, etc., breaks 
down as soon as one attempts to derive phenomena from such 
hypothesis, for the whole of physics to-day, so far as it has 
any bearing upon the question, seems to show that all phenomena, 
even the properties of the elements themselves, are due to the 
