1904 - 5 .] Mr J. Fraser on Electricity based on Babble Atom. 691 
potential.” The same is true of the surface of contact of a liquid 
with a solid, and also, hut in a much less degree, of two dissimilar 
solids. This fact will be put to its proper use, later on, when we 
come to consider current electricity. 
12. By the kinetic theory of gases the molecules of all perfect 
gases at the same temperature and pressure occupy equal spaces ; 
hut the theory takes no account of the actual sizes of the 
molecules themselves, as their sizes are considered to he infini- 
tesimal compared with the space through which they move. 
The theory is that they all have the same average free path. 
If their sizes were doubled, say, it would, no doubt, shorten their 
free paths to some small extent, hut this would immediately give 
rise to an increase in the pressure. By an increase in their sizes 
there would he an increase in their electricity, but then the 
increase of electricity would he neutralised both by their heat and 
elastic absorption (see par. 9), and the state of equilibrium in the 
medium would be undisturbed. But now, suppose we had a 
means of practically increasing their sizes without at the same 
time increasing their heat vibrations, or lengthening their free 
paths ; it will be immediately apparent that in that case the state 
of equilibrium in the medium would be instantly upset. There 
would be a greater radiation of electricity from the locality 
occupied by the enlarged molecules than from the surrounding 
parts, because there was not a sufficiency of vibratory motion to 
convert the surplus electricity to heat or appearing in the 
phenomenon of elastic absorption. Or, again, if we had a means 
of decreasing their sizes without taking away their heat-motion, 
there would be less radiation of electricity from the locality 
occupied by the collapsed molecules than from the surrounding 
parts, because a greater quantity of it would be converted into 
heat or elastic absorption than when in the neutral state. 
I will now proceed to show how the foregoing principles can 
be applied to the explanation of electrical phenomena. 
13. Electricity as it is Known. 
We have hitherto been considering electricity in its neutral 
state, but we will now consider it in its active or phenomenal 
state. In the former state all bodies are electrified alike, but 
