686 Proceedings of Royal Society of Edinburgh. [sess. 
must be noted that the electricity is proportional to surface area 
irrespective of its density or close-grainedness, for though the 
particles of the densest kind of atoms have each of them less 
electricity, they will make up for that by their greater number.) 
The atoms, in fact, concentrate the energy, or motion, existing in 
the ether ; for that quantity of energy which existed in a space 
proportional to the cube of their radii is, by their peculiar con- 
stitution, concentrated into a space proportional to the square of 
their radii only, viz., their surfaces. A rough analogy will perhaps 
help here. Suppose an air-tight vessel full of air at atmospheric 
pressure to contain a number of empty bladders with a tube 
attached to each, accessible from the outside of the vessel. If, 
through these tubes, the bladders were blown up full of air, it is 
easy to see that the pressure in the vessel would be increased, and 
the more the greater the number of bladders. In much the same 
way, then, would the pressure in the ether be increased by the 
creation of these atoms, or by an increase in their size. 
7. It will now, very naturally, be asked how can atoms such as 
these, with their various potentialities for increasing the ethereal 
pressure, be neutral at any time? In other words, how can the 
pressure in every direction be equal with atoms like these flying 
about? Or yet again, how is it possible to have the same 
electrical actions produced in the ether by atoms of different 
volumes ? The answer to this is not the least curious property of 
these atoms. Indeed, as I said already, the more their constitu- 
tion is studied the more marvellous will they appear. To answer 
the above shortly, I may say that the greater their quantity of 
electricity, or their potentiality for increasing the ethereal pressure, 
the greater proportion of it, through their collisions and vibrations, 
is converted into heat. Let me draw the reader’s attention again 
to what, according to this theory, a wave of heat is. When two 
atoms come together the independent particle movements which 
resist the in-crushing power of the ether, and which act within a 
certain area around the point of contact of the atoms, are, as it 
were, throttled ; the point of contact cannot resist the increased 
pressure brought to bear on it ; the atoms are therefore flattened 
in that locality ; the flattening produces a condensation of the 
particles, and when it has reached a certain point, over-balancing 
