682 Proceedings of Royal Society of Edinburgh. [sess. 
3. Before entering on the subject of electricity I should like to 
give what seems to me to be the explanation of “ Latent Heat,” 
which I very strangely omitted to consider in my former paper ; 
indeed the subject never entered my mind, although it was quite 
familiar to me, until thinking out the subject of my present paper, 
with which it is closely allied. Well, then, let us see what ac- 
count does the bubble atom give of “Latent Heat.” It is found 
that when a quantity of ice is melting the heat applied to this 
purpose disappears. The ice rises in temperature to the melting 
point and remains steadily at that point, no matter the quantity of 
heat applied, till the whole of it is melted. Afterwards the 
temperature of the resulting water rises, as the heat is continued, 
till it reaches boiling point, at which point it remains stationary 
no matter the quantity of applied heat, till it is all evaporated, 
Now what became of all the heat applied and absorbed during the 
times the thermometer was stationary ? It is said to have gone to 
change the state of aggregation of the molecules ; which is, no 
doubt, true, but after all this is only a hazy idea, and if the theory 
we are considering can give a clearer it ought to be a point in its 
favour. Well, then, according to this theory when two atoms, or 
bubbles, come together the ether in the medium within a certain 
area all round the point of contact of the globular atoms gets 
squeezed out, because the space inside of this area is too narrow to 
admit of the existence of an ethereal particle in it, as I have already 
said : hence the flattening of the atoms at their points of contact, 
also mentioned. The bubbles in fact partially collapse, and the 
more so the more they radiate out heat, drawing closer and closer 
together as they cool, their particles losing energy of position as 
they give out actual energy, the amount of flattening of their 
points of contact and the consequent amount of grip upon one 
another increasing hand in hand, till they have attained the 
temperature of their surroundings. Now this is what I should 
like to draw the attention of my readers to especially : — the loss of 
position by the particles of the atoms as heat is given out , i.e. the 
increase of collapse of the bubbles. Each particle, when originally 
elevated to the position where, along with its fellows, it helped to 
enclose a vacuous space, must have absorbed a quantity of energy 
proportional to the space enclosed and inversely as the number in 
