. 484 : Transactions, —Chemistry, 
before, as I think (this is, however, for measurement), and such 
surface will not allow kerosene or turpentine to flow over it; i.e. a 
drop of either put on keeps in nearly the drop form; in pure 
water they would flow over instantaneously. I have got the 
surface to refuse olive oil even, a very searching oil though a 
slow mover. This shows that such surface is a combination 
of camphor with water; and I am now enabled to fill up a 
break you would observe in the continuity of my paper. I 
now show how camphor forms some compound with water, 
which will not allow oil to flow over it. This compound 
is not camphor, because camphor is soluble in oil. I think it 
is probably the hydrate. If it is the hydrate, the surface should, 
by continued exposure, again rotate camphor, or allow oil to flow 
over it; and I find that two hours’ exposure of a non-rotating 
surface does restore to it the property of rotation. 
That vapour does not necessarily repel, seems shown by the fact 
that cork, on turpentine, or kerosene, is attracted by ammonia 
vapour. Now, ammonia is a substance which, being rapidly 
evolved—far more so than camphor—should repel cork on tur- 
pentine strongly. (Camphor, I may say, and ether, and alcohol, 
do repel cork on this liquid). 
Again: Turpentine vapour does not repel cork on turpentine, 
but it repels cork on water; and water offers more resistance to 
the movements of substances swimming on it than to substances 
swimming on turpentine. 
Clearly the idea that vapour in transit (molecular movement) 
can move masses of matter visibly to us, does not receive any 
support from such results as these. 
I am led to hold by researches here, and by thought on the matter, that 
the generally received idea that vapour exercises a direct repellent force, is 
entirely erroneous ; it appears to do so, but it in reality forms a compound 
with the liquid it appears to repel. A compound being lighter, or having - 
greater diffusive power than the normal liquid, rolls like a wave away from 
the supply, and carries any dust mechanically with it, giving the apparent 
repulsive effect observed. 
Repulsion by direet force of vapour is, I hold, an optical illusion, and 
one whieh physieists should long since have exploded by force of pure 
mathematical formule, and not left it as a job for chemists. 
I shall in a future paper take the larger subject, that no kind of matter 
can be visibly repelled while intercepting vapour in transit so long as a 
common temperature is observed and the pressure is not notably irregular. 
t 
E 
