480 Transactions.— Chemistry. 
one cannot obtain a homogeneous sphere of it for use, or if one could it 
would at once lose its character and shape. The oil then being of necessity 
produced irregularly around the camphor spreads unequally from it, and in 
the act urges it in a direction which is away from that side on which there 
is the greatest output of oil; thus the camphor breaks through the oily 
film at its weakest part, and sets itself upon the edge thereof, which posi- 
tion it retains so long as there is motion produced. The movements of cam- 
phor are, in short, the joint results of the outward spread of oil along the 
water surface—the inertia or adhesiveness of this oil as regards what 
surface it thus occupies—and, lastly, the antipathy, as it were, which exists 
between the two, the camphor and its oil, whereby they refuse to associate. 
But the questions will now without doubt present themselves to you— 
Why should the oil spread so determinately over the water and retain the 
position thus gained so obstinately? and why should it appear to repel 
camphor? Unto such questions I might with propriety reply, that to 
entertain them here is not incumbent upon me, as I have now completed 
the task I set myself in this paper, by showing that camphor moves, as we 
have seen, upon water, for the same reason that solid particles occupying a 
water-surface move when oil is added. To treat such questions is really to 
take up another subject, and one which includes within its scope the 
behaviour of oils generally with water when in presence of it—a subject, 
moreover, which I had reserved for a further communication to you; but 
rather than leave the matter in hand in a state which may to some appear 
unfinished, I will trench upon these subjects so far as to make a few general 
observations thereupon in elucidation of these questions. It is, however, 
proper that I should premise these observations with a short statement of 
the prevailing opinion as to the reason of the extensive spread of even 
minute quantities of oil upon water under favourable circumstances, and 
their refusal to mix under other circumstances. 
According to these opinions, and these are both the popular and scien- 
tific ones, the spread of oil upon water is simply the result of gravitation in 
conflict with the cohesiveness of the oil, and the apparent antipathy which 
they manifest towards each other, is the result of an exertion of a repul- 
sive property innate in one or the other, or in both. Thus it seems to me 
that the possibility of chemical reactions being concerned in each of these 
operations has not been contemplated, and so, as I am persuaded, an 
important factor in both these problems has been left out of consideration. 
In opposition, then, to such opinions, I will maintain here that both the 
spread of oil upon water in thin films, and the apparent repulsion which 
may be seen to occur between the two, are brought about mainly through 
the satisfaction of chemical affinity, 
a anneal 
