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. 



