Skey. — On the Movements of Camphor on Water. 481 



I will only now take to task, in a direct way, the idea tliat oil and water 

 mntually repel each other. 



If any one will put a slender stick of some solid fat into water and 

 then remove it so that the lowermost point thereof is about one-twelfth of 

 an inch above the water-line, he will upon due examination find that a 

 portion of water adheres to the fat and joins it to the remaining water. 

 Some fats may be lifted out of water to a much greater distance than this 

 before connection therewith is broken. Now, you will perceive that these 

 effects are quite incompatible with this idea of repulsion ; could fats repel 

 water, they would rather depress water when applied thereto than raise it. 



A cohesiveness so strong as this can, as I believe, only be explained''-' by 

 assuming that a chemical combination has taken place between the fat and 

 the water, a combination not of masses but of surfaces, because of the 

 insoluble nature of the product in relation to both the substances furnish- 

 ing it. 



What is true here of fat will undoubtedly be true of the oil it furnishes. 



Allowing, then, that oil and water have affinities for each other, these 

 will certainly come into play to a very great extent as regards the oil when 

 a very thin film of it has contact with water, such as obtains when a drop 

 of oil is suffered to extend itself upon water unchecked, and the fact that 

 oils thin out in this way, and so rapidly as they do, upon water, I would 

 attribute in largest measure to successful exertion on their part to satisfy 

 this affinity. Corroborative of the truth of this opinion is the fact which 

 I have ascertained that oils spread far more rapidly and extensively upon 

 water than upon mercury, a substance which as far as we know has not 

 any affinity for them ; and in further corroboration of this, oil, as we have 

 already seen, does not spread at all when applied in small quantity to 

 water which is covered with hydrated camphor; still, each of these sur= 

 faces — the metallic and the camphoretted — may appear to us as smooth as 

 that of the purest water. 



And now applying the knowledge of these results and the deductions 

 they seem to allow us to make to the elucidation of the questions which 

 I have proposed on your behalf, I would maintain that this camphor oil, 

 though in part composed of water, has still an unsatisfied affinity for water 

 by which ib is urged to extend itself around in search of it; it occupies 

 firmly the surface it has thus overrun by reason of its internal cohesiveness, 

 its inertia, and its affinity for water. 



It forces the parent piece of camphor into movement, because being 

 saturated with camphor there is no unsatisfied affinity existing between 



* That this effect is not produced by atmospheric pressure is certain from the fact 

 that the whole of the portion wetted may be open to the air. 



&8X 



