482 Transactions. — Chemistry. 



them, so each of them — that is, the oil and camphor — can only respond to 

 their affinities for water ; to the water therefore they both keep, for its 

 possession they fight. It is a running fight, in which the oil having a 

 motion of its own communicates a part of this to the camphor, and so 

 appears as the pursuer. 



Summarizing, now, all that we have here arrived at, by way of 

 emphasizing the points I consider as fundamental to the theory I have 

 proposed, you perceive that I have maintained upon evidence, much of which 

 has been experimentally demonstrated, that the movements described by 

 camphor occupying a surface of pure water,, are neither due to the direct 

 impingement of vapour upon such surface, nor yet to any electrical effect, 

 but to the production of a compound of camphor with water, which, being 

 of an oily nature, spreads upon the surface of the water, and, in the act, 

 forces the camphor to describe the movements in question, precisely in the 

 same manner that oils generally, in their flow along the same kind of 

 surface, can urge away from them any sohd particles resident thereon. In 

 the actual process, directly that the camphor touches the water there is a 

 considerable but unequal output of this oil therefrom, and as this does not 

 dissolve in the water, nor volatilize, at nearly the speed at which it is 

 formed, it spreads principally upon the water, and retaining for the time 

 possession of all it thus overruns, it urges and keeps the solid camphor 

 away. 



As I have already stated, were the production of this compound equal 

 around the camphor, we should not see the camphor move as we have done ; 

 but this is in the nature of things impossible, as there is certain to be more 

 of it made at the instant of immersion upon one side of the camphor than 

 upon any other of equal extent, and so an initial movement and direction is 

 given to the camphor. When this direction changes, as it frequently does, 

 the output of oil has become greater upon a different side, or the cam- 

 phor, in its course, has got into contact with its trail ; when aU movement 

 ceases, the whole surface of the water, or at least that within a considerable' 

 distance of the camphor, has got enfilmed mth the oily compound, and the 

 camphor thus becomes oil-bound. 



As to the reason why the oil of camphor when in motion, or, indeed, 

 any oil in motion, should thus urge camphor about, I have attempted to 

 show that this is due to the fact that they have no affinity for each other, 

 but that each has an affinity for water, and so they have both a tendency to 

 keep in contact with it — in fact, they are adlaesive in relation to the water, 

 but neutral in regard to each other, hence the appearance of direct repulsive 

 effect — a kind of effect, which by^he-way^ I beUeve to be always due to 

 secondary action < 



