492 Transactions. — Chemistry. 



highly resinoid substance or a pure resin according to the time 

 it has been exposed to the &h\ 

 It only remains for us now to discuss the subject of the cause of the 

 production of the figures in question, and for tliis 1 need not do more than 

 point out to you, that if the nature of these figures is as I have just 

 described, their cause — tliat is of course their more immediate cause — can be 

 no other tlian the oxidation of a portion of tlie oil employed to produce 

 them, and the aggregation of the remainder into annular patches to form 

 the markings which characterize them. 



How oil and resinous matters do thus dissociate, is a question which is 

 scarcely within the scope of this .paper to discuss. It is, however, one of 

 such interest, and is moreover so intimately connected with my subject, that 

 I cannot refrain from doing this in a brief manner, although to do so some- 

 what trenches upon a subject which I intend soon to treat of in a further 

 communication to you. 



According to ideas now in vogue, one word would be sufficient to name in 

 answer to this question. AVhy do these two substances dissociate ? And 

 that word is repulsion. The resinous parts of these figures would be held in 

 accordance with these ideas to repel the oily part. 



But from several observations I have recently made, I have reason for 

 asserting that this appearance of repulsion is at bottom due to the effects 

 of cohesion. One of these observations is that greasy matters generally, 

 contrary to present scientific and popular opinion, instead of repelling water, 

 adhere thereto when placed in juxtaposition with it.* 



The phenomenon of dissociation then has, I consider, to be explained by 

 a hypothesis in which the property of cohesion only has to be taken into 

 account, and I would form it as follows : — Oil has a certain degree of 

 cohesion for itself, also for water ; but the products arising from its oxidation 

 have a greater cohesion both as among themselves aiud for water, and 

 it is in direct proportion to the degree in which they are chemically 

 removed from the oil which furnishes them ; until, as the final products of 

 this process are reached, a notable affinity for water (that is an intense 

 cohesion) developes ; but this great cohesion for water on the part of such 

 products is attained only by a corresponding loss of cohesion between them 

 and the oil, that is the unaltered or less altered oil. These products 

 therefore have a constant tendency to monopolize the surface of the water 

 upon which they are formed, and the unaltered or but slightly altered oil, 



* If solid grease is placed in contact with water, the water-surface in the immediate 

 vicinity of the grease is not depressed below the general surface of the water ; and if the 

 grease is lifted just above this surface, the water in its vicinity is also lifted above it, 

 showing very clearly that the two substances cohere. 



