492 Transactions.— Chemistry. 
highly resinoid substance or a pure resin according to the time 
it has been exposed to the air. 
It only remains for us now to discuss the subject of the cause of the 
production of the figures in question, and for this I need not do more than 
point out to you, that if the nature of these figures is as I have just 
described, their cause—that is of course their more immediate cause—can be 
no other than the oxidation of a portion of the 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 wala be sufficient to name in 
answer to this question. Why 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 and 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 moore it, 
showing very clearly that the two substances cohere, 
