Sxzv,—On Tomlinson’s Cohesion Figures. 491 
Secondly, as to the ground of these figures, i.e., the part in which these 
annular spaces or markings are set. I found that when a small quantity of 
any oil is gently placed thereon it does not spread to any notable extent, 
but keeps nearly to the drop form; and it was further manifested to me 
that this part breaks into angular fragments, which are possessed of such 
rigidity that they keep to a tabular form no matter how they are dashed 
about. Now, as oils indiscriminately flow over oils, and as none of them 
can indurate to such an extent as would determine angular shapes to their 
fragments, it is clearly demonstrated that this part, ie., the ground of the 
pattern, is not an oil, 
The current idea, then, as to the nature of this di of the figure, being 
fallacious, it is necessary that we should adopt another. 
What this ought to be, a full consideration of the case will, I think, 
clearly show. Thus, owing to the great proneness of oils generally to oxidize 
to substances of a resinous nature when exposed to air, it is certain that in 
no instance do we, for the production of these figures, operate with an oil 
that is not, to a small extent, charged with such matters; and further, it is 
also as certain that the quantity of resinous matter therein must be very 
largely increased by the time that any cohesion figure made with it has 
passed to its final form. It being, therefore, undeniable that resinous 
matter forms one of the principal constituents of the cohesion figure in its 
ultimate condition, the conclusion forces itself upon us that of such matters 
is the material of their ground alone composed. This is really the only 
alternative, as it is one which meets all the requirements of the case. So 
attenuated, indeed, and so exposed are the thinner portions of these figures, 
and so rapidly is the kind of change indicated wrought upon oil under these 
conditions, that it is only reasonable to conclude that these portions are 
wholly composed of resin, to the exclusion consequently of any trace of oil. 
As being corroborative of the truth of the supposition that the presence 
of resin in the cohesion figures plays an important part in their production, 
I would inform you that the addition of about ten per cent. of resin to a 
good oil very much quiekens the production of cohesion figures, and also 
passes them through their various phases to the ultimate figure with & 
speed which is far greater than is to be observed in the case of the oil. 
And now I think the foregoing statements of facts and observations may 
be fairly held to demonstrate— 
1st. That the annular spaces or markings of Tomlinson’s cohesion 
figures are not depressions but protuberances, not holes but hillocks, 
and are not composed of water, but of oil. 
2nd. That the plane part of these figures the ground às it were of the 
pattern, is not oil (as heretofore quiescently allowed), but either a 
