Page:Transactions of the Geological Society, 1st series, vol. 2.djvu/30

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Dr. Mac Culloch on certain products

Here the oxygen is completely dissipated, together with the azote, and the greater portion of the hydrogen. Analogous circumstances determine the putrefaction of animal matter, but in this case the play of affinities is so intricate, that a large portion of the carbon is volatilized in the gaseous form. By the constant affusion of water however, this process may be so modified, that the greater part of the hydrogen and carbon will be retained, and enter, together with minute portions of other gases, into a new compound resembling fat, which has obtained the name of adipocire. The analogy is strong, and the gradual deoxydation of the wood in this process is visible in the different stages of bituminization.

Such, as far as observations have yet gone, is our knowledge of this process and of the power of water in producing it. To repeat such an experiment in the laboratory seems impossible, since the necessary element of time must be wanting to complete it. But the action of fire being of shorter duration, and affording us also readier means of imitating Nature in those operations in which she has wrought with the same agent, it is worth our while to consider, if by it we can produce from vegetables the bituminous matters under review. It is not necessary to say how intimately this question is connected with our speculations on the origin of coal, since Sir James Hall's experiments were expressly intended to illustrate this view of the subject. In this, it is related that “coal” was produced, from “fir saw dust” by the usual method employed in these experiments, and that pieces of wood were changed “to a jet-black and inflammable substance, generally very porous,” in some specimens of which “the vegetable fibres were still visible.” There is no reason to doubt that the substance produced in these experiments, was that black matter which I have described in the first part of this paper, which, however resembling bitumen in colour and