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Having thus furnished you with the particulars of that chemical 
process by which an oil is formed from substances which would not 
a priori have been expected to yield it, we will now endeavour to 
ascertain how far that process resembles the presumed process of 
bituminization. In the first place, then, the substances acted upon, 
by the supposed bituminous fermentation, as well as by the vinous 
fermentation, are the same — dead vegetable matter. Secondly, as 
in the vinous fermentation, so in the bituminous fermentation, a 
peculiar acid and a peculiar combustible substance is formed ; 
those of each process resembling each other in their component 
principles ; this resemblance being particularly close between the 
combustible substances resulting from each process : each possessing 
a high degree of levity and inflammability ; each being formed of 
hydrogen, combined with a large proportion of carbon and of 
oxygen ; and each manifesting, that the principles of which they are 
composed are not in a very intimate state of union. 
I am anxious, before I conclude this letter, to place before you 
some of the reasons which have induced me to suppose the ligneous 
substance to be that part of vegetables which is most particularly 
acted on, by the species of fermentation which I have assumed ; 
as well as to point out to you a circumstance, which, in my opinion, 
yields strong, I had almost said internal, evidence of the necessity 
of such a species of fermentation. 
So generally is the ligneous substance diffused through the 
vegetable system, as to render it, perhaps, the most abundant of the 
consideration, which seems to corroborate this opinion, of the different steps of this progress to 
an oleaginous state, depending on certain added proportions of carbon, combined with oxygen, 
is, that oil itself, the vltimatum of this process, holds so considerable a portion of carbon, that 
this principle constitutes a large proportion of every one of its products, which are carburetted 
hydrogen, carbonic acid, and charcoal; whilst the quantity of oxygen which it contains is also 
so great, that it manifests a degree of acidity, in a very short time, merely by the addition of 
what it attracts from the air. 
