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by which its constituent parts will be made to enter into new 
combinations. The hydrogen, uniting with the oxygen, is either 
volatilized in water, or, combining also with a portion of carbon, is 
separated as carburetted hydrogen gas : the remaining portion of 
hydrogen giving colour and odour to the mass. Of the carbon, 
that which is not engaged with the hydrogen, either unites with the 
oxygen, and forms carbonic acid, or constitutes a part of the 
magma, of which, however, by far the most considerable part 
is the earthy matter, which entered into the composition of the 
vegetable. 
But if, instead of being thus exposed to the influence of the air, 
a mass of dead vegetable matter be accumulated in such situations 
as allow of the admission of water; but in which, by the compactness 
of the superincumbent stratum of the earth, not only the external 
air is shut out, but the disengaged gaseous matters are prevented 
from escaping, the hituminous fermentation I suppose to take place ; 
and bituminous matters are formed in various degrees of maturity 
and purity according to the stage at which the process may have 
arrived, or to the extraneous matters which may have been ad- 
mitted. — But I do not, however, wish you to forget, that, of the pro- 
cess I have here described, I am not able, for the reasons already- 
given, to adduce direct proof ; the proofs of its having taken place 
must be obtained by inference, and from analogy. 
I shall now endeavour to produce these ; and shall hope that, by 
comparing this with the other species of fermentation, and by ex- 
amining the results of this process, we shall be able to form more 
just opinions as to the nature of the new combinations into which 
the principles have entered. 
The substance, then, which I conceive to be entirely dependent 
on, and actually the product of this process, is bitumen ; a sub- 
stance which manifests, upon examination, all those properties which 
