184 



by which its constituent parts will be made to enter into new com- 

 binations. The hydrogen, uniting with the oxygen, is either vola- 

 tilized 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 compact- 

 ness of the superincumbent stratum of earth, not only the external 

 air is shut out, but the disengaged gaseous matters are prevented 

 from escaping, the bituminous 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. 



This I shall now attempt; and shall hope that, by comparing this 

 with the other species of fermentation, and by examining the results 

 of this process, we shall be able to form more reasonable conjectures 

 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 



