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It is reasonable to conjecture, he thinks, that the remains of 

 vegetables, accumulated in large heaps, and exposed to the effects 

 of those particular combinations which occasion the heat of certain 

 mineral waters, or to the influence of volcanic fires, may have un- 

 dergone a real distillation ; and that the substances thus formed, 

 meeting with water which impeded their further decomposition, 

 have been carried to the surface of the earth, and appear there 

 under the form of naphtha, &c. Under other circumstances, he 

 conceives, that these same oils, thus detached by distillation from 

 the wood, have filtered insensibly into the beds of sand and clay, 

 and thus have produced the formation of coal and bituminous 

 schisti ; whilst, under other circumstances, these oils, accumulated 

 in the interior cavities of the earth, have assumed the consistence 

 which we observe in mineral pitch. 



To the opinion of Mons. Tingry, respecting the gradual decom- 

 position of vegetable matter, I certainly cannot object ; but later 

 observations, and particularly those of Mr. Hatchett, have clearly 

 demonstrated, that, however difficult it may be to account for the 

 different states in which the bitumens are found to exist, the action 

 of subterraneous fires, and the operation of distillation, cannot have 

 been the agents which have occasioned those varieties, in the forms 

 under which these substances appear to us. It may be proper to 

 remark, with respect to this supposed influence of subterranean 

 fires, that Dr. Hutton, and many of the French chemists, have 

 adopted the same idea, and to as considerable an extent. 



Dr. Darwin was of opinion, that morasses seem to have under- 

 gone a, fermentation ; but that the formation of coal depends on a 

 distillation similar to that which is supposed by Dr. Hutton. The 

 Doctor says, that " woods in uncultivated countries have grown 

 and fallen through many ages, whence morasses of immense extent;" 

 or, as he expresses it, 



