obtained in the distillation ofWood^ l^c, 21 



Inflammability, I have proved to be a different substance, and that 

 the igneous theory of the origin of coal vp^ill receive no support from 

 them, as far at least as relates to the conversion of vegetable matter 

 into bitumen. I need take no notice of the modifications derived 

 from a mixture of animal matter in these experiments, as it is not 

 my desire to enter into a discussion of the general question, but to 

 state such chemical facts as arose in the experiments I undertook. 

 And since it is certain that vegetables alone are competent to the 

 production of bitumen, and that the geological history of coal does 

 not justify a supposition that animals have been concerned in its 

 production, it is perhaps unnecessary to investigate that question 

 further. 



To satisfy myself whether any essential chemical difference would 

 result from the experiments performed by simple heat, and those 

 performed by heat under pressure, I repeated these trials, by heating 

 wood in close gun barrels, introducing occasionally lime, clay, or 

 other matters to absorb the acid generated, and give the greater 

 chance for the disoxygenation and bituminization of the wood. 

 But the produce only differed from that of the experiments in open 

 vessels, by the circumstance which is mentioned in Sir James Hall's 

 paper, namely, the mixture of a porous charcoal, or a half destroyed 

 vegetable structure. In all cases the bituminous looking matter was 

 vegetable tar, not bitumen. 



Thus far then perhaps we are justified in concluding that the 

 action of water, and not that of fire, has converted the vegetable 

 matters into bitumen. It is another question to determine how that 

 bituminous matter in its several forms of peat or lignite, has been 

 converted into coal, into a substance differing mechanically, rather 

 than chemically from it, if, without misleading, I may use the con- 

 trast of these terms. 



