N 



obtained in the distillation of Wood ^ l5fc, 17 



or that carbon which there is not oxygen enough present to burn, is 

 deposited in a state of very minute division in proportion as it is 

 volatihzed, during the formation of the naphtha or petroleum, the 

 more hydrogenous part of the compound. But if this part is sepa- 

 rated without flame, either by a more moderate heat, or by excluding 

 oxygen from it, the carbon is rendered apparent by its affinity of 

 aggregation, which causes it in the end to assume comparatively 

 refractory powers, and a more solid form. 



Such are the views I would entertain of the bituminous genus, in 

 which as it is found in Nature, all traces of organization or re- 

 semblance to vegetable and animal inflammable matter, have so 

 thoroughly ceased, that we are entitled to give its several species 

 a fair rank among minerals. But there is yet another division of 

 inflammable and subterraneous substances connected with these, 

 of which the claims may appear doubtful. Retaining as they do, the 

 traces of organization, and that sometimes in great perfection, it may 

 be often questioned whether they do not more properly rank with 

 the fossil remains, than with the minerals properly so called. They 

 are well distinguished by the name of Lignites. At one end of this 

 series is placed jet, in which the traces of vegetable origin are nearly 

 obliterated. Surturbrand and the several varieties of brown coal, 

 including Cologne earth, connect it gradually with submerged wood 

 and peat. The experiments I have already related prove that the 

 substance resembling bitumen, which is produced by the action of 

 fire in the ordinary way on vegetables, differs from it essentially, 

 and it has been seen that solubility in naphtha is the readiest crite- 

 ^ rion by which these substances can be distinguished. To assure 

 myself of the accuracy of this test I mixed the petroleum of coal 

 with the black oil of wood in several proportions, and by the appli- 

 cation of naphtha separated the one from the other. By this simple 



Vol. II. c 



