214 On certain Products ollained 



uated sometimes with maltha and saineti«)es with aspliaUum — 

 a distinction quite unnecessary if the supposition wore true. If 

 we conceive coal to he con)pouiuled in this way, it woukl he more 

 ohvious to consider it as furnied of cajhon and petroleum, since 

 by a reg(dated heat it can !)e separated into those two sul)stances. 

 The theory of the experiment is equally assumed, and the con- 

 clusions equally groundlefis, when it is inferred that of this com- 

 pound (coal) the carI)on alone possesses the power of decom- 

 posing the nitre, and tlia", the proportions of these supposed in- 

 gredients may thus be determined. The varying temperature 

 ot the nitre would necessarily produce considerable variations 

 and uncertainty in its action, and in the consequent accuracy of 

 the results ; but it is plain, that the effect of this contrivance 

 w;is to separate by a sort of distillation the petroleum which iire 

 elicits from coal, and that the method could neither be so accu- 

 rate as that of ordinary distillation, from tlie greater irregularities 

 to which it was subject and the difficulty of conducting it, and 

 that it proves nothing with regard to the composition or .nature 

 of coal. In the exanunation of maltha, and asphaltum, the de- 

 fect of this method is still more apparent. If heat and flame be 

 applied to these bitumens, with access of air, they are either 

 ponsumed without leaving any carbon, or that carljon which there 

 is not oxygen enough present to burn, is dej)osited in a state of 

 ^•cry minute division in proportion as it is volatilized, during the 

 formation of the naphtha or petroleum, the more hydrogenous 

 part of the compound. Rut if this part is separated without 

 flame, either by a more moderate heat, or by excluding oxygen 

 from it, the carbon is rendered api)arent by its affinity of aggre- 

 gation, which causes it in the end to assume comparatively re- 

 fractory 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 

 resemblance to vegetable and animrd inflammable matter have 

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

 ^pccics a fair rank among minerals. But there is yet another 

 flivision of inflammable and subterraneous substances connected 

 with these, of which the claims may apj-ear doubtful. Retaining 

 :^i they do the traces of organization, and that sometimes in 

 great perfection, it may be often questioned whether they do 

 not more propc-i-ly 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 oijliterated. Sur- 

 turbrand and the several varieties of brown coal, including Co- 

 logne earth, connect it gradually with submerged wood and peat. 

 The experiments I have already related prove that the .substance 



rpsetubling 



