282 The Origin and Relations of the Carbon Minerals. 



itation from sulphide of carbon or some other volatile carbon 

 compound by elective affinity. Laboratory experiments have 

 proved the possibility of producing it by such a process, but 

 the artificial crystals are microscopic, perhaps only because a 

 long time is required to build up those of larger size. 



Jet is a carbonaceous solid which in most cases is a true lignite, 

 and generally contains more or less of the structure of wood. 

 Masses are sometimes found, however, that show no structure, 

 and these are probably formed from bitumen which has separ- 

 ated from the wood of which it once formed part, and which it 

 generally saturates or invests. In some cases, however, these 

 masses of jet-like substance are plainly the residuum of excre- 

 mentitious matter voided by fishes or reptiles. These latter are 

 often found in the Tria?sic fish-beds of Connecticut and New 

 Jersey, and in the Cretaceous marls of the latter State. 



The discovery of a quantity of hydro-carbon Jelly, recently, in 

 a peat-bed, at Scranton, Pa., has excited some wonder; but simi- 

 lar substances (Dopplerite, etc.) have been met with in the 

 peat-beds of other countries ; and Avhile the history of the forma- 

 tion of this singular group of hydro-carbons is not. yet well 

 understood, and offers an interesting subject for future research, 

 we have reason to believe that these jellies have been of common 

 occurrence among the evolved products of the decomposition of 

 vegetable tissue in all ages. 



The generalities of the origin and relations of the carbon 

 minerals have now been briefly considered ; but a review of 

 the subject would be quite incomplete Avithout some refer- 

 ence to the theories which have been advanced by others, that 

 are in conflict with the views now presented. There have 

 always been some who denied the organic nature of the mi- 

 neral hydro -carbons ; but it has been regarded as a sufficient 

 answer to their theories, that chemists are agreed in saying that 

 no instances have come to the knowledge of man of the oocur- 

 rence in nature of hydro-carbons, solid, liquid or gaseous, in 

 which the evidence was not satisfactory that they had been de- 

 rived from animal or vegetable tissue. A few exceptional cases, 

 however, in which chemists and geologists of deserved distinc- 

 tion have claimed the possibility and even probability of the 

 production of marsh gas, petroleum, etc., through inorganic 

 agencies, require notice. 



