134 Mr* Hatch ETT'i Obfervations on Bituminous SubJIances. 



JET. 



Jet is a fubftance well known to be of a full black, fometimes 

 however inclining to brown. It is confiderably harder and lefs 

 brittle than afphaltum. It breaks with a conchoidal fracture, and 

 the internal luftre is glafly. It has no odour except when heated, 

 and it then refembles afphaltum. It melts in a ftrong heat, and, 

 when burned, leaves an earthy refiduum* 



Wallerius confidered jet as afphaltum which had become indu- 

 rated by time, and Mr. Fourcroy is of the fame opinion*. Others 

 again have arranged it with the varieties of coal f. I am inclined 

 however to believe, that it is neither afphaltum nor coal, but, 

 an intermediate fubftance which may be regarded as the firft. 

 gradation from the fimple bitumens into thofe which are compound. 

 The matter of afphaltum undoubtedly enters into it in a large pro- 

 portion, and has confequently ftamped feveral of its characters 

 upon it ; but the increafe of carbon, and of the extraneous or 

 earthy matter which is intimately mixed or rather combined with 

 it, has had fo much influence, that the charaaers of coal 

 are alfo in fome meafure apparent, and are rendered the more 

 linking by the fimilarity of certain local circumftanccs which 

 attend thefe two fubftances. The characters of coal are however 

 by no means fully eftablifhed in jet, but from this we pafs imme- 

 diately to another, in which thefe charaaers cannot be queftioned* 



This is the fubftance called 



CANNEL COAL, 



which is of a full black, of a fmooth, folid, even texture j it breaks? 

 in any direction* and the tranfverfe nature is conchoidal. It 



* Element d'Hi/l. Kat. et de Cfrtnie, torn* iii. p. 456". 

 f V/idenmamCs Hahdbuch der Mineraicgxs ) p. 628. 



burn!» 



