MODE IV. LIGNITE. 585 



they spread in burning, is pungent, often fetid, 

 and has no analogy with that of coal or bitu- 

 mens. They burn with a clear flame, without 

 bubbling or caking like coal, or running like so- 

 lid bitumens. They leave powdery ashes like 

 those of wood, but often in greater quantity, 

 more ferruginous, and more earthy : they seem 

 to contain a little potash *. These combusti- 

 bles give an acid by distillation, which coal does 

 not. 



" Lignites vary in colour from deep and 

 shining black, to an earthy brown : the texture 

 of the greater part of the varieties indicates their 

 origin, and gives rise to their name. The woody 

 tissue is often observed, though sometimes it has 

 wholly disappeared. The fracture of lignite is 

 compact, often resiniform and conchoidal, or 

 shining and straight. 



" The external characters of the varieties of 

 the species differ too much among themselves, 

 to allow them to be farther generalised. 



" 1. Lignite jet ^. It is hard, solid, compact, 

 and capable of receiving a very bright polish ; 

 it is opake and of a pure black ; its fracture is 

 undulated, and sometimes shining like that of 



" * M. Mojon found about 3 in 100 in the ashes of the bitu- 

 minous wood of Castelnuovo. 



" f J et > Hau}' Peckkohle, piciform coaL Brock." 



