K« CARBON. 



is very brittle, and in mining there is consequently much 

 waste. It burns with a clear yellow flame. It occurs at 

 the Glasgow coal beds, and >3 named from its luster and 

 beauty. • fhe splint coal (or hard coal) of the same region 

 is harder than the cherry coal. 



Cannel coal is very compact and even in texture, with 

 littl« luster, and breaks with a large conchoidal fracture. It 

 takes fire readily, and burns without melting with a clear 

 yellow flame, and has hence been used as candles — whence 

 the name. It is often made into inkstands, snuff-boxes and 

 other similar articles. 



2L? " Brown coal, wood coal, lignite, are names of a less perfect 

 variety of coal, usually having a brownish black color,. and 

 burning with an empyreumatic odor. It has otten the struc- 

 ture of the original wood. The term broicn coal is, how- 

 ever, applied generally to any coal more recent in origin 

 than the era of the great coal beds of the world, although it 

 may not have any distinct remains of a woody structure, 01 

 burn with an empyreumatic odor. The name lignite has 

 sometimes the same general application, though without 

 strict propriety. 



X? c Jet resembles cannel coal, but is harder, of a deeper black 

 color, and has a much higher luster. It receives a brilliant 

 polish, and is set in jewelry. It is the Gagates of Dioscor- 

 ides and Pliny, a name derived from the river Gagas, in 

 Syria, near the mouth of which it was found, and the origin 

 of the term jet, now in use. 



Obs. Mineral coal occurs in extensive beds or layers, 

 interstratified with different rock strata. The associate 

 rocks are usually clay shales (or slaty beds) and sandstones ; 

 and the sandstones are occasionally coarse grit rocks. 

 There are sometimes also beds of limestone alternating with 

 the other deposits. In a vertical section through the coal 

 measures — as the series of rocks and coal seams are usually 

 called — there may be below, sandstones and shales in alter- 

 nating layers, or sandstones alone and then shales: there 

 may next appear upon the shale a bed or layer of coai, one, 

 two or even thirty feet thick ; then above the coal, other 

 layers of shale and sandstone ; and then another layer of 

 coal ; again shale and sandstones in various alternations, or 



What is cannel coal? brown coal or lignite ? jet ? How do beds of 

 coal occur, and what are the assoeinted rocks? 



