60 



VARIETIES OF COAL. 



gSlery. of the s P acc becatne converted into flat land, where, under 



favourable conditions, the plants grew, by the decay and 



Wall-case 41. 



accumulation of which large strata of vegetable matter 

 were prepared for being mineralized, or changed into coal. 

 This was evidently effected by chemical changes, under 

 pressure caused by the accumulation of overlyino- strata. 



The coals (of the Coal Measures), may be broadly divided 

 into three kinds : common (" bituminous ") coal, anthracite 

 and cannel or parrot coal. Analyses of two varieties of 

 common coal, from South Wales, give the following re- 

 suits : 



Carbon 



Hydrogen - 



Nitrogen 



Sulphur 



Oxygen 



Ash 



71*08 

 4*88 

 0*95 



1*37 



17*87 



3*85 

 100*00 



- 90*94 



- 4*28 



- 1*21 



- 1*18 



- 0*91 



" 1>45 

 100*00 



An anthracite from Swansea gave : 



Carbon 



Hydrogen - 



Oxygen and Nitrogen 

 Ash - 



Loss 



- 92*06] 



- 2*33 

 2*53 

 1*58 

 1*00 



100*00 



Wales 



the same beds of coal sometimes change, by 

 degrees, from bituminous into anthracitic coals, in their pas- 

 sage from east to west. It will be observed that as a rule 

 anthracite coals are richer in carbon, and poorer in hydrogen, 

 than bituminous coal; and the change seems, in general 

 terms, to have been that a proportion of the carbon of the 

 coal went off in the form of carbonic acid, and another por- 

 tion as carburetted hydrogen. The proportionate quantity 

 of hydrogen thus diminished, whilst the carbon became 



t> 



ii soft : 

 H 0» 



Xhesp 



of them c 

 rep 



minus 



c 



H" fori 



n 



hM 



t 



b ? the h 



°f 4e G, 

 °f the G 



* i, G 

 itt 5l 



> sh< 



