16 COALFIELDS AND COLLIERIES OE AUSTRALIA. 



values." He then draws up the following table of proposed 

 groups of coal : 



Carbon-hydrogen ratio. 



Group A, (graphite) infinity to ( ?) 



Group B, ) (anthracite) (?)to30(?) 



Group C, ) 30 (?) to 26 (?) 



Group D, (semi-anthracite) 26 (?) to 23 (?) 



Group E, (senii-bituminous) 23 (?) to 20 



Group F, ^ 20 to IT 



Group G, / IT to 14.4 



Group H, f (bituminous) 14.4 to 12.5 



Group I, ) 12.5 to 11.2 



Group J , (lignite) 11.2 to 9.3 



Group K, (peat) 9.3 to (?) 



Group L, (wood cellulose) T.2 



Professor H. D. Rogers proposes the following as a commer- 

 cial clasification of coals : 



Volatile Matter Fixed Carbon 

 Per Cent. Per Cent. 



Anthracite below 6 90-94 



Semi-anthracite below 10 84-90 



Semi-bituminous . . between 12 and 18 52-84 



Bituminous above 18 T5-80 



Hydrogenous or gas coal, cannel, torbanite. 

 This classification, however, does not fit all cases; there is 

 no rigid division and some overlap. 



Varieties of Coal. 



Anthracite, hard or stone coal, is the hardest and most 

 lustrous of all coals. It gives great heat, burns with little 

 flame and no smoke. It is valued by man-of-war ships. Its 

 specific gravity varies between 1.3 and 1.7; it does not soil the 

 fingers, has a deep black color, but is sometimes iridescent, 

 when it is known as "peacock coal." The fracture is con- 

 choidal, lustre brilliant, and sub-metallic, or resinous to dull 

 "Dry coals" are those wanting in oily constituents, in con- 

 tra-distinction to "fat" or gas coals. 



Semi-anthracite. This is neither so dense nor so hard as 

 true anthracite. Its contents of volatile hydrocarbon is 

 greater and it ignites more readily. 



Semi-bituminous coal is generally not so hard as bitu- 

 minous coal, and its fracture is more cuboidal. The percent- 

 age of volatile matter is less. It kindles readily, burns with 

 a steady flame, and makes a good steam coal. 



Bituminous, or soft coals may be further subdivided into 

 coking or caking and free burning coals. The term "bitu- 

 minous" does not mean that these coals contain bitumen, 

 which as a rule they do not. Bituminous coal has a specific 

 gravity of 1.25 to 1.40, it is generally brittle, has a bright 



