STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 121 



tion by Hoffmann^''" must answer. He recognized a gradual change 

 in the chemical and physical character of the upper Mesozoic coals 

 from east to west within the Bow and Belly river region of western 

 Canada. In the eastern strip of that district, the fuels have all the 

 characteristics of lignite (brown coal) ; those of the middle strip are 

 intermediate between lignites and true coals, the latter being found 

 in the w' estern strip ; while in the mountains, farther west, anthracite 

 occurs. All belong to the same general horizon in the Upper Cre- 

 taceous. Reasoning from the series of analyses which he had 

 made, he grouped the fuels into lignites, lignitic coals and coals. 

 Lignites are fuels which, on exposure to the air, tend more or less 

 to. disintegrate and tp fall to pieces ; they all communicate a deep 

 brownish red to boiling solution of caustic potash and contain lo to 

 15 per cent, of hygroscopic water, sometimes even more; they do 

 not yield a coherent coke. Lignitic coals show much less tendency 

 to disintegration, give less deep coloration to the potash solution, 

 have less hygroscopic water, 5 to 9 per cent., and are practically 

 non-caking. Coals are hard and firm, give only slight coloration 

 to the solution of caustic potash and yield a non-coherent coke by 

 slow coking, but a firm coke by fast coking. In the relations of car- 

 bon, hydrogen and oxygen they closely resemble some British non- 

 coking coals. This grouping is very similar to that used by the 

 United States Geological Survey, which is, lignite, subbituminous 

 and bituminous coal. 



Coal has been found in all portions of the Tertiary column. 

 Pliocene deposits of some economic importance have been found in 

 Italy, Hungary, Germany, New Zealand and Alaska. The Mio- 

 cene coals of Hungary, Bohemia, Germany, Bosnia, France, Spitz- 

 bergen, Iceland and Greenland as well as those of Trinidad and the 

 adjacent portion of South America are of great extent ; coal of this 

 age has been found in Central America and occasionally in North 

 America, but the deposits are apparently unimportant. Oligocene 

 coals are mined extensively in Hungary, Germany and Switzerland, 

 but they have not been recognized definitively in North America ex- 



i*"' G. C. Hoffmann, " Chemical Contributions to the Geology of Canada," 

 Rep. Prog. Geol. Surv. Canada, 1882-4, Pt. M, pp. i, 2, 5-8; Ann. Rep. li 

 Pt. R, pp. 9-18. 



