STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 135 



The coals of Dakota age are insignificant. The only ultimate 

 analysis shows that in one case, at least, the coal is high-grade 

 bituminous but with notable percentage of ash. 



The Kootenai is without coal south from the northern border of 

 Wyoming and there as well as in IMontana the coal is not of high 

 grade. In the Black Hills of Wyoming one finds extensive mines 

 at or near Aladdin. In one of those the water is from 14 to 18, the 

 ash from about 5 to 16 and the sulphur from 5 to 7 per cent., all in 

 freshly mined coal. Within Montana, the Kootenai coals become 

 important locally and are mined at many places in Cascade and 

 Fergus Counties. In the former county, the water is but 3.5 to 7.5 

 per cent, but the ash is from 14 to 21. Sulphur is less than 3 per 

 cent. The coal is bituminous, the carbon in pure coal being about 

 80 and the oxygen, barely 15 per cent. In Fergus County, the ash 

 within several districts is from 10 to 17 per cent, of the air-dried 

 coal; but only 3 out of 10 samples gave more than 10; the sulphur, 

 however, is much greater than in Cascade, being 5 per cent, and up- 

 ward. The percentage of carbon in pure coal is from 80 to 85 and 

 that of oxygen 9 to 15. But one analysis shows only 75 of carbon 

 with 19 of oxygen. ^*- 



The analyses published by Dowling^*^ show regional variation in 

 the coals of Alberta. The ash is highest in areas near the moun- 

 tains, where three districts have 13 to 22, 10 to 20 and 8 to 17 per 

 cent. In all other areas, it rarely exceeds 8 and is usually about 5. 

 The water is about 3 per cent. Sulphur is in small quantity, there 

 being one extensive region with barely a half per cent. The coal is 

 bituminous and often is caking. Anthracite is obtained in disturbed 

 districts. 



In reading the results of analysis as given above, one is in danger 

 of concluding that " clean " coal is the rule and " dirty " coal the 

 exception. Emphasis must be laid on the fact that samples for 

 analysis have been cut, for the most part, from mines in successful 

 operation or from promising exposures. Lenses yield the best coal 

 in the central portions ; toward the borders, their coal becomes dirty 

 and usually passes into carbonaceous shale. In many vertical sec- 



1*2 Bull. 22, pp. 305, 126, 127, 130-133. 

 143 D. B. Dowling, Memoir 53, pp. 74-79. 



