STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 131 



from the Raton-Trinidad field; VI. and VII. are from the Canyon 

 City field; VIII. and IX. from the Boulder District; and X. is from. 

 Platteville, about 40 miles north from Denver. 



The ash is high at the south, but the seams in the lower part of the 

 Vermejo group yield a fuel so good for steaming purposes that the 

 high ash becomes unimportant ; the ash decreases northwardly and 

 in the Boulder District it is about that of an ordinary good coal. 

 But in the same direction the type of coal changes ; in the Raton- 

 Trinidad field, one finds usually a high-grade bituminous coal, that 

 from some extensive mines yielding a strong coke ; in the Canyon 

 City field, the coal is still bituminous, but it does not cake and the 

 oxygen is about double that in the Trinidad coals ; in the Boulder 

 District, the coal is distinctly subbituminous, is xyloid in appearance 

 and disintegrates on exposure. There are no such violent con- 

 trasts betw^een proximate and ultimate composition, such as have 

 been recognized in some of the newer coals. 



The Fox Hills as a coal-bearing formation is important in south- 

 western Wyoming ; the Adaville seam of Uinta County has maxi- 

 mum thickness of 84 feet ; at least a part of the Black Buttes coal 

 group in Sweetwater County belongs here ; the coal assigned to the 

 Lewis in Carbon County is taken by the writer to be at a Fox Hills 

 horizon. The seams become thin and unimportant eastwardly. The 

 Adaville seam yields coal of almost the same composition at two 

 widely separated mines, which differs little from that of the Boulder 

 District in Colorado. The volatile in the coals of Uinta and Sweet- 

 water Counties varies from 38 to almost 49 per cent., though in the 

 coals compared the carbon is almost the same throughout The 



