STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 121 



attain commercial importance. Two are near Aladdin, one of them, 

 2 feet to 3 feet 6 inches, the other, lo feet above, being thinner. 

 The extreme thickness is at a little way north from Aladdin where 

 the lower lens becomes 8 to 9 feet ; but both thin away, being re- 

 placed with impure coal, before disappearance. The coal at Aladdin 

 is soft and bituminous, as it is also at Sundance. In the Cambria 

 district, on southwest side of the region, there is an oval space of 

 about 10 square miles, in which the coal averages 5 feet, but, in the 

 surrounding area, the thickness decreases, the coal becomes impure 

 and carbonaceous shale replaces it. On the southern slope of the 

 Black Hills, a coal bed, 5 feet thick near Edgemont, is distinctly 

 local; it quickly disappears toward the southeast, giving place to 

 sandstone; while toward the northwest, it becomes merely a coaly 

 shale. There is little coal on the easterly side of the Black Hills, 

 only thin lenses of coal and coaly shale were seen, and these are con- 

 fined to the northerly portion. The thick bed near Aladdin has a 

 bone parting somewhat more than one foot thick, which, in appear- 

 ance, closely resembles cannel ; it has 38.69 per cent, of ash. The 

 upper part of the Lakota holds much petrified wood ; cycad stems 

 are numerous at several localities. 



Darton recognized his Cloverly formation on both sides of the 

 Bighorn Mountains in north central Wyoming, where, in much of 

 the region, the Dakota sandstone appears to be wanting. Streaks 

 of coal were seen occasionally in the Lakota, but they offer no 

 promise of economical importance. Fisher^^® saw Lakota coal in 

 the drainage area of No Wood creek at the westerly base of Big- 

 horn ]\Iountain. It is less than 50 feet above the Morrison forma- 

 tion and is found within a considerable area. One opening was 

 in a bed divided by a parting of 2 inches into benches, each 4 feet ; 

 but the coal is a lens and thins away rapidly on all sides. The 

 coal is dark with dull earthy luster, conchoidal fracture and re- 

 sembles carbonaceous shale ; but it is bituminous coal with not more 

 than II per cent, of ash. Fisher suggested that the formation might 

 be Dawson's Kootenai. No coal was seen by Woodruff within the 

 southwestern part of the Bighorn Basin and the formation appears, 

 according to Darton, to be barren in central western Wyoming, but 



lis C. A. Fisher, Bull. 225, 1904, pp. 355, 362. 



