218 



RECORD OF SOIENCE FOR 1886. 



84. Newberry, in a paper on the Cretaceous flora ofNorth America,* 

 gives the followiug table which summarizes his views of the relation of 

 the diflerent local florae : 



85. In the long-delayed Census report on Mining Industries there 

 are several papers on the coal beds of the Northwest, the results of the 

 studies of Eldridge, Davis, and Willis for the Northern Transconti- 

 nental Survey under the direction of Purapelly. Willis' report is re- 

 ferred to under another heading. Eldridge t describes in great detail 

 the Montana coal-beds and their associated strata, and Davis reports 

 on the more general geologic relations of the district. The area studied 

 is included in a triangle 120 to 140 miles on a side in south-central 

 Montana, including the Bridger, Big, and Little Belt, Highwood, and 

 Main ranges. The rock series extends conformably from the Lower 

 Cambrian to the Upper Cretaceous, and is from 30,000 to 35,000 feet in 

 maximum thickness. The Cambrian schists are from 10,000 to 15,000 

 feet thick, but in some parts of the area are very much less and possi- 

 bly absent. These schists are capped by a persistent layer of quartzite. 

 and a limestone with Potsdam fauna. Overlying this, and separated 

 by a small interval of shales, there are 3,000 odd feet of Lower Carbon- 

 iferous limestones, generally overlain by a hard quartzite. Then there 

 are 15,000 feet or more of sandstones and shales of the Mesozoic in 

 which the occurrence of the Trias red beds is doubtful. Jurassic fossils 

 occur at 600 feet, many Cretaceous fossils at 3,200 feet, and the Creta- 

 ceous coal at 4,400 feet above the Carboniferous limestone, and con- 

 formable sandstones, with occasional imperfect plant-remains, extending 

 over 10,000 feet higher. All the post-Carboniferous about the mountains 

 appears to be Mesozoic, excepting Quaternary lake deposits in the 

 upper valleys, and some patches of possibly early Tertiary. Volcanic 

 rocks are found to have been extruded in greater part at the end of the 

 Cretaceous and Tertiary. The workable coal near Bozeman is only 

 3,700 feet above the Jura fossils, and is far below the Laramie. J 



86. In a paper read before the American Institute of Mining Engineers 



* New York Acad. Sci., Trans., vol. 5, pp. 133-137. 



t Tenth Census, report on Mining Industries, pp. 739-757. 



I Ibid., pp. 697-712. 



