130 IOWA ACADEMY OF SCIENCES. 



Per cent. 



Volatile matter 41.5 



Fixed carbon 51 . 



Ash 7.5 



The beds, as a rule, show no great lateral persistence. 

 Mining operations have demonstrated that one bed in 

 Ward county underlies tifty square miles of country, but 

 this is believed to be much more extensive than the aver- 

 age. Observations along the Little Missouri and in the 

 Bad Lands, where the lignite beds are often exposed along 

 ravines and canyons for miles continuously, show that 

 the floor on which they were laid down was often uneven, 

 and that they are inclined to thicken or thin out rapidly. 

 While one bed is thinning another may develop above or 

 below it, so that the lignite is continuous through large 

 areas, though there is diversity of beds. 



All of the workable lignite beds of North Dakota are 

 regarded as Laramie, though beds a few inches in thick- 

 ness in the eastern part of the state occur in the B:nton. 

 Fossil shells which included three gasteropod and one 

 pelecypod species, collected during the past summer at 

 three points — the same species being found at each point — 

 in clays intimately associated with the lignite, were identi- 

 fied by Mr. Charles Schuchert, of the Smithsonian Listitu- 

 tion, who reports that while the range of the species is. 

 somewhat extensive, all are indicative of the Laramie. 

 Similar determinations have been made in former years by 

 members of the staff of the United States Geological Sur- 

 vey. As it exists in North Dakota the Laramie consists 

 mainly of clays which are never fissile or shale-like in 

 character. From fat and joint clays they may gradually 

 become arenaceous till they pass into unconsolidated sand. 

 This is locally hardened into solid beds. The most exten- 

 sive sandstone in the state caps the high buttes in Billings 

 county, and is fifty feet thick. Most of the sandstones are 

 micaceous, the common mica being biotite. Strata which 

 are widely separated laterally and in the vertical scale as 

 w^ell, often show great similarity in composition. They 

 are commonly cross-bedded. The clay strata are marked 



