OP Tin: AMERICAN ACADEMY. 



In a chapter on '• The ancient lakes of western America," Newberry 

 discussed •• the history of this old lake country, as it is recorded in the 

 alternations of : which accumulated :it the bottoms ol its water 



basil Geol. Surv. Terr., 1870 I L871), 333). 



Powell says that the bad-land rocks of the Green river basin "are Ihe 



iments of a dead lake, and are quite variable in lithologic character- 

 istics. We find thinly laminated shales, hard limestones, . . . crum- 

 bling bad-land rocks, and homogenous, heavily bedded Bandstom 



ilorado fixer of the west, L875, L50). Again, the sedimentary b 

 north ami south of the Uinta mountains, are d< scribed as having been 

 "deposited in waters whose shores were limited by the lower reaches of 

 the range; that is, they [the sedimentary heds] all yidence of lit- 



toral origin" (Ibid., 166). Incidental reference is made to lakes by the 

 same author when describing certain strata of the Green ri\er basin, in 

 such phrases as " the old shore line," "the old Bitter creek lake," "in 

 this great fresh-water basin," and " sands were accumulating in the bed of 

 the lake " (Geol. Uinta Mountains, 1876, 163-165). 



New ton's Geology of the Black Hills, as edited by Gilbert, describes 

 the "bed of gravel" at the base of the White river Tertiary formation 

 as "piles of loose pebbles, having all the appearance of a gravel beach 

 on the sea-shore. Indeed, it is evidently a shore deposit, the remain- of 

 the beach of the old fresh-water lake, formed before the waters attained 

 their greatest height and while they were sorting over material brought 

 by rivers from the neighboring Black hills." Further on, it is noted as 

 " worthy of remark that while the deposits of the Cretaceous, from the 

 demolition of which the White river Tertiaries were evidently largely 

 formed, are dark carbonaceous clays or shah-, the latter are notable for 

 their light color. This [g probably due to the making sedi- 



ment in shallow water, whereby the carbonaceous matter was oxidized, 

 leaving the accumulation nearly white in color. A similar phenomenon 

 is to lie seen in the work of the modern stream-. . . . The rationale 

 appears to be thai the finely divided silt derived from the Cretaceous 

 clays has by constant exposure to the air had its carbonaceous coloring 

 matter oxidized and burnt out" (Geol. of the Black Hills. 188, I 



An essay by Cope on the "Tertiary Formations of the Central Region 

 of the United Sta imer. Nat., .wi. 1882, 177-195) is naturally 



devoted for the most part to paleontological matter-, but it contains such 

 ats as the following : — "The general history of the succession 

 of the Tertiary lakes of the interior of the North American continent and 

 their deposits has been developed by the labors of various jistS, 



