AREAL DISTRIBUTIONS' OF THE LIGNITIC FORMATIONS. 9 



come in contact, the former is superimposed to the latter; and that really 

 the White River group formed a vast basin subsequent to the existence ot the 

 great lake on whicli the Lignitic sediments were deposited." He adds: 

 "We find also, by examining the White River group along the base of the 

 mountains, that the Laramie Range for.ncd a l>arrier that prevented it from 

 extending into the Laramie Plains; but the evidence is clear that at the tune 

 of the existence of the great Lignitie lake or sea, this barrier did not pre- 

 vent the water communication with the Laramie Plains. Lideed, the evi- 

 dence seems quite elear that, with the exception perhaps of some isolated 

 peaks rising above the waters, there was no mountain barrier where we have 

 n<,w the Laramie Range. Therefore, with the exception of the Bear River 

 aud Coalville group, we may connect the coal-bearing beds of the Laramie 

 Plains and Colorado with the vast group in the Northwest." 



The southern l)asin, generally named tlie Colorado Basin, is followed, 

 nearly without interruption, from a (.^^ miles south of Cheyenne to New 

 Mexico It is continuous to the South Platte below Denver, where it is 

 covered by a ridge of hills, the Monument Creek group, and then reappears 

 near Colorado City. On the Arkansas River, near Canon City, outlayers of 

 the Licuitic have been left upon the Cretaceous, which by denu.lation is 

 exposed over nearly the whole valley; and south of the Arkansas, or from the 

 Spiuish Peak the belt becomes continuous again to the Raton Mountains, m 

 New Mexico, with outlayers or isolated patches appearing as far south as 



Albuquerque. 



The southern Lignitic covers, therefore, an extensive area. It cannot 

 be estbnated, however, for the reason that it is cut by more recent deposits 

 at some places, as south of Denver, and by erosions along the Arkansas River, 

 and especially because its width from the mountains to the east is unknown. 

 The upheaval of tlie mountains has exposed the edges of the Tertiary strata 

 with those of the underlying formations, throwing them up into a series ot 

 hogbacks, which pass very abruptly from an inclined, even vertical position, 

 in the proximity of the mountains, to a horizontal direction toward the plains. 

 All along the mountains, the Lignitic is at the upper stage, and therefore it is 

 covered merely in passing to the plains by the more recent deposits of the 

 surface But how far it extends, or it is accessible for coal, has not ye been 

 ascertained. Shafts have been sunk east of Denver about ten miles, and thick 

 beds of coal or lignite have been reached at a moderate depth. Other 



