212 GEOLOGICAL SUEVEY OF THE TEEEITOEIES. 



abiindauce of water for a broad strip of land along the eastern flank 

 of the range. Not only are they rugged in general outline, but also in 

 minute detail, being exceedingly rocky and jagged, except in some of 

 the parks and larger depressions, where the local drift has rounded the 

 lower hills. As a general thing, they are covered with heavy forests of 

 pine and fir, except where the altitude exceeds the line of arborescent 

 vegetation. I would call special attention here to this fact, as I wish 

 to allude to it hereafter — the connection between the rugged, rocky sur- 

 face and forest growth. In the parks and other spots where there are 

 heavy deposits of drift, evidently brought down from the surrounding 

 heights, as a general thing there are no forests, occasional groves of 

 stunted cedars or i)iiions being the chief exceptions. 



Along the east base, after passing Box Elder Creek, going south, 

 long straight-lined foot-hills are often to be seen shooting out from the 

 mountain side, their tops fiat and almost or quite level. They are gen- 

 erally very smooth, without forest growth, but grassed over as evenly 

 as a mown meadow. These singular formations constitute a very re- 

 markable feature of this section, and give a peculiar charm to the land- 

 scape. An occasional "mesa" or squarely truncated hill can be seen 

 here, but these are more characteristic of the country farther south. 



As we approach the borders of Kew Mexico the mountains gradually 

 diminish in height, the mass separating into more regularly continuous 

 ranges ; the naked crests of the higher ridges often sharply serrated. 

 The sides, though rocky and deeply and sharply furrowed, are hardly 

 so rugged as farther north. As might be inferred from these character- 

 istics, the accumulations of snow are less extensive, the water more 

 rapidly carried ofl", and the streams less permanent than in the vicinity 

 of the mountains farther north in Colorado. 



The Eaton Mountains, which run east from the main range, near the 

 dividing line between the two Territories, form a rather singular excep- 

 tion to the general direction of the eastern ranges. In their external 

 features they are much like the mountains with which they connect in 

 some respects, while in others they remind us more of some of the 

 mountains in Southeastern Kentucky. They are tolerably well timbered, 

 much of it being of a very fine quality. They give rise to the Purga- 

 tory and Cimarron Elvers. 



Passing over this range to the south side, one of the most striking- 

 features of the landscape is the large number of isolated "mesas." 

 These singular elevations, in the form of truncated cones or pyramids, 

 with flat and horizontal tops and sharp outlines, rise up from the level 

 plains, or from the surface of a broad valley, and almost invariably 

 without any lateral connection with any other elevated ground. In ex- 

 tent they are widely different, some iiresenting a table surface of but a 

 few acres, while others have nearly as many square miles. It is evident 

 that these are beyond the reach of irrigation, from any natural reser- 

 voirs or streams, their only value being as grazing fields. 



This eastern mountain group appears to have two culminating points 

 or radiating centers ; the northern, and principal one, lies immediately 

 around the JSTorth and Middle Parks, and forms the rim of these elevated 

 basins ; the other lies immediately southwest of South Park. In the 

 first of these, Blue Eiver, White Eiver, Bear Eiver,* North Platte, and 

 a number of the tributaries of South Platte, take their rise. In the 

 other. Grand Eiver, the Eio Grande, Arkansas, and main branch of the 

 South Platte have their sources. The parks act as huge cisterns for the 



* This is not the Boar Eiver of Salt Lake Basin, but connects with Green Eiver. 



