kocky 3fauntains. 38S 



extended down the Platte, much farther than at present. 

 Here, as in the great plain which extends from the base of 

 the Uralian mountains to Petersburgh, we meet with nu- 

 merous elevations or platforms, like islands in the midst of 

 an ocean.* The summits of these outlying- hills, are crossed 

 at equal altitudes by corresponding strata of sandstone, and 

 conglomerate. 



From the minute account given in the narrative of the 

 Expedition, of the particular features of this region, it will 

 be perceived to bear a manifest resemblance to the deserts of 

 Siberia. The soil and rocks are saline; plants allied to che- 

 nopodium and salsula are peculiarly abundant, as are the as- 

 tragali and others of the legumina, while trees and forests 

 are almost unknown. 



The surface of the sandy plain rises perceptibly towards 

 the base of the mountains, and becoming constantly more and 

 more undulating, is at length broken, disclosing some cliffs 

 and ledges of micaceous sandstone. Near the Platte, this 

 sandstone occurs in horizontal strata, sometimes cut through 

 by the beds of the streams, and forming low ridges parallel 

 to the Rocky Mountains. Whether they continue in an un- 

 interrupted line along the base of the mountains, we have not 

 been able to ascertain. They are separated from the first 

 range of primitive, by more elevated cliffs of a similar sand- 

 stone, having its strata in a highly inclined position. Behind 

 these, occur lofty but interrupted ranges of naked rocks, 

 destitute of any covering of earthy or vegetable matter, and 

 standing nearly perpendicular. At a distant view they pre- 

 sent to the eye the forms of walls, towers, pyramids and co- 

 lumns, seeming rather the effects of the most laborious ef- 

 forts of art, than the productions of nature. When surveyed 

 from the more elevated summits of the first granitic range, 

 these immense tables of sandstone, standing on edge some- 

 times almost perpendicularly, and sometimes inclining at 

 various angles towards the primitive, resemble the plates of 

 ice often seen thrown into a vertical position in the eddies, 

 and along the banks of rivers. 



Climbing to the summits of such of these hills as are ac- 

 cessible, and crossing their stratifications towards the primi- 

 tive, we observe appearances similar to those found in the 

 vallies, when circumstances enable us to push our inquiries 

 to a corresponding extent below the surface. Having crossed 



* Peonant's Arc. Zool. vol, i, p. 158. 



