JRocky Mountains. 393 



most of the materials of the sandstone are siliciou9, the rock 

 evinces a tendency to break into fragments of a rhombic 

 form, and in this case the elevated^edge presents an irregu- 

 larly notched or serrated surface. 



Sandstones consisting of silcx, with little intermixture of 

 foreign ingredients, are usually durable. But in the region 

 of which we speak, the variations in the composition, cement, 

 and character of the sandstone, are innumerable. Clay and 

 oxide of iron entering into its composition, in certain propor- 

 tions, seem to render it unfit to withstand the attacks of those 

 atmospheric agents, whose effect is to hasten dissolution and 

 decay. Highly elevated rocks of this description, may well 

 be supposed in a state of rapid and perceptible change. The 

 sharp angles and asperities of surface which they may have 

 originally presented, are soon worn away; the matter, con- 

 stantly removed by the agency of water from their sides and 

 summits, is deposited at their feet; their height gradually 

 diminishes, and even the inclination of their strata becomes 

 at length obscure or wholly undiscoverable. This appears to 

 have been a part of the process, by which numerous conic 

 hills and mounds have been interspersed among the highly 

 inclined naked rocks of this sandstone tract. These hills, 

 often clothed with verdure to their summits, add greatly to 

 the beauty of the surrounding scenery — while about the tops 

 of the more rugged and precipitous eminences, the deep 

 green of the small and almost procumbent cedars and juni- 

 pers, with the less intense colours of various species of de- 

 ciduous foliage, acquire new beauty from being placed as a 

 margin to the glowing red and yellow seen on the surfaces of 

 the rocks. 



II. — Sandstones of the Rocky ^fountains. 



Having commenced our account of the Rocky Mountains 

 with the consideration of that vast accumulation of rounded 

 fragments, constituting the great desert, which may be reck- 

 oned the most recent formation, depending upon that range 

 of mountains, we proceed to speak of the sandstones, the next 

 member in the inverted order we have adopted. And here 

 we take occasion to remark the peculiar grandeur and sim- 

 plicity of features, which distinguish the mineral geography 

 of this part of our continent. We have here a stupendous 

 chain of granitic mountains many hundred miles in extent, 

 with no stratified rocks resting about their sides except a few 

 sandstones almost equally granitic. We discover few traces 



VOL, II. 50 



