SOO REMARKS ON SANDSTONE AND 



soda. The granite which here rises from beneath the secon- 

 dary strata, is coarse, consisting of a large proportion of reddish 

 brown feldspar in imperfect crystalline masses. The mica 

 is black, and in small proportion. The granite is not com- 

 pact, and decays rapidly. Beinej separated probably by the 

 frost, it crumbles into small fragments, which roll down from 

 its steep declivities and accumulate in great quantities in the 

 small hollows and in the beds of streams. This rock rises 

 abruptly to a vast elevation, and probably extends far to the 

 west. 



These appearances are found on the southernmost of 

 those branches of the Platte which descend from the moun- 

 tains before their junction with that river. Proceeding still 

 southward, the sandstone ridges nearly disappear in the ele- 

 vated tract which divides the waters of the Platte from those 

 of the Arkansaw. The smooth and grassy plain is here ter- 

 minated by brown and naked piles of granite, which rise 

 almost perpendicularly into the regions of perpetual frost. 



The secondary district which lies beyond this ridge, has a 

 surface slightly inclined towards the north east, discharging 

 in a contrary direction several small streams into the Ar- 

 kansaw. The most striking feature of this region is consti- 

 tuted by certain moderately elevated tabular hills, with [)er- 

 pendicular sides and level summits, w!t ch are scattered irre- 

 gularly about the country, addina; greatly to its beauty. In as- 

 cending these hills, their sides are almost invariai*ly found to 

 be of coarse friable sandrock and loosely cemented, conglo- 

 merate. Above these, and forminsr the top of the hill, is usu- 

 ally a stratum of fine compact sandstone. It is also obvious, 

 on the slightest examination, that in the sides of those hills 

 which stand near each other, there are, at equal heia;hts on 

 each, corresponding stripes and beds similar in colour and 

 other particulars. These appearances are so constant as to 

 leave little doubt that the hills in question are the remains 

 of a formation of coarse sandstone which may formerly have 

 covered a great extent of the plain country iKirdering on the 

 mountains. From the nature of the cement, the fineness 



