804 REMARKS ON SANDSTONE AND 



the country about the river Platte, which is an arid and ste- 

 rile jjlain of sand and 2;raveL 



From the Arkansaw to the sources of its lon.9;est tributary, 

 the Canadian, is a distance of al)out one hundred and tifty 

 miles in a direction nearly south. The district between th'se 

 two rivers is nearly plain, iiut the small streaiTis whicli tia- 

 verse it are sunk in deep and narrow valleys terminated by 

 precipices of sandstone similar to the valley of the Aikan- 

 saw. In tlie sides of these deep canals the rocks are so ex- 

 posed as to afford convenient op|)or'lunities for examining 

 a shor't distance into the internal structure of the plain. Her'e 

 as in the other districts which we have mentioned, the low- 

 est and almost the only rock found in the plains is sandstone, 

 This we shall consider as of two varieties, tlroirgh we do not 

 doubt tiiat those who are fond of system and of calling; liy 

 different names things which are essentially the sajne, would 

 be at no loss to discover here every variety of sandstone 

 hitherto dcsciil)ed, and perhaps many more. 



1. Red sandstone. 'F'his rock which is the lowest of the 

 horizontal or secondary rocks here met with, is very abun- 

 dant in all that part of the plain immediately sulyacent to 

 the Rocky Mountains which we have had the opportunity to 

 examine. A similar rock is met with ir) the eastern part of 

 the State of New York, and is there, as in the instance of 

 which we are speaking, placed near the borders of this 

 great secondary forrrration. I have never met with it in the 

 eastern part of the Mississippi valley. It occupies the coun- 

 try about the Canadian River, occurrina; on both sides most 

 of the way from its sources to its confluence with the Ar- 

 kansaw. It appears at intervals along the feet of the Rocky 

 Mountains, rejiosing against the primitive in a highly inclined 

 position. It vaiies in colour from vermilion red to dark 

 brown, and sometimes to various shadc^s of yellow and <i:rey. 

 Its cement is however almost invariably ferrirciinou'j. and the 

 predominance of red in tlie colourinc; cer-tainly entitles it to 

 the disttnctive appellauon of red sandstone. The lowest 



