Expedition^ Cifc. 385 



rocks of the coal formation about the summit of the Alle- 

 ghany. Whether this conformation prevails in every part of 

 the range, our examinations have not enabled us to decide. 

 We know that some ot the granitic mountains of New Eng- 

 land, are far surpassed in elevation by the neighbouring hills 

 and ridges of mica slate, talcose rocks, or even more recent 

 aggregates. 



In the Ozark mountains, as far as they have been hitherto 

 explored, the granites and older primitive rocks are found at 

 the lowest parts, being surmounted by those of more re- 

 cent formation, the newer horizontal sandstones and strata 

 of carboniferous limestone, forming the highest summits- 

 The reverse of this is observed in the Rocky Mountains 

 —the granite there, far surpassing all other rocks, both in 

 extent and elevation, and forming the central and higher 

 portions of all the ridges; that range has therefore a character 

 very different from the Ozark or Alleghany mountains. 



It has been suggested by Major Long, that the hydrogra- 

 phy of the upper portion of the Missouri seems to indicate 

 the existence of a mountain range approaching that river from 

 the southwest, near the great northerly bend in the country 

 of the Mandans. From Lewis and Clark we have also some 

 accounts, tending to the confirmation of this opinion. Fur- 

 ther examination may perhaps prove that this third range, 

 called the Black Hills, resembles, in direction and general 

 character, the Alleghany and Ozark mountains. The Rocky 

 Mountains have not inaptly been called the back bone of the 

 continent; these three lateral ranges going off at angles of 

 about forty degrees, may with equal propriety be compared 

 to tile ribs. 



In latitude 38° north, the eastern base of the Rocky Moun- 

 tains is in about 106° west longitude. Following the same 

 parallel of latitude eastward, you arrive at the base of the 

 Ozark mountains, nearly in longitude 94"; the intervening 

 space occupying an extent of near twelve degrees of longi- 

 tude, is a sterile and desolate plain, destitute of timber; scorch- 

 ed in summer by the reverberation of the rays of the sun, — 

 chilled in winter by the freezing west winds from the Rocky 

 Mountains. Though we have assumed twelve degrees of 

 longitude as the medium width of this great plain, it is to be 

 remarked that, to many parts of it, our examinations have 

 not been extended. In latitude 41° no mountains, and 

 scarce an elevation deserving the name of a hill, occurs be- 

 tween the western spurs of the Alleghanies and the Rocky 



VOL. IT. 4^> 



