Rocky Mountains. 143 



ihe melting of the snows within the Rocky Mountains, the 

 cunent is proportionally accelerated, and becomes more 

 equable, running for many miles in succession, not less than 

 seven hundred and twenty feet per minute. At the time of 

 our ascent the summer floods had not entirely subsided, and 

 in contending against the current, we found occasion in a 

 few instances to make use of the towing rope. 



About thirtetn miles above the Grand Pass, is a point 

 where Lewis and Clark witnessed the falling of a portion, 

 about three-fourths of a mile in length, of a high cliff of sand- 

 stone and clay. Appearances have considerably changed 

 since the time of their journey. There is still an indentation 

 along the bluff, showing the upper part of the portion which 

 had slid down, but the whole is now covered with grass. 

 The river has retired from the base of the cliff it was then 

 undermining. A grassy plain, of some extent, occupies the 

 spot where the bed of the river must have been; but this 

 prairie is, in its turn, experiencing the vicissitude incident to 

 every thing along the bank of the Missouri, and is evidently 

 very soon to disappear entirely. A mile or two above this 

 point are cliffs of sandstone and indurated clay, in a state of 

 rapid disintegration. Here we observed extensive beds of 

 aluminous earth, of a dark gray colour, alternating with red 

 and yellowish white sandstone. Here are also numerous 

 vegetable remains, which Mr. Say thought to consist of the 

 limbs of trees included in the rock, carbonized and often in- 

 termixed with pyrites; smaller limbs in short fragments 

 lay intermixed, and crossing each other" in every direction. 



Among other things, we observed here what appeared to 

 be the cast of the seed vessel of the nelumbium, of uncom- 

 mon magnitude. Fragments of mineral coal were observed 

 scattered about the surface. • 



The mouth of the Platte* where we arrived on the 15th of 

 September, is, according to our observations, in latitude 41* 

 3' 13" ntrth. We shall hereafter have occasion to speak 



