350 Expedition to the 



are discharged early in the season, and wash from their 

 mouths the sand and mud, previously deposited therein, leav- 

 ing them free from obstructions. These freshets having sub- 

 sided, the more northerly branches discharge their floods, 

 formed by the melting of the snow at a later period. The 

 Missouri being swollen thereby, backs its waters charged 

 with mud, considerable distances up the mouths of the tri- 

 butaries before alluded to. The water here becoming stag- 

 nant, deposits its mud, and the tributaries having no more 

 freshets to expel it, remain with their mouths thus obstruct- 

 ed, till the ensuing spring. 



The lower part of the Canadian river, although it is inclu- 

 ded within the section under consideration, will be describ- 

 ed in the sequel of this report, in connection with the rest of 

 that river. 



Of the animals found in the several sections of country 

 above described, there are a great variety in almost every 

 department of Zoology. But as most of them are common 

 in other parts of the United States, they need not be enu- 

 merated here. 



V. Of the country situated between the Meridian of the Courh- 

 cil Bluffs and the Rocky Mountains. 



We next proceed to a description of the country, westward 

 of the assumed meridian, and extending to the Rocky Moun- 

 tains, which are its western boundary. This section em- 

 braces an extent of more than four hundred miles square, 

 lying between ninety-six and one hundred and six degrees of 

 west longitude, and between thirty-five and forty-two degrees 

 of north latitude. 



Proceeding westwardly from the meridian above specified, 

 the hilly country gradually subsides, giving place to a re- 

 gion of vast extent, spreading towards the north and south, 

 and presenting an undulating surface, with nothing to limit 

 the view or variegate the prospect, but here and there a hill, 

 knob, or insulated tract of table land. At length the Rocky 

 Mountains break upon the view, towering abruptly from the 

 plains, and mingling their snow capped summits with the 

 clouds. 



On approaching the mountains, no other change is observ- 

 able in the general aspect of the country, except that the 

 isolated knobs and table-lands, above alluded to, become 

 more frequent and more distinctly marked, — the bluffs by 

 which the vallies of water courses are bounded, present a 



