PHYSICAL GEOGRAPHY. 41 



ticulars it greatly differs from the other river, with clear 

 waters and a moderate current. The fall of the Missisippi 

 from St. Peter's, and that of the Missouri from Pierre Chou- 

 teau, to the confluence of the two rivers, are in the ratio of 

 45 to 85, according to Nicollet, and therefore the average 

 rapidity of the Missouri is nearly twice that of the Missi- 

 sippi.* The great rapidity of current in the Missouri render- 

 ing that river difiicult of navigation, even by the power of 

 steam, in the upward voyage, is not the only obstacle, how- 

 ever, to the passage of boats upon it. Its velocity and force 

 constantly bring along and heap up sand bars, a characteris- 

 tic of nearly all the western rivers, except the Des Moines 

 and Rock Rivers, which have rocky beds. Beside the ac- 

 cumulating and shifting of sands, the same cause fills the 

 river w^ith planters, snags, and sawyers, which are all the 

 same thing, that is, drift w^ood partly buried in the sand so 

 as to hold in position, while projecting to the surface it pre- 

 sents a point upon which the boat strikes, and is wrecked. 

 The different names given to this kind of obstruction have 

 reference merely to the position in which they become fixed. 

 The Missouri in the lower part of its course is very tur- 

 bid, bringing down a great quantity of mud with its waters. 

 This character, it has been said, it loses above the Platte, 

 600 miles from its mouth. The difference in the descent of 

 its cun-ent above that point, as given by Nicollet, renders the 



From these measurements it appears the Missouri falls 106S feet in 1256 

 miles, or over 80 feet in .100 miles, and the Missisippi 356 feet in 786 

 miles, or over 40 feet in 100 miles, or 5J ins, nearly in a mile. The fall 

 of the Missouri is, however, unequal : in the upper 650 miles, starting from 

 Fort Pierre, the descent is 4S4 feet, a little over 8 inches to the mile : in 

 the remaining 600, to the mouth, it is 584 or 12 inches nearly to a mile. 



