Rocky Mountains. 377 



higher up, that are composed of coarser materials. In con- 

 sequence, the beds of the river are rendered narrower and 

 deeper to*vards their mouths than at greater distances above 

 them. This is more particularly the case with the Missis- 

 sippi, Red, Arkansa, and some others, whose beds or chan- 

 nels gradually dilate and become more shoal, on ascending 

 from their mouths. Thus it happens, also, that the naviga- 

 tion of the Mississippi has fewer obstructions between Natch* 

 es and its mouth, than above, this part of the river having so 

 great a depth of water, that snags, bars, &c. are sunk below 

 the reach of every kind of water craft employed in its navi- 

 gation. From Natches upward, to its confluence with the 

 Missouri the river presents impediments that become more 

 and more numerous and difficult to pass. Still, however, the 

 main channel, though intricate in many places, affords a suf- 

 ficient depth of water in all stages for boats of five or six feet 

 draft to ascend to the mouth of the Ohio. From this point 

 to the Missouri, a distance of more than two hundred and 

 twenty miles, the navigation is partially obstructed during a 

 very low stage of the water by shoals, so that it is navigable 

 only for boats of moderate burthen, requiring but about three 

 feet of water. At the distance of about thirty miles above 

 the mouth of the Ohio, there are two rocky bars extending 

 across the Mississippi, called the Big and Little Chains, 

 which in the deepest channel across them afford no more 

 than five or six feet of water, in a low stage, and occasion a 

 great rapidity of current. The Mississippi is usually at its 

 lowest stage about the middle of August, the summer fresh- 

 et of the Missouri having subsided previously to that time. 

 It usually continues in this stage till it is swollen by the fall 

 freshet of the Ohio, after which it subsides again and re- 

 mains low during the winter. The distance from New Or- 

 leans to the mouth of the Missouri, is estimated at about 

 twelve hundred miles. Its current in the main channel of 

 the river is supposed to have an average velocity of 3 3-4 

 miles per hour in a moderate stage of the water, but when 

 the river is high its velocity is considerably accelerated. Its 

 water is turbid, being charged with a fine argillaceous mud, 

 of a light colour, derived exclusively from the Missouri. 



The Missouri is a very wild and turbulent river, posses- 

 sing the ruder features of the Mississippi, but destitute of 

 the gentleness characteristic of the latter in many places. 

 The obstructions to the navigation of the Missouri, although 

 they are of the same character with those of the Mississippi>, 



VOL. II. 48 



