NARRATIVE OF THE EXPEDITION, 139 



Missouri, are from the Eocky Mountains and Ozark slopes, the 

 St. Francis, White, Arkansas, and Eed Eivers; and from the other 

 bank the Kaskaskia, the Ohio, Wolf, and Yazoo. It is estimated 

 to flow twelve hundred miles below the Missouri. Its width is 

 about one mile opposite St. Louis. It is narrower but more than 

 twice the depth at New Orleans, and yet narrower, because more 

 divided, at its embouchure at the Balize, where a bar prevents 

 ships drawing over eighteen feet of water from entering. 



No attempt has heretofore been made to determine the eleva- 

 tion of that part of the American continent which gives rise to 

 the Mississippi Eiver. From the observations made on the ex- 

 pedition, the elevation is confessedly less than would a priori 

 be supposed. If it is not, like the Nile, cradled among mount- 

 ains, whose very altitude and position are unknown, there is 

 enough of the unknown about its origin to wish for more infor- 

 mation. Originating on a vast continental plateau, or water-shed, 

 the superabundance of its waters are drained off by the three 

 greatest rivers of North America, namely, the St. Lawrence, the 

 Nelson's rivers of Hudson's Bay, and the Mississippi. Yet the 

 apex of this height of land is moderate, although its distance 

 from the sea at either point is immense. From the best data at 

 command, I have endeavored to come at the probable altitude of 

 this plateau, availing myself at the same time of the judgment of 

 the several members of the expedition. Taking the elevation of 

 Lake Erie above tide-water, as instrumentally determined, in the 

 New York surveys, as a basis, we find Lake Superior lying at 

 an altitude of six hundred and forty-one feet above the Atlantic. 

 From thence, through the valley of the St. Louis, and across the 

 Savanna summit, to the Mississippi, at the confluence of the Sandy 

 Lake Eiver, estimates noted on the route, indicate an aggregate 

 rise of four hundred and ninety feet. The ascent of the river, 

 from this point to Cass Lake, is estimated to be one hundred and 

 sixty-two feet; giving this lake an aggregate elevation of thirteen 

 hundred and ninety-three feet above the Atlantic. Barometrical 

 admeasurements made in 1836, by Mr. Nicollet, in the service of 

 the United States Topographical Bureau, place the elevation of 

 this lake at fourteen hundred and two feet above the Gulf of 

 Mexico,* being just twelve feet above these early estimates. The 



* Senate Document No. 237, 2G Con. 2d Session, A. D. 1843. 



