Rocky Mountains. 3,79 



tance of about seventeen miles from its mouth, is the first 

 serious obstruction to its navigation, consisting of a limestone 

 bar, extending across the river, denominated the Big Chain. 

 Three miles above is another bar of a similar description. 

 The range of rocks, of which these appear to be a portion, 

 seems to extend across the point of land situated between 

 the Ohio and Mississippi, presenting itself again on the lat- 

 ter, at the Big and Little Chains, before mentioned. The 

 falls of the Ohio, at Louisville, are impassable for boats of 

 burthen, except in the higher stages of the water. Le Tart's 

 Falls and numerous other rapids, denominated ripples, are 

 also impassable for boats of any considerable burden, when 

 the river is at its lowest stage. In this state the river is ford- 

 able in numberless places. 



X. — Of the Great Valley or Basin of the Mississippi. 



This vast region, embracing more than twenty degrees of 

 latitude and about thirty of longitude, although it has been 

 explored in various directions by men of intelligence, is yet 

 but imperfectly known, and probably no country in the world 

 affords a more ample or interesting field for philosophic in- 

 vestigation. A thorough acquaintance with its geological cha- 

 racter, would, in all probability, lead to the most important 

 conclusions, in forming a correct " theory of the earth," 

 while a knowledge of its vegetable and mineral productions, 

 may be conducive to the comforts and enjoyments of a large 

 portion of the human family. All we shall presume to offer 

 under this copious head, will be a few general remarks rela- 

 tive to the position and conformation of the valley, grounded 

 almost exclusively upon the hydrography of the country, so 

 far as it has come under our observations. 



The valley is bounded on the west by the Rocky Moun- 

 tains, on the east and southeast by the Alleghanies, and south 

 by the gulf of Mexico. To the northward no precise limits 

 can be assigned as its boundary. Although many have sup- 

 posed that the waters of the Mississippi are separated from 

 those running northwestwardly into the Pacific Ocean, and 

 northeastwardly into the Atlantic, by a mountainous range 

 of country, yet from the best information that can be had on 

 the subject, the fact is quite otherwise. The old and alm(jst 

 forgotten statement of savage origin, viz, that " four of the 

 largest rivers on the continent, have their sources in the same 

 plain," is entitled to far more credit. The rivers alluded to 

 are the Mississippi, the St. Lawrence, the Saskashawin, and 



