8 Expedition to the 



south, seems in a great measure independent of it. From the 

 most elevated part of the continent, at the sources of the 

 Platte, and Yellow Stone branches of the Missouri, the de- 

 scent towards the Atlantic, is at least twice obstructed by 

 ranges of hills nearly parallel, in direction, to each other. 

 Erroneous impressions have heretofore prevailed, respecting 

 the character of that part of the country called the Missis- 

 sippi Valley. If we consider attentively that extensive por- 

 tion of our continent, drained by the Mississippi, we shall 

 find it naturally divided into two nearly equal sections. This 

 division is made by a range of hilly country, to be hereaf- 

 ter particularly described, running from near the north-wes- 

 tern angle of the Gulf of Mexico north-eastwardly to Lake 

 Superior. Eastward, from this range, to the summit of the 

 Alleghanies, extends a country of forests, having usually a 

 deep and fertile soil, reposing upon extensive strata of ar- 

 gillaceous sandstone, compact limestone, and other seconda- 

 ry rocks. Though these rocks extend almost to the highest 

 summits of the Alleghanies, and retain even there the hori- 

 zontal position which they have in the plains, the region 

 they underlay, is not to be considered as forming a dis- 

 trict of table lands. On the contrary, its surface is varied 

 by deep vallies, and lofty hills; and there are extensive tracts 

 elevated probably not less than eight hundred feet above the 

 Atlantic ocean. The north-western slope of the Alleghany 

 mountains, though more gradual than the south-eastern, is, 

 like it, divided by deep vallies, parallel to the general direc- 

 tion of the range. In these vallies, many of the rivers, which 

 derive their sources from the interior and most elevated hills 

 of the group, pursue their courses for many miles, descending 

 either towards the south-west, or the north-east, until they 

 at length acquire sufficient force to break through the oppos- 

 ing ridges, whence they afterward pursue a more direct 

 course. As instances, we may mention the Alleghany river, 

 which runs nearly parallel, but in an opposite direction, to 



