The north-western slope of that range of mountains, known collectively as the Alleghanies, has a moderate inclination towards the bed of the Ohio, and the St. Lawrence, which run nearly in opposite directions along its base. This mountain chain extends uninterrupted along the Atlantic coast, from the Gulf of St. Lawrence south-west to the great alluvial formation of the Mississippi. It crosses the St. Lawrence at the rapids above Quebec, and has been supposed to be connected as a spur to a group of primitive mountains occupying a large portion of the interior of the continent, north of the great Lakes.[005] An inspection of any of the late maps of North America, will show that this range holds the second place among the mountain chains of this continent. All our rivers of the first magnitude have their sources, either in the Rocky Mountains, or in elevated spurs, projecting from the sides of that range. The largest of the rivers, flowing from the Alleghanies, is the Ohio; and even this, running almost parallel to the range, and receiving as many, and, with a few exceptions, as large rivers from the north as from 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 descent towards the Atlantic is at least {6} 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 Mississippi Valley. If we consider attentively that extensive portion 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 hereafter particularly described, running from near the north-western 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 argillaceous sandstone, compact limestone, and other secondary rocks. Though these rocks extend almost to the highest summits of the Alleghanies, and retain even there the horizontal position which they have in the plains, the region they underlay is not to be considered as forming a district 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 direction 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,