But by far the most remarkable feature of the Ohio valley is, that its real slope does not correspond to the courses of its rivers. It is a fact now well known, that load ed boats at high water can pass from Lake Michigan into Illinois river, and vice versa. We have seen that Lake Elie was 565 feet above the level of the Atlantic tides. The elevation of Lake Michigan above Lake Erie can not, from the shortness and gentle currents of Detroit river, St. Clair river, and the straits of Michilimachinak, exceed 35 feet. We may therefore assume 600 feet as the level of Lake Michigan. This would correspond very nearly with that of the Ohio river, between the mouths of Miami and Kentucky rivers. Illinois river we will see, presents much more the aspect of a canal than that of a river, whilst the central table land we have re viewed, is so elevated, as to produce water-courses, whose descent is rapid, and those flowing into Lake Eric all precipitated over falls before reaching their recipient. During the continuance of spring floods, loaded boats of large tonnage may be navigated from the rapids of Ohio, by that river, the Mississippi and Illinois rivers, and through the Canadian sea to the cataract of Niagara, without meeting a single rapid ; whilst the direct line between the extremes of this navigation, would pass over an elevated ridge. When due attention is paid to the real phenomena of the connected basins of 'Missis sippi and St. Lawrence, the true causes of the apparent anomalies we have noticed are developed. It is at once rendered apparent, that the true slope of the Ohio valley is nearly at right angles to the range of the Appalachian mountains, and that its lowest line of depression, is the channels of the Illinois and Mississippi rivers.
Soil, climate, and productions.—The soil of this in teresting section of the earth, is by no means so uniform as is generally supposed, though taken as a whole, may be considered fertile. The alluvial bottoms of the streams, great and small, are generally a deep loam, ex uberantly productive. This rich vegetable earth, in many places reaches the apex of the highest hills. Those hills present, however, great variety of soil ; always clothed with timber, though often precipitous, rocky, and sterile. The extreme south-eastern part, from the sources of Allegany to the most southern part of the valley in the state of Alabama, presents a mountainous or very broken hilly tract of country, upwards of 700 miles in length, with a mean width of about 100. The soil is on this region extremely varied, and as it contains at its extremities nearly the greatest contrast of latitude of the valley of which it forms a part, the vegetable pro ductions, natural and artificial, are here also most varied. Very few timber trees, known on this continent between N. Lat. 34 and 42 degrees, but which are here found. The most prominent and valuable species of which, are ten or twelve species of oak ; hemlock, pine, the Lirio dendron tulipifera ; five or six species of hickory and walnut ; three species of maple, one of which, the Acer saccharinum, is amongst the most singular and valuable trees known on this globe ; three or four species of ash, with an immense variety of useful trees and shrubs not enumerated. The Flora is also highly varied and ele
gant. Medicinal plants abound. Spring water is abun dant and excellent.
Of naturalized plants, trees, and shrubs, the number and variety preclude a complete specification. Extend ing through eight degrees of latitude, and presenting considerable difference of level, the climates admit the cultivation of plants whose powers of resisting the in clemencies, or of profiting by the changes of seasons, are very different. The cereal gramina—wheat, rye, oats, barley, and Indian corn or maize, is every where cultivated. Meadow grasses flourish best in an advance to the north. In the southern part, even where exten sive settlements have been made, meadows are rare ; but towards the northward, form a large part of rural economy. This observation, though in a more limited extent, may be applied to orchards, and even gardens. Where the crops become very valuable, horticulture is every where neglected, as are orchards, except in the vicinity of cities or large towns. In the region before us, below N. Lat. 36° 30', cotton commences to be culti vated as a valuable crop. Some culture of this vege table extends north of the assumed limit, but rather for domestic use than as an article of commerce. The quantity and quality of this vegetable is enhanced, sail and exposure being equal, in a very near ratio, with advance to the south. As we will have more occasion to dilate on this vegetable in the sequel of this article, it would be irrelevant to touch farther on the subject in this place.
The orchard trees generally cultivated in the region before us, are the apple, pear, peach, plum, nectarine, &c.
The mineral treasures of this region compose a large share of its most valuable productions. Iron, salt, and mineral coal, are the most valuable and abundant. Iron ore is found in almost every section of this extensive line. The immense masses of mineral coal are very extensive: those near Pittsburg are only the most abundant and best known. It is amongst the most remarkable features in the natural history of the United States, that from Onon dago in the state of New-York, to the south-west angle of Virginia, the earth appears in every place, at certain depth, to afford water saturated with muriate of soda, (common salt.) This indispensable mineral is found where, if wanting, it could not be obtained without very great expense. Salt is now made at Ononddgo in Neu-York, Conemaugh in Pennsylvania, and on the Kenhawa and other places in Virginia ;—all in the same range.