On Wednesday the 5th of May, having completed some alterations, which it appeared necessary to make in our engine, and received on board all our stores, we left Pittsburgh and proceeded on our voyage. All the gentlemen of the party, except Dr. Baldwin, were in good health, and entered upon this enterprise in good spirits and with high expectations. Fourteen miles below Pittsburgh, we passed a steam-boat lying aground; we received and returned their salute, as is customary with the merchants' boats on the Ohio and Mississippi.
At evening we heard the cry of the whip-poor-will;[003] and among other birds saw the pelecanus carbo, several turkey vultures, and the tell-tale sand-piper. The spring was now rapidly advancing, the dense forests of the Ohio bottoms were unfolding their luxuriant foliage, and the scattered plantations assuming the cheering aspect of summer.
{5} A few weeks' residence at and near Pittsburgh, and several journies across the Alleghany mountains, in different parts, have afforded us the opportunity of collecting[pg045] a few observations relative to that important section of country, which contains the sources of the Ohio.
In the Alleghany river we found several of those little animals, which have been described as a species of Proteus, but which to us appear more properly to belong to the genus Triton. [004]
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[pg049] 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, or the north-east, until they at length acquire sufficient force to break through the opposing ridges, whence they afterward pursue a more direct course. As instances, we may mention the Monongahela river, which runs nearly parallel, but in an opposite direction, to the Ohio; the great Kenhawa, whose course above the falls forms an acute angle with the part below; also the Cumberland, and Tennessee, which run a {7} long distance parallel to each other, and to the Ohio. This fact seems to justify the inference, that some other agent than the rivers has been active in the production of the vallies between the subordinate ridges of the Alleghany. There appears some reason to believe that the rocky hills, along the immediate course of the Ohio and the larger western rivers, have received, at least, their present form from[pg050] the operation of streams of water. They do not, like the accessory ridges of the Alleghany, form high and continuous chains, apparently influencing the direction of rivers, but present groups of conic eminences separated by water-worn vallies, and having a sort of symmetric arrangement. The structure of these hills does not so much differ from that of the Alleghany mountains, as their form and position. The long chains of hills, which form the ascent to the Alleghany, on the western side, are based either on metalliferous limestone, or some of the inclined rocks belonging to the transition formation of Werner, and have their summits capped with the more recent secondary aggregates in strata without inclination, and greatly resembling those found in the plains west of the Ohio. It is not easy to conceive how these horizontal strata, unless originally continuous, should appear so similar at equal elevations in different hills, and hills separated by vallies of several miles in width. If that convulsion which produced the inclination of the strata, of the metalliferous limestone, the clay-slate, and the gray wacke, happened before the deposition of the compact limestone, and the argillaceous sandstones, why are not these later aggregates found principally in the vallies, where their integrant particles would be supposed most readily to have accumulated? On the other hand, if the secondary rocks had been deposited previous to that supposed change, how have their stratifications retained the original horizontal {8} position, while that of the transition strata has been changed?
Most of the rivers which descend from the western side of the Alleghany mountains are of inconsiderable magnitude,[pg051] and by no means remarkable, on account of the straightness of their course, or the rapidity of their currents. The maps accompanying this work, will, in the most satisfactory manner, illustrate the great contrast in this respect, between the district now under consideration and the eastern slope of the Rocky Mountains. The Tennessee, the Cumberland, the Kentucky, the Kenhawa and Alleghany rivers, though traversed in their courses by rocky dikes, sometimes compressing their beds into a narrow compass, occasioning rapids, and in other instances causing perpendicular falls, yet compared to the Platte, and the western tributaries of the Missouri generally, can be considered neither shoal nor rapid. Their immediate banks are permanent, often rocky, and the sloping beach covered with trees or shrubs, and the water, except in time of high floods, nearly transparent. The waters of the Ohio, and its tributaries, and perhaps of most other rivers, when they do not suspend such quantities of earthy matter as to destroy their transparency, reflect, from beneath their surface, a greenish colour. This colour has been thought to be, in some instances, occasioned by minute confervas, or other floating plants, or to result from the decomposition of decaying vegetable matter. That it depends on neither of these causes, however, is sufficiently manifest, for when seen by transmitted light, the green waters are usually transparent and colourless. Some rivers of Switzerland, and some of South America, which descend from lofty primitive mountains, consisting of rocks of the most flinty and indestructible composition, covered with perpetual snows, and almost destitute of organic beings, or exuviæ, either animal or {9} vegetable, and whose waters have a temperature, even in[pg052] summer, raised but a few degrees above the freezing point, which circumstance, together with the rapidity of their currents, render them unfit for the abode of vegetable life, and is incompatible with the existence of putrefaction, notwithstanding the transparency of their waters, and the reddish, or yellowish colour of the rocks which pave their beds, have a tinge of green, like the Ohio and Cumberland, at times of low water. It is well known that the water of the ocean, though more transparent than any other, is usually green near the shores; and on soundings, while at main ocean, its colour is blue. Perhaps the power which transparent waters have of decomposing the solar light, and reflecting principally the green rays, may have some dependence upon the depth of the stratum. If this were the case, we might expect all rivers, equally transparent and of equal depth, to reflect similar colours, which is not always the case.
In the southern part of Pennsylvania, the range called particularly the Alleghany ridge, is near the centre, and is most elevated of the group. Its summit divides the waters of the Susquehannah on the east from those of the Ohio on the west.
This mountain consists principally of argillite and the several varieties of grey wacke, grey wacke slate, and the other aggregates, which in transition formations usually intervene between the metalliferous limestone and the inclined sandstone. The strata have less inclination than in the Cove, Sideling, and South mountains, and other ridges east of the Alleghany. The summit is broad, and covered with heavy forests. Something of the fertility of the Mississippi valley seems to extend, in this direction, to the utmost limits of the secondary formation. The western[pg053] descent of the Alleghany ridge is more gradual than the eastern, and the inclination of the strata in some measure reversed. It is proper to remark, that, {10} throughout this group of mountains, much irregularity prevails in the direction as well as of the dip and inclination of strata. If any remark is generally applicable, it is, perhaps, that the inclination of the rocks is towards the most elevated summits in the vicinity.
Laurel ridge, the next in succession, is separated from the Alleghany by a wide valley. Its geological features are, in general, similar to those of the eastern ranges; but about its summit, the sandstones of the coal formation begin to appear alternating with narrow beds of bituminous clay-slate. Near the summit of this ridge, coal beds have been explored, and, at the time of our visit, coals were sold at the pits for ten cents per bushel. In actual elevation, the coal strata at the summit of Laurel-hill, fall but little below the summits of the Alleghany. Thus, in traversing from east to west the state of Pennsylvania, there is a constant but gradual ascent from the gneiss at Philadelphia, the several rocky strata occurring one above another, in the inverse order of their respective ages, the points most elevated being occupied by rocks of recent origin, abounding in the remains of animal and vegetable life.