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 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?