How little reason there is to ascribe to extraordinary convulsions the excavations which are made by water upon the surface of the earth, will appear most evidently from the examination of that natural bridge of which mention is made above, and which is situated in the same ridge of mountains, far to the south, upon a branch of James's River. Mr Jefferson gives the following account of it. "The natural bridge, the most sublime of nature's works, is on the ascent of a hill, which seems to have been cloven through its length by some great convulsion. The fissure, just at the bridge, is by some admeasurements 270 feet deep, by others 205; it is about 45 feet wide at the bottom, and 90 feet at the top; this of course determines the length of the bridge, and its height from the water. Its breadth in the middle is about 60 feet, but more at the ends; and the thickness of the mass at the summit of the arch about 40 feet. A part of its thickness is constituted by a coat of earth, which gives growth to many large trees. The residue, with the hill on both sides, is one solid rock of lime-stone. The arch approaches the semi-elliptical form; but the larger axis of the ellipsis, which would be the cord of the arch, is many times longer than the transverse. Though the sides of the bridge are provided in some parts with a parapet of fixed rock, yet few men have resolution to walk to them, and look over into the abyss. You involuntarily fall on your hands and feet, and creep to the parapet, and look over it. Looking down from this height about a minute gave me a violent headache. If the view from the top be painful and intolerable, that from below is delightful in the extreme. It is impossible for the emotions arising from the sublime to be felt beyond what they are here. On the sight of so beautiful an arch, so elevated, so light, and springing as it were up to heaven, the rapture of the spectator is really indescribable! The fissure, continuing narrow, deep, and straight, for a considerable distance above and below the bridge, opens a short but very pleasing view of the north mountain on one side, and blue ridge on the other, at the distance each of them of about five miles. This bridge is in the county of Rockbridge, to which it has given name, and affords a public and commodious passage over a valley, which cannot be crossed elsewhere for a considerable distance. The stream passing under it is called Cedar Creek: it is a water of James's River, and sufficient in the driest seasons to turn a grist mill, though its fountain is not more than two miles above[24]." [Footnote 24: Upon this occasion it may be observed, the most wonderful thing, with regard to cosmology, is that such remnants, forming bridges, are so rare; this therefore must be an extraordinary piece of solid rock, or some very peculiar circumstances must have concurred to preserve this monument of the former situation of things.]