The American Cyclopædia (1879)/Bridge, Natural
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|Edition of 1879. See also Natural arch on Wikipedia, and the disclaimer.|
BRIDGE, Natural. I. In Rockbridge co., Virginia, 115 m. W. of Richmond, and 160 m. S. W. of Washington. It is distant by stage road from Lexington, the capital of the county, 14 m.; is 30 m. from Bonsack's, the nearest station on the Virginia and Tennessee railroad, and 36 m. by canal boat from Lynchburg. It is situated at the extremity of the deep chasm in which flows the little stream called Cedar creek, across the top of which, from brink to brink, there extends an enormous rocky stratum, fashioned into a graceful arch.
The bed of the stream is more than 200 ft. below the surface of the plain, and the sides of the chasm, at the bottom of which the water flows, are composed of solid rock, maintaining a position almost perpendicular. The walls do not seem to be water-worn, but suggest the idea of an enormous cavern, that in remote ages may have been covered for miles by the continuation of that stratum of which all that now remains is the arch of the natural bridge. A plumb line dropped from its centre down the vertical face of the rocks swings clear at the depth of 40 ft., which is the thickness of the crown of the arch. Toward its sides this regularly increases with a graceful curve, as in an artificial structure. Its breadth is full 60 ft., and the stone is a highly silicious limestone, extremely hard to break, formed in massive blocks and strata, with no evidence upon its weathered surface of a tendency to decompose and crumble away. It is thus apparent that the insignificant little stream which now runs in this deep gorge has had no agency in shaping and producing this wonderful channel. Mightier forces have worn away the hard strata, more powerful torrents than any that now flow over the surface set in motion probably when this portion of Virginia was shaken by those great convulsions which displaced its piles of strata to the depth of thousands of feet, bringing into juxtaposition, along the line of fissures which are still to be traced, groups of rock everywhere else found separated by other formations, the aggregate thickness of which might be measured by miles. The mineral springs so common in this region, and particularly along the lines of these disturbances, flow up from great depths, as is made evident by the high temperature of many of them. Across the top passes a public road, and being in the same plane with the neighboring country, one may cross it in a coach without being aware of the interesting pass. There are several forest trees of large dimensions growing near the edge of the creek directly under the arch, which do not nearly reach its lowest part. The most imposing view is from about 60 yards below the bridge, close to the edge of the creek; from that position the arch appears thinner, lighter, and loftier. A little above the bridge, on the western side of the creek, the wall of the rock is broken into buttress-like masses, which rise almost perpendicularly to a height of nearly 250 ft., terminating in separate pinnacles which overlook the bridge. On the abutments of the bridge there are many names carved in the rock of persons who have climbed as high as they dared on the face of the precipice. Highest of all for nearly three quarters of a century was that of George Washington, who when a youth ascended to a point never before reached, but which was subsequently surpassed in 1818 by James Piper, a student in Washington college, who actually climbed from the foot to the top of the rock. II. In Walker co., Alabama, is a natural bridge said to rival that of Virginia. It is in the sandstone called millstone grit, which underlies the coal formation. It spans about 120 ft., and its height is about 70 ft. A smaller bridge connects it with the bluff beyond. The lines of stratification of the sandstone give the structure the appearance of having been artificially built up with massive blocks. It is in the midst of a region of wild and romantic beauty, high escarpments of the same sandstone being seen standing out in the face of the hills around. There is a similar bridge in Christian co., Kentucky, 130 ft. high, with a span of 70 ft. III. California has five natural bridges, the largest of which is on a small creek emptying into the Hay fork of the Trinity river, where a ledge of rock 3,000 ft. wide crosses the valley. Under this runs the creek, through an arch 20 ft. high by 80 ft. across. The rock above the arch is 150 ft. deep. On Lost river, in Siskiyou co., there are two natural bridges about 30 ft. apart. The rock is a conglomerate sandstone, and each bridge is from 10 to 15 ft. wide, while the distance across the stream is about 80 ft. One of these bridges is visited regularly by travellers. On Coyote creek, in Tuolumne co., 10 m. N. of Sonora, are two natural bridges, half a mile apart. The upper bridge is 285 ft. long with the course of the water, and 36 ft. high, with the rock 30 ft. deep over the water. The lower bridge is similar in size and height to the other.