BRIDGE, a structure of wood, stone, brick, iron, or other material, raised over it river, pond, lake, or any intervening space, for the purpose of a convenient mode of passage for men or animals. The extreme supports of a bridge are called the butmcnt$, or abutments. See ABUTMENT. If composed of more than one opening, the intermediate sup porters are called piers : the protecting walls or fences on each side are called parapets.
When the bridge is intended for both foot-passengers and carriages, the sides are generally raised, and sometimes paved with flag-stones, and are called banquettes, or ; the middle part, being reserved for carriages, is the road, or In tills place we propose to give a slight historical sketch of the rise, pi- gross, and present state of bridge-building, exemplified in descriptions of the most celebrated edifices of the kind in various parts of the world. Under the respective heads of STONE BRIDGE, TIMBER BRIDGE, IRON BRIDGE, SUSPENSION BRIDOE, &e., will be found the required infbr Illation on each of these several branches of this important subject; and some account will be given of the theory under STONE BRIDGE.
The origin of bridges, there can be no doubt, takes its date very far back in the annals of the human race, though we have no documents by which to trace their progressive improvement, from the trunk of a tree, rudely thrown by accident or choice over a stream, to the convenient and stu pendous edifices of more modern times.
It is probable that the first bridges were composed of lintels of wood or stone, stretching from bank to bank ; or if the breadth of the river or valley to be passed N•ere Con side•able, resting on piers or posts fixed in the bed of the river. In a strong current, the frequent piers or posts required for the support of lintels, would, by contracting the water-way, increase it to a torrent, obstructive of navigation, and ruinous to the piers themselves. In constructing bridges therefore over rapid rivers, it would be found essential to their stability, that the opening; between the supporters should be as wide as possible, and every facility given to the free passage of the water ; and as this could be effected only by the use of stone arches or wood trusses, there can be no doubt that these inventions were perfected before bridges of importance had become common.
There are still remaining bridges of great antiquity built by the Romans, but we are not acquainted with the earliest history of so useful a contrivance. It is by many supposed that the Greeks very soon adopted the use of arches, but at any rate they do not appear to have applied them to other purposes than for covering apertures in their buildings. See ARCM, ARCHITECCCURE. Nor had they a bridge over the Cephisus, which crossed the high-road between Athens and Eleusis, till the Emperor Adrian erected one. In the Old Testament there is no mention of a bridge, and perhaps the bridge of Semiramis, at Babylon, may be considered the oldest on record.
The Chinese lay claim to a high antiquity for their skill in bridge-building by means of arches. Several of these structures are of great magnitude, built of stone, and turned on arches in the usual manner ; others are constructed with stones from five to ten feet in length, so cut as each to form the segment of an arc, which consequently has no key-stone; ribs of wood being fitted to the convexity of the arch, and bolted through the stones by iron bars, fastened in the solid parts of the bridge.
The suspension-bridges of South America are of a very extraordinary character, and from the lightness of their mate rials, their oscillation, and the great height at which they are sometimes suspended, present to the startled traveller objects at once alarming and picturesque, and well calculated to try the strongest nerve. See SU5PENSION-13RIDGE.
The Roman bridges are described by Bergier, as possessing all the requisites met with in a modern bridge; they consisted of piers, arches, butments, carriage-ways, and raised ban quettes or footpaths separated from the road by a railing, and sometimes furnished with a cover to shelter passengers from the weather. Their solidity and proportion prove they must have been constructed on sound principles.