BBIDGE 176 BRIDGE work. Spars, ropes, and planks are used in a variety of ways for spanning narrow chasms. The pontoon bridge is the only one which is carried with an army. Heavy guns are better warped across on specially constructed rafts. A flying bridge is a boat or raft anchored by a long cable up stream, and carried across by the action of the current acting obliquely against its side, which should be kept at about an angle of 55° with the current. Of the rock formations called natural bridges, the most remarkable is the countries of imperfect civilization even yet they are few. Following is a list of the notajble bridges of the world: Pons Sublicus, across the Tiber at Rome, defended 507 B. C, by Horatius Codes. Caesar's bridge across the Rhine, a wooden trestle-work, built 55 B. c. Trajan's magnificent bridge over the Danube, 4,770 feet in length, built A. D. 115. London bridge. One existed at the end of the 10th century; one built of wood, LARIMER BRIDGE, PITTSBURGH, PA. — A CONCRETE ARCH natural bridge over Cedar Creek, in Vir- ginia, 125 miles W. of Richmond. The mass of siliceous limestone through which the little river passes is presumably all that remains of a once extensive stratum. The cavern or arch is 200 feet high and 60 feet wide. The solid rock walls are nearly perpendicular, and the crown of the arch is 40 feet thick. History of Bridges. — Bridges seem to have existed in China from a period of considerable antiquity. The word bridge does not occur in the Authorized Version of the Bible. Temporary bridges, for military purposes, were con- structed before permanent structures for the convenience of the inhabitants were erected. The former were often of boats. Thus, Cyrus constructed such bridges about 536 B. c, Darius Hystaspes about 490, and Xerxes about 480 B. C. Bridges of stone or brick seem to have been first used by the Romans; there were none erected in Greece till after the Roman conquest. The first Roman bridge is said to have been one spanning the Tiber, between the Janiculum and the Aventine mountain, built by or under Ancus Martius. Now they are universal in properly civilized countries, though in 1014; a stone bridge, by Peter of Cole- church, begun 1176, was finished 1209. The new London bridge is constructed of gn^anite, from the designs of L. Rennie; it was commenced in 1824 and completed in about seven years, at a cost of $7,290,000. The bridge at Burton, over the Trent, was formerly the longest bridge in Eng- land, being 1,545 feet. It is now partly removed. Built in the 12th century. The Bridge of the Holy Trinity, at Florence, Italy, was built in 1569. It is 322 feet long, constructed of white marble, and stands unrivaled as a work of art. The Rialto, at Venice, is said to have been built from the designs of Michael Angelo. It is a single marble arch, 98% feet long, and was completed in 1591. The Bridge of Sighs, at Venice, over which condemned prisoners were trans- ported from the Hall of Judgment to the place of execution, was built in 1589. Brooklyn Bridge was commenced, under the direction of John A. Roebling, in 1870, and completed in about 13 years. Coalbrookdale bridge, England, was the first cast-iron bridge. It was built over the Severn in 1779.
