Page:The New International Encyclopædia 1st ed. v. 03.djvu/546

* BRIDGE. 480 BRIDGE. em bridges may be cla.isificd as: (1) Arch bridges, (a) masonry and (b) metal; (2) girder bridges, (a) plate girders and (b) braued gird- ers or trusses: (.■?) suspension bridges; (4) draw bridges. The.se and sui)plementarj' head- ings will be used in this article. ANCIENT AND MEni.EVAL BRIDGES. It is thought that probably the Chinese first employed the masonry arch for bridging streams. All that is known, however, is that bridges and other public works were e.Kecuted in China B.C. 2000, and that arch bridges of evidently very gieat age are found in different parts of the Empire, some of which arc excellent examples of masonry arch construction. As no bridges have survived from ancient Egypt, which had little use for them, or from Babylonia or .Assyria, where they were never attempted on a large or permanent scale, the earliest remaining examples, apart from China, appear to belong to that interesting group of 'Hittite' and 'Pelasgic' tribes that peo- pled the shores and islands of the Mediterranean in prehistoric times. The Cretans, many of whose cities are known to be of earlier founda- tion than Troy, Tiryns, or Mycense. in their pos- sessions in Asia Minor, Syria, Greece. Italy, and the adjoining islands, connected theircities with a network of macadamized roads requiring bridges. and their work shows that they were skillful engineers. The earliest examples are built with immense abutments and piers of polygonal ma- sonry, connected by wooden planks, like the later one across the Euripus in Eubcea. Then the blocks of the piers were ovcrlning so as finally to meet in an almost triangular false pointed arch, like the gallery at Tiryns and the gate at Arpi- num. Tliis was the case at Metuxidi. and across the Pamisus, in Messenia. as well as in a bridge near Sparta. Other early bridges, all of stone, exist near Myceme and Phlius. Finally, for nar- row rivers, the end piers were connected by true voussoired round arches. This stage was not reached until the Seventh or Sixth Centurj- B.C. in Italy, as is shown by the bridges at Bieda, Cora, and Vulci, and was probably never known in Greece, where the arch was not developed, even for engineering purposes. Wiat the usual Greek method was in historic times is probably showii by the bridge at Assos, where the stone piers are connected by parallel stone lintels, dow- eled together. First the Etruscans, and then the Romans, in- herited and developed the engineering ability of the 'Pelasgic' tribes. As soon as the building of the Via Appia had initiated, in the Fourth Cen- tury B.C., the policy of binding the possessions of Rome together by great nuicadaniized roads, the Romans entered upon an uirivaled career of bridge and viaduct construction, which has fur- nished models for all succeeding ages until the modem invention of the metal bridge. As in all their public structures, the Romans made their bridges far more monumental and artistic than necessity required. Some of the Republican period remain. The Ponte T^upo and other mag- nificent bridges and viaducts for the Anio Vetua aqueduct (n.c. 144-140) are great stone arches of tufa and travertine; so is the viaduct near Gabii (Ponte di Nona), probably built in n.c. 124-121, with seven arches, and 28.5 feet long, still in use. In Rome itself the .Emilian Hridgc, in B.C. 179-142, is said to have been the first stone bridge to span the Tiber, all previous bridges having been of wood; and until quite a late date wooden bridges continued in use, especially for wide rivers. Then came the Fabrician Uridge, in B.C. 62, with two round arches, built, like the rest in Rome, of peperino and tufa, faced with mas- sive blocks of travertine, and the only one of these ancient bridges that has remained intjict. 'I he -Lilian Bridge, or "Ponte Sanf Angelo,' built by Hadrian in A.n. 130, with eight arches, was the most suj^rb of all, and remains in great part. It was almost rivaled by the later "Ponte Sisto' of Valentinian. These bridges had a considerable upward grade toward the centre, which added to their architectural effectiveness. The great roads radiating from Rome like the spokes of a wheel, such as the Via Salaria (Ponte Salaro), Appia, .uielia. Flaniinia, Valeria. La- tina. Cassia, .Emilia, recjuired a number of bridges. The Flaniinia, commencing at the great Mulvian Bridge, built in n.c. lOlt. was construct- ed by Augustus with all its bridges; that at the further end of the road, at Ariminium (Rimini), is the best preserved, with its five great arches and length of 23G feet. Other Augustan bridges, in ruins, are near Borghetto and Xarni ; and, in the north, near Aosta, Calzi, etc. The great one at Verona is rebuilt, as is that of Vicenza. The spread of Roman dominion to Spain, Gaul, Af- rica, Greece, Asia Minor. Sjria, the Danubian lands, Orniany, Britain, meant everywhere the building of great military roads with permanent bridges b_v the Roman legions, under the direction of their military engineers. The most colossal was the bridge over the Danube, built in A.u. 102 and 103 by Apollodorus. the greatest architect and engineer of his time, for Trajan, to enable the Emperor to conquer Dacia. The stone piers still stand; its superstructure was of wood. Previous bridges of such enormous length had been temporary and on boats. Throughout the countries that had been included in the western provinces of the Emi)ire so little care of the bridges was taken in the Dark Ages that few have survived. In France are those near Chilteau- neuf, Vaison, and Saint-Chamas, and the founda- tions of many more. The Spanish Peninsula is the great exception. Its bridges were among the most superb pieces of Ronutn engineering, .and the high culture of the Moors insured their i)res- ervation. The best examples are at Martorell, Cuenea, Evora, Alconetar. Cordova, Merida, A- cflntara, (^'liaves, Orense, Olloniego, Ona, Alina- zan, !ind especially the superb example at Sala- manca, built, like so many of the others, by Trajan. Bridges were sometimes erected by private munificence, like the charming one at Saint Chainas. in France (single span of 41 feet, length 83 feet) ; or by the coiiperative contributions of communes, like that of Alci'intara, in Spain, built by I.,acer in 105, and consisting of six granite arches GOO feet long, 20 feet wide, and 45 feet above the normal level of the Tagus — a superb structure still standing. Originally there stood triumphal and memorial arches at one or both ends or in the centre of the most important Ro- man bridges, as is seen on many coins; for exam- ple, on the bridge at Antioch and on that at Mag- nesia; at the .Mulvian and Fabrician bridges, AlcJintara, Martorell, and many others. The bridge at Saint-C'hamas still shows, in a modest wav. its two arches intact. Roman bridges, too