Bridges were sometimes erected by private munificence• like the charming one at Chamas, in France (single span of 41 feet. length 53 feet) ; or by the eo6perative contributions of communes, like that of Alcantara, in Spain, built by Lacer in 105. and consisting of six granite arches 600 feet long, 26 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 nman bridges, as is seen on many coins; for Pie, cm the bridge at Antioch and on that at nesia; at the Mulvian and Fabrician bridges, Martorell, and many others. 'Tice bridge at Saint-Chamas still shows. in a modest way, its two arches intact. Roman bridges, too numerous to enumerate, are scattered every where. The Roman arched viaducts spanning valleys and carrying the water-supply, such as the 'Pont du Gard,' in France, those of Segovia and Tarragona. in Spain, and of Carthage, arc discussed under AQUEDUCTS.
The care of the bridges was intrusted during the Roman rule to the curatores viarum, under an administration superbly organized, with spe cial budget ; and in the frontier provinces they were under military control. Bridges remained a matter of prime importance, as military move ments and efficient taxation depended upon the maintenance of communications. So even at tire time when Italy had been devastated by the wars of the Fifth and Sixth centuries, Narses still prides himself on his restoration of a bridge near Rome. The Lombard and Frankish rulers, had great difficulty in maintaining any efficiency in the matter of preservation of bridges. Charle magne and his successors laid the duty upon the local bishop, as well as the imperial commission er. and as the duties were collected at the bridges it is to be supposed that every effort was made to keep them intact, but with indifferent success, owing to the lack of engineering ability in West ern Christendom.
Considerin_ now the history of ancient bridge building in the Orient, the earliest specimens extant would appear to be two in Persia, at Dizful and Shuster, belonging to the late :kelt:1. 111mM] kings, though they may not be earlier than some of the Roman bridges; they are interesting as having the wide pointed arches that became so characteristic of :Mohammedan architecture. The network of Roman roads throughout Asia Minor and Syria, with their magnificent bridges (e.g. at Apamea ) , was maintained in good condi tion by the Byzantine rulers, and new ones were erected, witness that near Adabazar, built in 561 by Justinian, 1400 feet long, with S arches of 75 feet span; that at Adana in Cilieia, with 18 arches on enormous piers, and that at Mopsues tin with 9 arches—both erected by Justinian.
The Arabs continued this tradition by utilizing the services of both Persian and Greek engineers, and continuing the service of military roads. with regular stations for relays and the accommoda tion of travelers (see CARAVANSERAI ) . There were great bridges at Cordova (A.D. 717). at llama (11amath) with 11 arches. Antioch with 4 arches, near Aleppo with 13 arches, Adana, Aspenilos. Beirut, with 7 arches, and many other places. As was the ease in Spain, the care of the Ilyzantine and Mohammedan rulers and the continuity of their civilization insured the preser vat hal of the Roman bridges and the creation of new ones of monumental design, while in Eu rope the old traditions had been lost for nearly six centuries. Sultan Beybars, for example, was a great bridge-builder in Syria and Egypt, as at Lydda and Dania.
With the revival of arehileetural and engineer ing skill in the Eleventh and Twelfth centuries in Europe, and the contemporary development of great cities, bridge-building awoke to new life throughout Europe. Broad rivers, heretofore crossed by ferries, were successfully bridged. Bridges on the outskirts of cities were strongly fortified. with high towers at the ends and some time in the centre, like tire Valenta. Bridge at Cahors. The media'vai bridges were generally more steeply graded than the Roman. A small but very picturesque example of a very steeply graded bridge is near the Baths of Lucca (Tus cany), hence called 'Polite del Diavolo.' Some had two passageways, and a few, like that at Croyland, had three. This strueture, \villa is one of the most curious of the early bridges, is known as the 'Trinity Bridge,' and is supposed to have been built about 1380 by the Abbot of Croyland in Lincolnshire. II stands at a point where the main stream of the river Welland di vides into two branches. and the three arches provide for three watercourses and three road ways. Strictly speaking, the bridge consists of three half arches rising from the apexes of an equilateral triangle and meeting at a vonnnou point over the centre of the triangle. Owing to the steepness of its roadway. this bridge could never have been used for vehicles.