Page:Encyclopædia Britannica, Ninth Edition, v. 4.djvu/373

EXAMPLES.] BRIDGES 329 de. la charpenterie) from the descriptions given in the his torians. This was the bridge defended by lloratias Codes. Plan at Pier. FIG. 102. Bridge thrown across the Rhine by Julius Ctesar. Fig. 102, also taken from the work of Colonel Emy, is in tended to represent the design of the bridge thrown across the Rhine in ten days by Julius Czesar (De Sell. Gall. iv. 17), Fia. 103. Pons Milvius. The Pons Milvius (fig. 103), now Ponte Molle, was built a mile and a half from Koine by the Censor ^Elius Scaurus, about 100 B.C. Some part of the first bridge is supposed to remain, although it has been altered from time to time. The arches vary in their opening from 51 feet to 79 feet 9 inches; the waterway between the piers is 413 feet 3 inches ; the breadth of the bridge, 28 feet 9 inches ; these dimensions are given on the authority of Cresy (Encyclo paedia of Civil Engineering). The following bridges also crossed the Tiber at Rome : The Pons Palat lints, which stood on the site of the present Ponte Rotto ; the Pons Fabricim and Pons Ccstius, which still remain ; the Pons Janiculanus, which occupied the site of the modern Poute Sisto; the Pons Vaticamis, which has disappeared; and the Pons jElius, built by Hadrian (13 A.D.), now the bridge of St Angelo. This bridge (fig. 104) was repaired by Popes Nicholas III. and Clement IX. The largest arch has a span of 62 feet 4 inches, and the width of the bridge is 50 feet 9 inches. The bridge erected by Trajan (104 A.D.) across the Tons Other Roman Trajan s Bridge. Cross Section. Elevation. Fro. 101. Bridge of S. An<?elo. Danube, just below the rapids of _the Iron Gate, has been the subject of much controversy. The drawing (fig. 105) was originally taken from a bas-relief on the Trajan column at Rome. A description of the bridge is given by the ancient historian Dion Cassius, who states that the bridge had twenty piers of hewn stone, 150 feet high and GO feet wide, with openings between them of 170 feet, spanned by arches. Doubt has been thrown on the accuracy of this description, because the design shown in fig. 105 is obviously unsuited to a span of 170 feet; nevertheless thirteen piers are still visible out of the twenty, according Fia. 105. Tiajan s Bridge, to Murray s Handbook The writer has not been able to lind any accurate measurement of the width between these piers, but as t-ic Handbook speaks of the length of the bridge as perhaps 3900 feet, and as the Conte Marsigli, writing from personal observation, in a letter to MoUtfaucon, gives the total length as probably 3010 feet, there can be no doubt that the spans were very considerable, and that the representation of the design in the bas-relief is almost wholly conventional. The one point as to which it gives clear information, not supplied elsewhere, is that tile superstructure was of wood. The piers seem to have been founded by sinking caissons. Murray s Handbook gives the depth of the river as 18 feet. Apollodorus of Damascus was the architect of this remarkable bridge. The bridge at Rimini. Rimini, built during the reign of Augustus, was especially admired by Palladio (Rondelet, L Art de batir). The bridge at Narni, on the road from Loretto to Rome, also Kami, built by Augustus (Montfaucon), and the bridge of Alcantara over the Tagus, built in the reign of the Emperor Alcantara. Trajan, are often cited as remarkable works. The Romans frequently adorned their bridges with a triumphal arch. A small example of this kind of bridge at St Chamas, in France, is shown in fig. 106 (Cresy s En- st Cliamns. cyclopaedia of Civil Engineering}. The span of the arch is 42 feet, and the voussoirs are 3 feet 5 inches deep. Fig. 107 shows the bridge of Narses, built in the 6th century, route and which carried the Via Salaria across the Anio or Sahro.

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