160

HISTORY OF ENGINEERING.

Book 1.

The character of the architecture is the best met with in Gaul ; the stone wasbrought from the neighbouring quarries of Hassissane, anil the courses are regularly laidand jointed.

Fig. 178. BRIDGE AT ST. CIIAMAS

The span of the arch is 42 feet, and measured on the soffite its breadth is 19 feet 9 inches ;there are 39 voussoirs, 3 feet 5 inches in depth j on each side one projects 13 inches, tosupport the centre.

The clear width of the roadway between the parapets is 15 feet 6 inches, and the lengthbetween the triumphal arches at each extremity 74 feet 9 inches.

The opening of each of the triumphal arches is 11 feet 8 inches, and the height to thespringing 9 feet 4 inches; the total height to the top of the cornice 23 feet, and the entirewidth, as measured along the frieze, 24 feet, forming nearly a square.

Fig. 179.

BRIDGE AT ST. CIIAMAS.

The writer in 1817 found this beautiful bridge as perfect as here represented. Some ofthe stones had been repaired, and a few of the upper courses had smaller introduced; basedupon a rock, and constructed with the greatest care, it promises to remain as many centuriesas it has already done, a monument of the taste and skill of Roman engineers. Palladioand other architects have designed bridges with triumphal arches and covered ways, in