We cannot put a date on this Roman masterpiece, because in this matter there are differences of opinion. M. Ménard, historian of Nîmes, attributes the work to Agrippa, son-in-law of Augustus, who is said to have ordered its construction about nineteen years before the Birth of Christ. The architecture belongs to the Tuscan order. Its vaults are semicircular, and spring from ledges, or imposts, about 50 centimetres high, and as much in projection. There are four parallel rings of stone in the vaults of the first tier, and three in the second, while the third tier has either one or two. This Roman method of building the under surface of an arch, by laying stones in parallel bands or rings, side by side, but not bonded together, was copied in the Middle Ages (p. 82). One point more: the water channel of the aqueduct, placed on top of the third arcade, is 1 m. 30 cm. wide and 1 m. 60 cm. high; it is nearly blocked up with a thick deposit of lime, but when this substance is detached we find on the side walls a deep layer of cement coloured red. The bed of this channel is a solid floor, 22 cm. in thickness, and its component parts are small pebbles mixed with lime and gritty sand. Like other antique monuments, the Pont du Gard has been ravaged by the brutality of mankind. At the end of the seventeenth century, for instance, during years of religious warfare, so called, the Pont du Gard was often crowded with fugitives and with troops, who made a footway for themselves along the upstream side above the first arcade by means of a strong platform corbelled out from new imposts. Over this road cavalry and artillery passed at full speed, not only shaking the bridge, but causing the topmost tier to develop a curve which is still noticeable. At last the province of Languedoc interfered, and in 1670 careful restoration was begun. Years later, in 1743, the _états généraux_ decided that a good highway should be built up against the eastern side of the Pont du Gard; and this new bridge, finished in 1747, was perhaps justified by its utility, though it harmed a classic monument. There have been a good many modern restorations, and one day the aqueduct itself may be brought into use again, in accordance with the wishes expressed by a great many persons.[68] II