Nismes, and who, by this means, endeavored to force the citizens to surrender. It remained in this state until the beginning of the eighteenth century, when the Duke de Rohan, in order to make a passage for his artillery, perforated the piers of the second arcade, and by some other operations directed to the same end, the Pont du Garde was rapidly falling to pieces. Considerable rents in the walls, and deviations from the perpendicular, exciting public attention, the provincial States took the matter into consideration, and by a series of judicious repairs, they succeeded in restoring this ornament of Languedoc to the state in which it was, before the dilapidations of the Due de Rohan. In 1746, the project of building a bridge near the site of this aqueduct was, fortunately for its further stability, modified so as to be built adjoining to it. M. Petot proposed to form this bridge on the eastern face of the Pont du Garde, and rigorously following the 32 PRELIMINARY ESSAY. dimensions of the piers and arcades of the ancient aqueduct, this was shortly afterwards erected. Aqueduct at Lyons. Nothing gives us a higher idea of the ancient splendor of the city of Lyons (Lugdunum,) under the emperors, than the remains of its ancient buildings, temples, palaces, amphitheatres, naumachias, baths, and, above all, its aqueducts, erected during the reigns of Augustus, Tiberius, and Claudius, to supply that part of the city with water, which was situated on the heights. The oldest, that erected by the troops of Marcus Antoninus, drew its waters by two branches, from the group of hills, called in modern times, Mont d'Or : this stream having been found inadequate for the proper supply of even the highest division of the city, a second aqueduct was constructed, which drew its water from the Loire. The third aqueduct was formed under, to conduct water to the highest part of the city, on which was erected the palace built by the Emperor Claudius. Remains of other minor aqueducts, built in the same age, are of the same construction, the arches and parts apparent being of the masonry called by the ancients opus reticulatum. A fourth aqueduct, formed along the bank of the Rhone, appears to have been the source from which the lower city received its supply of water ; and from its remains there is little question but that it . also was constructed by the Romans. The Claudian aqueduct, being that which has most attracted the attention of antiquaries, will be described more in detail. The body of the work, that is, the arcades that carried the aqueduct across the valleys, is built of masses of rubble stone and cement, faced, as has been stated, with the opus reticulatum. In this instance, this kind of work is supposed to have been formed by laying a bottom of brick, of two, three, or four layers, then a caisson of wooden sides was applied to it,- and fixed thereon. The caisson was first lined with the squared stones which were to form the face ; the middle was then filled with rubble stones, into which a liquid cement of lime, fine gravel, and water, beaten up to a perfect degree of incorpora- tion in its liquidness, so as to become a binding cement, was poured, and in that state entered into every interstice of the rubble work. This operation being repeated, the whole was wrought into one incrusted rock, harder than either of the materials themselves separately were. One can conceive, says a learned antiquary, how a careful beating together of these materials had the effect of creating so binding a cement, since we know from our own practice, that puddling earth, fine gravel, and water together, form a lining for a canal, that becomes impervious to water when once settled, and it was probably from this puddling, and not from any secret as to the materials of the mortar, not now known, that this ancient cement owed its cohesive strength. When this square was set, the sides of the caisson were taken off, and another layer of bricks was then laid, and so Another caisson, and so on. The bricks used in this construction were one foot nine inches PRELIMINARY ESSAY. 33 long, one foot broad, and one and a half inches thick ; the cement of one of the aqueducts at the bottom is six inches thick, and one and a half thick on the sides ; about two feet above the floor of the canal were fixed, on each side, cramps of three lines square, at two and a half feet distance from each other. The utmost breadth of the piers of the aque- duct of Chaponost, which carried a canal of three feet broad, by six feet high,