increase in the number of pipes being made on account of the valley being deeper than that of the Garon, and, as he thinks, as the pressure increases, while the depth is

augmented, that the architects multiplied the number of syphons, to divide this force by diminishing their diameter in proportion a circumstance which, if accurate, would clearly decide that the difference between the weight and the pressure of water, was unknown to the Roman architect. The rest of the syphon bridges are similar to that of the Garon. There is now no vestige of the emitting reservoir of St. Foi. The receiving reservoir of St. Irenaeus is also much dilapidated, and also that of Soncieu. Delorme conjectured that its side was pierced for a smaller number of syphons than that of Soncieu but these pipes were of a greater diameter than those of the others, as appears ;

by the parts at present in existence and Delorme thinks that the emitting reservoir was ;

like the receiving tanks, which are seen near the wall of the city of Lyons, and conducted

the water by an aqueduct to the reservoir, now called the Maison Angclique, This reservoir was also furnished with the usual opening. The emitting reservoirs had an opening at a height of four and a half feet above the level of the pavement, to turn, if required, the flowing water to the bottom of the tower, and to facilitate their cleanings and reparations. The great reservoir of the Maison Angelique, the bottom of which is now buried in the ground, was supported by a series of vaults, separated by partition walls two and a half feet thick. Five of these vaults are still entire. They are semi-circular, built of small, rough, square stones, with courses of bricks in the voussoirs, in each ten and a half inches, and they appear to have been laid without mortar.