which more than sixty, in Delorme's time, were remaining. This was terminated by a reservoir, whence the water, in like manner as before, descended by pipes into another valley, and in part passed it and the river Baunan, over a bridge of a reversed curvature, and mounted again on the opposite side, there entering a second reservoir at St. Foi. The waters flowed hence in a canal, carried by a bridge for some way above ground, and then became subterraneous, and continued thus along the heights to the point near the gate of St. Irenseus. Here another reservoir was situated ; hence the waters flowed in leaden pipes, which descended into the fosse of St. Irenseus, and passing along the bottom of it, rose again, and emptied themselves in a reservoir, built near a spot which can be traced in the walls of the city, at the Mall of Fourviere, above the gate of Trion, on the south side of a square tower. These pipes were not carried across this ditch and valley upon a bridge, as has been stated by some authors ; there are not the least vestiges of such ; but they were bedded on a massive course of masonry. This aqueduct has a course of more than 13 leagues, or about 33 miles ; its distance in a right line, is about eight leagues, and its descent from the bridge of the little Varizelle to the Fourviere, is 360 feet. Delorme next describes the nature of these reservoirs placed on each side of those valleys, across which the waters were passed in syphons over a bridge of reversed curva- ture. The one is for holding up, or receiving, and thence emitting, the waters which are to be conveyed in pipes, and the other is to receive a sufficient quantity of water for dis- tribution to the succeeding canal. The emitting reservoir of the Garon aqueduct bridge is placed upon a quadrangular tower fourteen feet long, and four and a half feet broad. The wall of the side next the valley, is pierced at nine feet above the bottom of the reservoir, with nine apertures, nearly oval, of 12 inches in height, and 10 in width. The piers of the walls between these openings were 7 inches thick. It was through these openings, that the waters passed out of the reservoir by as many leaden pipes, which descended into the valley in part along the sides, and in part over arches rampant, that is, arches whose successive tops formed an inclined plane, which declivity was so regulated as not to have too sudden a descent. Hence they passed to, and over the bridge, and rose again on the opposite side in the same PRELIMINARY ESSAY. 35 manner, and were inserted in the wall of another receiving reservoir. This receiving reservoir differed from the emitting one only in this, that it held the waters flowing towards the bottom of its basin, and the emitting one poured them out from the upper part, about three feet from the bottom, so that while the water rose in the emitting reservoir to three or four feet, that in the receiving one would not rise more than two feet. The nine leaden pipes through which the water flowed, had each eight inches diameter in the clear ; the thickness of the lead of which they were composed was about one inch. Delorme also mentions a circumstance in this syphon aqueduct, which has given rise to much discussion among those who have examined the subject ; he states that these syphon pipes, after having descended about 75 feet, each divided itself into two branches, and that thus the waters are carried the rest of the course over the bridge in eighteen pipes, and until they rise again, on the opposite side, to a height of about 70 feet, at which point they are again united, arid the waters pass on, and enter the receiving reservoir in nine pipes. In opposition to this opinion of Delorme, another eminent architect, who examined the aqueduct, thought that the receiving and emitting reservoirs had the same number of pipes, and that the nine pipes which proceeded from the one to the other, preserved the same dimension throughout. Delorme says that the water in the emitting reservoir, was higher by one foot than that in the receiving one ; but Mr. Villar, a man of science, resident at Lyons, took the level, and found, as might have been expected, that the water in the receiving reservoir was higher by at least 12 inches than that in the emitting reservoir. To construct these individual aqueducts, says another architect, the Roman architects began by forming a trench five feet wide, and ten feet deep, having a uniform slope of one