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 curvature. 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 distribution 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.