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 foot in 600. In this trench they formed the aqueduct or water channel of masonry,

keeping the same dimensions in the parts excavated from the rock, as in those which were cut into the clay or ground soil.

The bottom of this trench was laid with masonry, a foot thick on this, two walls ;

were erected, each 1 1-2 feet thick, and 5 feet high, and having a space between them of 2 feet, which formed the canal for the passage of the water this space was enclosed on ;

the top by a semi-circular arch 1 foot thick, and then covered with a layer, 2 feet thick, of earth. The bottom of the canal had a coat of cement 6 inches thick, and a coat of 1 1-2 inches on the sides, which reduced the intervals between the walls to 21 inches. The angles were formed by the sides and bottom, rounded by cement. The walls were constructed with small rough stones, from 3 to 6 inches in thickness, laid in a bed of mortar, so that no void was left between the pieces.