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HISTORY OF ENGINEERING.

Boost I.

work was performed was as follows : — Alevel pavement was formed of brick, onwhich was raised a frame or caissoon oftimber planks; against the sides of this,squared stones w’ere laid in regular courses,and their interior filled in with rubble, in adry state, after which a grouting of liquidcement was poured in to consolidate thewhole. Lime, fine gravel, or sand, mixedwith a due proportion of water formedthis grouting; after a sufficient time hadbeen allowed for the work to consolidate,the caissoon was mounted upon anothercourse or layer of tiles, and similar oper-ations to the first took place.

The bricks or tiles used are 1 foot9 inches in length, 12 inches in breadth,and an inch and a half in thickness.

The whole of the water conduit wascoated with cement; at the bottom itsthickness was 6 inches, at the sides aninch and a half: 24 inches from the bottomof the canal, at every 30 inches distance,iron ties were inserted to hold the sidewalls together, and prevent their beingpressed outwards.

The three aqueducts of the ancientLugdunum were traced for many milesto the source of the waters they conducted,by M. Delorme, who, in 1759, gave to theseance de l’Academie an account of hisresearches. The Mont de Pile derived itssupply from the river Gierre and somesmaller springs in its vicinity. These

PLAN OP CA8TELLT7M.

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ARCHES IN THE VALLEY,

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PIER OP ARCHES.

Fig. 208.

waters having been conducted over eight bridges, across the valley where the ninth wassituated, the syphon was carried over. The valley at the foot of the heights of Soncieuis very dee]), and where the aqueduct crosses, was a large reservoir, constructed on thesouth side of the river Garon.

Here we have an example showing us that the Romans well knew, when water wasbrought down one side of a hill, how to make it rise on the other: why this plan wasadopted in preference to building a series of arches, like the Pont du Gard , we are notinformed; but the arrangement proves that they practically understood that water wouldfind its level, what precautions to take to expel the air, and the advantages of a venter.

Leaden pipes of large dimensions, bedded on the sides of the valley, conducted the waterto others, laid over a bridge in an inverted curve; they were then continued up the oppositesides of the valley, and delivered the water into another reservoir, of corresponding level tothe one on the hill before described. The aqueduct then took the name of Chaponest, fromthe hill where the last reservoir was situated, and the waters were conducted undergroundalong the west side of the village. A bridge of 90 arcades carried it to another reservoir, whenit again descended into the valley in similar leaden pipes, passing over the river Baunan in aninverted curve, and again mounted to a second reservoir at St. Foi. A series of arcades con-ducted it to level ground, sometimes above, at others below; it continued its current till itreached the gate of St. Irenee, where was another reservoir; leaden pipes conducted itthrough the fosse of St. Irenee, when it mounted once more, and was discharged into anotherreservoir, near the Gate of Trion ; in this instance the pipes were bedded in a mass of solidmasonry, and not carried over a bridge.

The total length of the course of this aqueduct was 13 leagues, in which distance it hada fall of upwards of 350 feet.

The reservoir, which emitted the water at the aqueduct bridge of the Garon, was built atthe top of a tower; its length was 14 feet, and its breadth 4 feet 6 inches. On the side towardsthe valley 9 oval holes were made, at 9 feet from the bottom, about 12 inches in height,and a little less in width ; through these passed the leaden pipes, which descended into thevalley, crossed over the bridge of arches, and rose on the other side in the regular and uni-form curve of a great syphon. When the water reached the reservoir destined to receive iton the opposite side, it entered at the top, and was emitted at the bottom : the leaden pipeswere 8 inches diameter in the clear, formed of metal of an inch in thickness, and thewater in the emitting reservoir was always a foot lower than in that which received it. One