The dredges employed at the barrage, of 20 horse power, and raising sand from a depth of seven metres, filled thirty-three lighters in the day and twenty-eight in the night, in all 61 _per diem_, giving a total of 610 to 700 _met. cub._; but these machines were almost continually stopped for want of a sufficient number of lighters. These same dredges, on the Seine, removed as much as 500 _met. cub._ in the day, and an equal quantity at night, excavating, it is true, at a depth of only 2 _met._ 50. The price paid per cubic metre was 0 _fr._ 75, including carrying away and discharging. At the barrage, on account of the low price of labour, the cubic metre has not cost 0 _fr._ 50. For deepening the roadstead of Toulon, dredges of twenty-five horse power were employed, which raised the mud from a depth of 9 _met._ 50 below low water. These dredges worked 270 days in the year, and each raised 194,755 _met. cub._ The cubic metre of soil extracted was fixed provisionally for the account at 1 _fr._ 20, including the transport and discharge, which was at an average distance of several miles in the open sea. At the port of Valencia, dredges of thirty-five horse power were employed, raising 750 _met. cub._ _per diem_, from a depth of 5 to 7 _metres_. A steamer of seventy horse power towed the lighters to a distance of fifteen miles, and the cubic _metre_ thus raised and transported only cost 0 _fr._ 75. From these data it may be assumed, that the dredges of twenty horse power will raise 500 _met. cub._ of earth _per diem_ from a depth of 4 _met._, and we may fix the price of extraction, including transport, at 0 _fr._, 75; that the dredges of thirty-five horse power will raise 750 _met. cub._ at 1 _fr._ By causing the dredges to work day and night, and assuming, as we have said, an average of 250 working days in the year, a dredge of twenty horse power will excavate _per ann._ 250,000 and a dredge of thirty-five horse power 375,000 ------- _met. cub._ 625,000 The total quantity of excavation to be performed by dredges being 57,205,342 _met. cub._, if the work is to be done in five years, it will be necessary to have nineteen pairs of dredges; and, if it be observed that for the greater part of the Isthmus, the excavation may be done by hand to the depth of a foot at least below the level of the Mediterranean, since the bottom of the Bitter Lakes remains dry at a depth which reaches 8 _met._, 58, it will be found that nineteen pairs will be amply sufficient. Supposing half the work to be done by each kind of dredge respectively, the cost is found to be 50,054,674