In addition to this, there was another reason, which was quite sufficient in itself to account for the extra substantiality of the dam.  This reservoir is for supplying water to the cloth factories of Verviers, on the Belgian-German frontier.  It is curved in plan to a radius of 1,640 ft., with a length of 771 ft., and the additional strength of the structure due to so flat a curve is probably slight.

It is built of rubble masonry, with ashlar facework, laid in hydraulic mortar.  The total amount of masonry is 325,000 cubic yards.  There are two weirs, at a level of 6 ft. below the crest, each 82 ft. wide.  The total height, including the foundations, which are carried down from 3 ft. to 5 ft. into the rock, is 154 ft., and the breadth of the crest, which carries a road, is 49 ft. 3 in., and at the base 216 ft.  The outlet pipes are carried through tunnels, which are driven on the curve into the hill side a considerable distance clear of each end of the dam.

Another very important structure is the Villar dam, Fig. 15, in connection with the water supply of Madrid, and situated on the river Lozoya.  The storage capacity of this reservoir is very considerable, viz., 4,400,000,000, or nearly thirteen times as great as that of Furens.  The height of the dam is 162 ft., with a breadth of 14 ft. 9 in. at the crest.  It is built on the curve to a radius of 440 ft., and the length of the dam measured along the crest is 546 ft., of which 197 ft. is by-wash, thus describing nearly one-fifth of a circle, and consequently well designed to resist pressure.  The dam is built of rubble masonry in hydraulic mortar, and cost L80,556.

The Stony Creek lower reservoir dam of the Geelong water supply, Fig. 16, colony of Victoria, is interesting as being constructed of concrete, in the proportion of 1 to 81/2.  Its erection occupied eighteen months, and cost about L18,000.  It is curved in plan to a radius of 300 ft., and the greatest depth or head of water is 52 ft. 4 in.  The width at the crest is only 2 ft. 8 in., although surmounted by a heavy coping of bluestone 3 ft. 3 in. broad and 1 ft. 9 in. deep.  There being no facility for making a by-wash at the side, the center of the dam is dished to form a weir 30 ft. long.  There are both outlet and scour pipes, and valves of 2 ft. diameter, and the capacity of the reservoir is 143,145,834 gallons.

The Paramatta dam, in New South Wales, built of masonry in hydraulic mortar, is another instance of a dam built on the curve, and which has resisted a flood of water 4 ft. in depth over the crest; and in the case of a dam of about 40 ft. high across the river Wyre, in connection with the Lancaster Water Works, made of cement concrete in proportion of 4 to 1, there has, according to Mr. Mansergh, frequently been a depth of 5 ft. of flow over it.  This dam is built to a radius of 80 ft. only, and as it measures 100 ft. along the crest, must include about the fifth of a circle.