2175. The reservoirs of water in hothouses are commonly cisterns of stone or timber, lined with lead, or cast-iron troughs or basins. Sometimes, also, tanks are built in the ground, and lined with lead or cement. The cistern is sometimes placed in an angle, or other spare part of the house, and the water lifted from it at once with the watering-pots; but a more complete plan is, to build it in an elevated part of the back wall, where it may have the benefit of the heat of the house, and whence pipes may branch off to different parts of the house with cocks, every 30 or 40 feet, for drawing supplies. Tanks and cisterns below the level of the front gutter may be supplied a great part of the year from the water which falls on the roof; but more elevated cisterns must either be supplied by pumps, or elevated springs. The sources of supply, and the quality of the water, must be taken into consideration before the situations of the cisterns are determined on. In all cases, there must be waste-boxes at the cocks, and waste-pipes from the cistern, to counteract the bad effects of leakage.