The reservoir on the summit of the hill contains the water required for the use of the building, and for the fountains throughout the grounds. Close to this reservoir is an engine-house, containing the steam-engines that raise part of the water into two large tanks erected on columns at the north end of the building close to the junction of the Sydenham and Dulwich roads. The columns, twenty-four in number, are of hollowed cast-iron, one foot in diameter. The central column, which is two feet in diameter, supporting a portion of the superincumbent weight, and making up the number, twenty-five, is the water-pipe, by which the tank is fed, and which forms also the conduit to the fountains in the building, and on the terraces. These two distinct actions of filling the tank and working the fountains proceed simultaneously through the same pipe. On the top of these columns are massive girders which support the plates, forming the bottom of the tank. The height from the stone curb of the reservoir to the bottom of the tank is 65 feet; the tanks are each 47 feet square by 15 feet deep, and capable of containing 207,000 gallons or about 900 tons of water. They supply also the water required in the building for the plants and kitchens, and charge the pipes provided against casualties from fire. The vast residue of the water in the great upper reservoir, in consequence of the sloping character of the ground, does not need any help from the engines, but flows direct to fountains on a lower level, and plays smaller jets. Through the same convenience, the waste water from the upper fountains is used a second time in the lower fountains. The central or intermediate reservoir collects the waste water from the displays which take place on ordinary days, and which include all the fountains, save the two largest, and the cascades. Attached to this reservoir are also engines which pump the water back to the upper reservoir. The lowest reservoir collects similarly the waste water from the displays which take place in the two largest fountains on the days of great exhibition, and its engines return the water at once to the top level. THE FOUNTAINS.