400 Sloan's Architectural Rcvieio and Builders' Journal. [Dec, lights in floors. At least this thick glass might be used, to advantage, as a covering for cisterns, in a hinged frame, to be left open, as often as safety would permit. Silicate of Potassa would make an excellent coating for a brick cistern, and present all the advantages of glass, with- out the necessary joints. But the majority of these materials proposed for the formation of cisterns, are expensive; and, as our aim, end, and object is, to benefit the community at large, we would recommend the forma- tion of cement cisterns, of the simplest forms ; as, for instance : Dig a circular hole, in the chosen site, and rough-wall it with stone, or brick, finishing by coating the surface and bot- tom with pure cement, on a thick coat of cement and sand, in equal propor- tions. This will make a good ordinary cistern whence to draw water. When an elevated piece of gi'ound can be had, within any reasonable dis- tance from a building, which it is re- quired to supply with water, possessing an altitude equal to that of the eaves of the roof, we would recommend that the cistern should be placed on such rising ground j so that the surface of the water when the cistern is full, should be ex- actly on a level with the eaves, or a little below, if possible ; and, as the supply becomes exhausted, the surface of the water will be lower and lower beneath that level, onty varying the depth of the cistern. It is needless to say, that it should never be so located, that the level of the water in the cistern would be higher than the eaves, whence the supply is derived, as any one ac- quainted with hydraulics, knows that this would be going against all the acknowledged rules of that science. The rain-water from the roof will be collected from the different gutters, and concen- trated into one main iron pipe, extend- ing up to the eaves, having the joints calked, to enable it to withstand the pressure of the head, thus obtained. This pipe will be brought down from the eaves and run into the ground a depth sufficient to protect it from frost ; and then continued underground until fairly connected with the bottom of the reser- voir. By having the top of the latter, on a level with the eaves of the building, this supply-pipe will also answer for the purpose of distributing ; and connections can be made for that purpose, wherever it is desirable. This iron supply-pipe, from the eaves downwards, should, in all instances, wherever the climate is cold enough to freeze, be placed in a flue, made to receive it, so arranged as to admit of a circulation of warm air, during cold weather. When cisterns of large dimensions are required, the best mode of construct- ing them, is to dig a horizontal trench, from six to eight or ten feet in width, and of any required length ; and, within this, form a circular tube or horizontal cistern, of almost any diameter, or length, that may be wished. When they are of large diameter, the shell should be built of hard-burned brick, straight and of uniform size, in order to make close joints; and' should be from one foot to one foot four inches thick, laid in concentric separate rims or courses, one above the other, in cement, mixed with one-half sand, except the inner rim, which must be laid in pure English Portland cement, with a coating of the same on the inner surface. The exterior should be well packed with earth ; and, in all cases, the top surface should be at least three feet six inches below the surface of the ground. When cisterns are constructed in this "manner, they can be extended, so as to contain larger quantities of water, retaining, at all times, an uniform depth, not varying more than its diameter. Such are also easy of access, for the purpose of being- cleansed. Whenever this is desirable, in choosing a site for such cisterns, regard should alwaj-s be paid to drain- age. A waste-pipe should be connected with the lowest point of the supply -pipe,
