5248 COTTAGE, FARM, AND VILLA AUCHITECTURE. apparatus, it must be kept in view, for the sake of economy, that all the mains may be of small half-incli pipe, which does not cost above 3d. or 4(1. a foot, while the heating pipes under the floor of each dwelling, in order to give them abundant power, may be of six or eight inches in diameter. In the management of steam, with a view to economy, it should always be remembered, that it dirters from water in this, that the mains may always be exceedingly small, however large may be the service pipes. Where steam is to be conveyed to a distance, this is a very great advantage. 499. Arrangement of the Dwellings. These, as before stated, are in eight divisions ; by referring to the plan, fig. 440, it will be seen that the limits of each row of ten dwellings is determined by the carriage or foot entrance to the offices, at 10, at one end; and by the public water-closets, at </, at the other. We shall show, in succession, the mode of heating, and of supplying one of these divisions with water, the construction of the water-closets and manure tanks, and the drainage. 500. For heating each line of Dwellings, a steam or hot-water main proceeds direct from the central fire, to the end of the line, at 10. If steam be used, the main is there connected with two cast-iron pipes, the one under the floors of the living-rooms, six inches in diameter ; and the other, under the floors of the bed-rooms, tliree inches in diameter. The main, and these pipes, must be laid with a gradual inclination from the boiler to the further extremity of the water-closets, which it also heats ; and there e.ach pipe must have a small return tube, gradually descending froin that point to the boiler, to admit of the condensed water running back of itself. The mains, between the boiler and the dwellings, will be placed isolated within earthenware pipes ; and these, and the return pipes of condensed water, will be included in a dry di-ain, filled with charcoal or coke. All the difference of level requisite to return the condensed water need not be more than one foot ; so that, if this drain be two feet deep, the pipes will be sufficiently protected from the influence of frost. Under the floors of the dwellings, the drain need not be above ten inches broad and one foot deep, and it may be covered with one-foot tiles; or, the tubes may be made square, and their upper surface may serve as part of the floor, as suggested in fig. 282, for Laxton's small college, § 290 ; and also in § 489, for our college of twelve families. Should Perkins's hot-water apparatus be preferred to steam, common gas pijie may be used throughout, both for the mains and service pipes. A description of this mode of heating will be found in the Repertory for Patent Inventions, for March, 1832, and a more particular account in the Gardener's Magazine, vol. viii. p. 292, by Mr. Perkins himself. Should Mr. Perkins's apparatus be adojited, there
