. Cassell's popular gardening. Gardening. 276 CASSELL'S POPULAR GARDENING. valves should always be used where boilers are coupled together, in all mains, and wherever it may be thought desirable to effectually shut back the water in case of break-down or acci- dent. The thi-ee valves (Figs. 52, 53, 54) manu- factured by Foster and Pearson, of Beeston, to which the Horticultural Society's medal has been awarded, are admirably suited to this purpose, as they answer the two-fold purpose of valve and stop-tap. Valves are sometimes placed in front of H-pieces (Fig. 55) when a flow an
. Cassell's popular gardening. Gardening. 276 CASSELL'S POPULAR GARDENING. valves should always be used where boilers are coupled together, in all mains, and wherever it may be thought desirable to effectually shut back the water in case of break-down or acci- dent. The thi-ee valves (Figs. 52, 53, 54) manu- factured by Foster and Pearson, of Beeston, to which the Horticultural Society's medal has been awarded, are admirably suited to this purpose, as they answer the two-fold purpose of valve and stop-tap. Valves are sometimes placed in front of H-pieces (Fig. 55) when a flow and return pipe run through. Pi^ 55.—H-piece with Valves. several compartments, say a, b, c (Fig. 56); by placing the castings, say at o, a can be heated by A B C O P Fig, 56.—Heating Compartments separately. shutting the valves, a I, while b and c remain cold. By opening them at o, and closing them at p, a and B can be heated, while c remains cold; and by open- ing aU the valves, the three sections will be heated. H-pieces are often made with valves at with an air pipe at the extreme limit of c, these are of no practical value. Boilers.—The number of these before the public is now very great, and, at first sight, almost for- midable ; but when classified and divided into three or four sections, to which nearly all of them belong, the difficulty in choosing a boiler for any special purpose is not so great as many imagine. The power of a boiler depends upon the area of heating surface, and the amount of heat given out depends upon the position of that surface, and the way in which a boiler is stoked. If every square foot of eiiective heating surface in a boiler is equal to the heating of forty to fifty feet of four-inch piping, and fifty to sixty feet of three-inch, it is easy to decide upon the boiler capable of doing the work, provided always that we take oil thirty per cent, of the manufacturer's calculation, and take two boilers to heat, say, one thousand feet, whe
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Keywords: ., bookcentury1800, bookdecade18, booksubjectgardening, bookyear1884
