563. The garden engine has been repeatedly mentioned, and its use recommended, (5 92, 205, kc.) Considerable improvements having been made on this instrument at Edinburgh, a few words additional concerning it may be excused. The engine consists of a force pump or barrel, commonly two inches and a quarter in diameter, to the bottom of which, above the valve, is connected an air vessel : into this the water is forced ; and it is emitted from it, by the action of the compressed air, through the direct ing pipe in a continued stream. This pipe is attached to the top of the air-vessel by means of a swan-neck swivel joint, with double screws, which are water tight : in this way the pipe can be moved in any direction. Formerly, leathern valves and a leathern flexible director-pipe were in use ; but from occasional exposure to drought, the seams of the leather were very apt to open, and allow water to escape ; well executed brass work, on the other hand, is of all others least liable to derangement. The pump and air-vessel are fixed in a copper cistern, sixteen inches deep, and capable of containing about twenty-two gallons of water, wine measure. The cistern has likewise a strong
wooden bottom, to which tiro attached two provement of Mr John Hay's, which greatly facilitate the moving of it when taken into hot-houses or vineries. The engine is, at the same time, fitted to a hallow with wheels, for the convenieney of wheeling it through the garden ; and to this the rollers form no obstacle, as they pass between the steels or the barrow. The pump is worked by a lever, and requires very little exertion. The water can be pro jected about fifty feet ; so that wall trees of any height may be trat..hccl, whiie the engine remains on the gravel walk.
The best writers on the various branches of horticul ture, particularly British authors, have been mentioned, either in the introduction to this article, or in the course of treating the different parts of the subject ; but it may be useful to recapitulate them here in alphabetical order. (r. N.)