21
Most of the plants are fruited in these pits, but some are fruited in a house, ([fig. 21.]) which “though furnished with flues, yet these have been very little used. The heat imparted to the plants is produced by the fermentation of stable-dung in a pit below the plants, the top of which is covered by tiles supported by iron rafters, with the joints closely cemented, to prevent the passage of steam into the house. The pots are neither bedded in tan, nor in mould, but stand on the tiles, and the interstices between them warm the air of the house.”
22
The dung is managed as in West’s pit ([fig. 22.]), but with the addition of being watered after it is thrown in, which is found to promote fermentation, and the intensity of the heat.
One of the earliest instances of steam being used as a bottom-heat with which we are acquainted, was that by Mr. Butler, gardener to the Earl of Derby, at Knowlesly, near Liverpool, in or about 1792. It had been used twenty years before, but chiefly for other purposes. Speechly, in 1796, knew only two instances in which steam was applied as bottom-heat; and, with M’Phail, does not think it will finally answer as a substitute for tan. Instances in which it is adopted, are now much more numerous; but time sufficient has not elapsed, and the opinions of gardeners are yet too unsettled on its merits to enable us to recommend it for adoption in general practice. For heating the atmosphere of hot-houses, there seems little (or at least much less) doubt of its being preferable to fire-heat.
Count Zubow, at St. Petersburg, employed steam to heat a pit or cistern of water, over which, at about three inches distance, a frame, covered with faggots, was placed, and on this was laid the earth, in which his Pines and other exotics were planted without being in pots. The plan is said to have succeeded, and a wholesome temperature to have been obtained and communicated to the mould above the faggots.
Mr. Gunter, as before observed, ([Chap. IV. sect. 13.]) had already tried the use of steam as a bottom heat without success.