1993. The adjusting-bottomed frame, has a box for the earth, of the size of the inside dimensions of the frame; and the frame, being deep or placed on walls, like those of a pit, the bottom and its earth and plants, or its pots and plants, may be raised or lowered by a machine composed of a pinion and screw, or any other equally convenient power. The bottom is composed of perforated boards, and it has boarded sides to keep in the earth. The object is to prevent plants from being burnt when the dung is very hot, by raising them; also, to be able to raise them close to the glass when young, and to lower them in cold nights. The chief difficulty in managing this frame is, to keep the earth it contains of uniform moisture. Lawrence, in the last edition of his Kalendar (1715), suggests the idea of putting a bottom of wire to the frames of hotbeds, and of covering it with flat tiles, placing over these the earth, &c., so as to admit of the whole being lifted, and the dung below stirred or renewed at pleasure. He says he has not seen it done, but merely suggests it as a hint to the ingenious. A century afterwards, J. Weeks, of the Horticultural Manufactory, King's Road, London, invented his patent forcing-frame, which is that just described.
