80 PRACTICAL GARDENING. 



is a conuiion conical boiler, of a proper size, with pipes in 

 proportion to the work tliey have to do ; and as they require 

 very little attention, it is better to let there be several of 

 these than it is to have too many tilings heated by the same 

 boiler, be the construction what it may. The less compli- 

 cated everything is, and the less expensive it is, in the con- 

 struction as well as in use, the better. A range of pits — say 

 four feet high in front, twelve feet from back to front, ten 

 feet high at the back, with a good shelf within two feet of the 

 roof, alan-pit along the centre, three feet from the front and 

 the like from the back, three feet six inches high in front, 

 and five feet at back — ^will be found as useful, for nearly 

 every kind of forcing in pots, as any other that can be adopted. 

 The whole of these should be built ^\dth the bottoms off the 

 ground, which can be accomplished by single courses of bricks 

 on edge, every three feet, from back to front, and stones or 

 slates laid on of proper width, a grating of iron being along 

 the front next the wall, one foot wide, and the back path to 

 have a grating about twice the width. These gratings form a 

 direct communication with the hollow below the false bottom 

 of the house. A good shelf may be placed along the front of 

 the house, one foot, or even eighteen inches wide, and some- 

 thmg between them; because these forcing-houses, or pits, 

 are not made to walk about in ; and the fewer people go in 

 and out, except those engaged, the better; so that con- 

 venience, by means of wide paths and abundance of walking- 

 room, is not to be studied for an instant. The iron piping 

 required for this building, in addition to the ordinary heat of 

 the tan, will be two four-inch pipes the whole length of the 

 front, the one close to the wall, the other a little below, but 

 occupjung a second width, for the purpose of covering, as it 

 were, as nearly as may be, the width of the grating ; and the 

 heating will be still more complete, if there be a row of 

 paving-tiles along the path, to confine the air that comes 

 through the grating, and force it to pass close to the pipes. 

 One of these pipes ought to be nearly close to the ground, 

 and the other six inches from it. All the air that comes 

 through the grating will be heated as it passes the pipes ; 

 and when it has traversed the upper part of the house, and 

 cooled a httle, it will natui-ally descend through the grating 

 behind, and be drawn to the front, to be heated again. The 

 shelf in front should be formed of bars, that it may not inter- 



