HEATED BY FERMENTATION. 



433 



be of wood, as at present, as being a good 

 non-conductor ; and through the linings 

 and boarding we would introduce metal 

 tubes to carry heated air into the interior 

 of the pit, in the way proposed by Knight. 

 Vide p. 430. Enclose the linings within 

 stone or brick retaining-walls ; cover 

 them with portable boarding ; substitute 

 cast-iron uprights, with malleable-iron 

 rods run through them, as suggested 

 above ; form the framework above the 

 level of the linings with double boarding, 

 packing the space between with charcoal; 

 and we would have in this form of pit 

 one of the most economical, durable, and 

 useful pits that could be desired. 



The Edmonstone pit, fig. 598, is one of 

 the best of its kind. It may be of any 



Fig. 598. 



a 





b 



• 



! 



c $ 



i i 



d \ 



9h A 



1 





length, and is 6 feet in breadth, which is 

 the usual width of all pits heated by lin- 

 ings. The height of the back is 5 feet, 

 and that of the front 3 feet 9 inches. The 

 spaces for the linings are 2 feet 3 inches 

 broad, and 3 feet deep. The outside walls 

 of the linings are of 9-inch work, and 

 finished on top, level with the ground, 

 with a course of hewn stone. The linings 

 are covered with boarding, the boards 

 having rings in them for lifting them by, 

 and being of convenient lengths. These 

 boardings rest on a check cut out of the 

 stone plinth or coping, and on the scarce- 

 ment or projecting part of the side walls. 

 Although shown in our sketch level, which 

 was the original plan, they would be 

 better if laid slightly inclining towards 

 the outer sides, for more readily throwing 

 off the rain water. Such pits may be 

 built upon the pigeon-hole principle, or 

 9-inch brick piers may be carried up at 

 equal distances, and the spaces lintelled 

 over; or, where pavement is abundant, 

 they may be formed of 3-inch flags set on 

 edge, secured at the base by building 

 between them, and lintelled over as above 

 for the reception of the 4-inch brick 



VOL. I. 



walls that form the upper or above- 

 ground part of the structure. 



Knight's melon pit has a peculiarity both 

 novel and useful — namely, at each of the 

 lower corners is a drain or cavity, which 

 extends along the surface of the ground 

 under the linings, and communicates with 

 the cavities in the walls, which are built 

 cellular, into which it admits the external 

 air, to occupy the place of that which has 

 become warm, and passed into the pit. 

 These drains are secured with iron grat- 

 ings, to exclude vermin. These pits are 4 

 feet high at the front, and 5 feet 6 inches 

 at the back, and are capped with wooden 

 wall-plates, as in ordinary cases. The in- 

 terior is filled with leaves or tan, and 

 heated without by dung linings. The 

 linings are exposed to the weather, which 

 occasions great waste of material. It was 

 in such pits that that excellent man and 

 ardent horticulturist grew his melons in 

 pots, training them on a trellis at a pro- 

 per distance from the glass. We should, 

 however, here observe, that during these 

 experiments he employed no heating ma- 

 terial within, but trusted to that afforded 

 by the linings from without. 



The Hechfield melon pit, fig. 599.— -This 

 pit differs from the pigeon-hole pit, and 



Fig. 599. 



also from M'Phail's, which it nearly re- 

 sembles, but is, at the same time, an evi- 

 dent improvement on it. The walls are 

 built hollow, forming a hot-air flue from 

 their bottom to the ground-line. The 

 course of bricks used for covering the 

 back and end flues projects 1 inch beyond 

 the face of the wall outside all round, 

 forming a support to the boarding which 

 covers the lining. The front flue is cov- 

 ered also with bricks, but laid lengthways 

 and across ; or, as bricklayers would say, 

 a header and stretcher alternately, leaving 

 an opening between each header to admit 

 the heated air of the flue into the pit. 

 Narrow slips of slate are fixed in the joint 

 immediately over the headers at a in sec^ 



3 i 



