HEATED BY FERMENTATION. 



435 



wall of this pit, the external course of 

 bricks is constructed of paving bricks 

 (about half the thickness of common 

 bricks) set on edge in cement : the 

 rationale of this arrangement being to 

 admit moist or humid heat at the back, 

 and dry heat at the front. 



Thompson's pit, as figured and described 

 in " Encyclopaedia of Gardening," p. 573, 

 is different from that of M'Phail, by its sub- 

 stituting " stone lintels instead of pigeon- 

 holes to the outside walls. The suspended 

 insulated position of the pits admits a 

 circulation of warm air, both under and 

 all around the pit of each light, whereby 

 a greater degree of surface temperature is 

 obtained, in the absence of solar rays, in 

 the early forcing season. But air-flues run 

 round and under the bottom of the pit, 

 which are covered with a single tile. 

 When the bottom of the pit is laid, the 

 brick on edge is continued up to a con- 

 venient height for the surface hot-air flues, 

 which are also covered with a single tile, 

 laid the reverse way to those at the bot- 

 tom of the pit. Fig. 601 is the transverse 

 section, showing the pits and the position 



Fig. 601. 



of the lintels, which admit the fermenting 

 body of manure to act under the north 

 and south flues. The internal part of the 

 pits is covered with a thin coat of hair 

 mortar, made rough by finishing with a 

 wooden float and brush ; and the tiles are 

 the flat draining tiles, without knobs." 

 These pits are, in general, from 5 feet to 

 6 feet 10 inches in breadth, and may be 

 considered amongst the best of their kind. 



Kendall's double pit. — One object Mr 

 Kendall has had in view in the construc- 

 tion of this pit is the economy of ferment- 

 ing material ; for, the pits being parallel 

 to each other, and having the space for 

 the linings placed between the back of 

 the one and the front of the other, and 

 that carefully covered over, no waste can 

 take place. Another novel feature in this 

 pit is carrying up the walls tapering and 



hollow, which gives great additional 

 strength to them. The walls are a foot 

 thick at the base, and the outside of the 

 external ones is built perpendicular with 

 common-sized bricks, while the inner 

 sides are built of paving bricks, about half 

 the thickness of the others. That the 

 front pit may not shadow the other, it is 

 sunk about 1 2 inches below it. The floor 

 upon which the mould is placed is sup- 

 ported by iron bearers, reaching across 

 the pit, and let into the side walls, and is 

 formed of old boards, branches of fir, pea 

 stakes, or turfs, as may be most conve- 

 nient. This is the only objection we have 

 to this otherwise excellent pit. Why not 

 lay thin pavement, Welsh slates, or plates 

 of cast-iron perforated 1 which would, in 

 either case, last as long as the walls ; 

 whereas the others will be constantly 

 going to decay, besides, from their non- 

 conducting properties, preventing the 

 heat from below from ascending. The 

 vault under this covering or floor is filfed 

 with fermenting matter, introduced at 

 doors at each end, and so gives out a 

 humid temperature to the mould above 

 it, while a dry heat is admitted into the 

 atmosphere of the pit by passing up 

 through the hollow walls. To prevent 

 the loss of heat by absorption through the 

 outside of the linings, precautions are 

 taken to fill up behind them with broken 

 brickbats or other porous material. " Im- 

 mediately above the intended depth of the 

 soil of the pit, a course of bricks on edge 

 is left out, both in the back and front walls, 

 and the walls are then covered from one 

 end to the other by a course of slates or 

 tiles 9 inches wide. Above this the walls 

 are continued hollow to the top, where 

 they are finished with a stone or wooden 

 coping." 



Watson's cucumber pit, figs. 602, 603, 

 604, is thus described by Mr Watson in 



" The Gardeners' Chronicle :" — "The plans 

 show the pit I have now in use, the frame 



