434 



PITS AND FRAMES 



tion, to prevent dirt falling into the flue, 

 and also to give the heated air a slightly 

 horizontal direction, instead of an upward 

 one. Under the centre of each sash are 

 openings in the back flue about a foot 

 long, and over it is a cavity formed by 

 the erection of slates set parallel to the 

 wall, and 2 or 3 inches from it, as seen at 

 b in section, for the purpose of admitting 

 heat to the atmosphere of the pit, and 

 within 6 inches of the glass. This pit is 

 furnished with air-drains running across 

 under the floor level, and these 9-inch 

 drains communicate with the bottoms of 

 the back and front flues, with a view to 

 create a draught or current of air, to sup- 

 ply the place of the warm air that escapes 

 into the pit. The side walls of the lin- 

 ings are very properly battered, which 

 gives them greater strength to resist the 

 pressure of the surrounding soil. This is 

 one of the best pits we know for the pur- 

 pose intended ; still, we think it would 

 be improved by having an aperture 

 through the end retaining- walls, brought 

 up behind them to the surface by an 

 earthenware tube, and covered with a 

 grating ; or, where such an arrangement 

 would not be in the way, a small area, 

 say 9 inches square, or more, and covered 

 in the same way, to admit a greater sup- 

 ply of air for the better working of the 

 air-drains and flues already described. 

 Either of these openings, however, should 

 be made so that they could be opened or 

 shut at pleasure. 



Atkinsons early forcing-pit, fig. 600, is 

 sunk under the ground-level, as shown in 



Fig. 600. 



cross section. The main part of the pit a 

 is filled with tan, leaves, or stable litter, 

 and the heat maintained by means of 

 linings in the spaces c c ; the back wall is 

 built open, or in the dovecot fashion, to 

 admit the heat from the linings to enter 

 the pit ; but, as a provision to prevent 

 rank steam from entering also, Welsh 



slates are set on edge in front of this wall, 

 and about 3 inches from it. The vacuity 

 thus formed is closed at top by a movable 

 covering of slate, so that the vapour can 

 be admitted or excluded at pleasure. The 

 front wall is built with piers, the openings 

 between which are filled with large slates 

 set on edge, and fixed in the centre of the 

 wall. This is with a view to admit heat 

 from the front linings unaccompanied by 

 steam, which heat finds its way into the 

 atmosphere of the pit through the vacuity 

 formed between the front wall and an 

 interior 4-inch one, which separates the 

 vacuity from the bed. Any matter that 

 may fall into this cavity during the pro- 

 cess of filling is easily extracted by intro- 

 ducing a narrow hoe at the ends, where a 

 provision is made for that purpose by 

 taking out a movable stone or tile. 



Atkinson's late forcing-pit is in many 

 respects similar to the last, only it has 

 open brickwork all round, with a vacuity 

 formed by setting up slates parallel to 

 the walls, and covered at the top like the 

 last. The intention of this pit is to keep 

 up a sufficient degree of heat in autumn 

 with a very limited extent of steam, as a 

 drier heat at that season is more desirable 

 than it would be in spring and during 

 summer. Both pits are formed with gut- 

 ters in front for taking off the rain water, 

 and the walls are supported by piers. 

 The retaining walls between the linings 

 and the soil are coped with stone coping 

 3 inches thick, and the whole is neatly 

 covered in with boarded coverings. 



Atkinson's melon pit in principle does 

 not differ from the early and late forcing 

 pit of the same artist, but it has certain 

 differences of detail. The retaining walls 

 are battered a good deal, which not only 

 enables them to resist the pressure of 

 the soil behind them, but also increases 

 the capacity of the space for the linings 

 at the part where their heat is of most 

 use — namely, at the top. Another feature 

 in this pit is, that the front walls are built 

 14 inches thick, and hollow, which cavity 

 is open at the top inside, whereas the back 

 and end walls are only 4 inches thick, 

 and constructed in the pigeon-hole man- 

 ner. The wooden coverings for the linings 

 are kept well up, to allow of a sufficient 

 amount of air, which promotes fermenta- 

 tion, as well as the preservation of the 

 boards themselves. In forming the front 



