BOOK III. 



MOVEABLE STRUCTURES. 



301 



cases fermenting litter thrown 329 



in. A great improvement on 

 this species of pit has been 

 made by J. West, of Castle Ash- 

 by, Northamptonshire. The 

 principle of the improvement 

 is the facilitating the passage 

 of the heat from the vault to 

 the bed of earth over it by sub- 

 stituting a thin floor of boards 

 or slates, or wattled hurdle, for 

 brick-work ; the walls are also flued, and the heat supplied is that of fermenting dung, 

 litter, weeds, &c. On the whole it seems an excellent improvement. Nine years' expe- 

 rience enable its inventor to recommend it for neatness of appearance, the power of 

 regulating the heat to the greatest nicety, and for forcing asparagus, strawberries, and 

 the most delicate kind of cucumbers. By raising the walls of the pit higher above the 

 earth, it is evident it would answer equally well for growing pines, or forcing shrubs, or 

 any other purpose to which pits are applied. 



1547. In West's pit the dttng is placed in a chamber (e) three feet and a half deep, 

 being about eighteen inches below the surface-line ; the walls (g) which surround it are 

 nine-inch brick-work ; both on the front and at the back of the chamber are two openings 

 (), about two feet six inches square each, with moveable doors through which the dung 

 is introduced ; the doors fit at bottom into grooves (6), and are fastened by a wooden 

 pin and staple at top. - In front of the doors, is a small area (o) sunk in the ground, 

 surrounded by a curb of wood, by which the introduction or removal of the dung 

 is facilitated. Along the centre of the chamber is a bar (d), which serves as a guide 

 for packing the dung ; and across the top, at intervals of twelve inches, are placed, 

 on their edges, cast-iron bars (/*), two inches wide, and three quarters of an inch thick, 

 to support a layer of small wood, bushes, and leaves (i), over which is laid the soil for 

 the plants (/t). Just below the level of the bars all round the dung-chamber, are 

 holes (/), passing in a sloping direction through part of the wall into a cavity (g) in 

 the upper part of the wall at the back front and both ends of the pit. In the exterior 

 part of the back wall are holes with plugs (/), to let out the steam and heat at discretion. 



230 



At the commencement of forcing, half the chamber is filled longitudinally with dung, 

 and if the doors are kept shut, this will afford 

 sufficient heat from twelve to eighteen days. As 231 



the heat declines the other half of the cham- 

 ber is filled, and the temperature is kept up by 

 additions to the top of the dung, on either or 

 both sides, as it settles. When the united heat 

 of the two sides ceases to be sufficient, the side 

 first filled must be cleared out, and mixed with 

 fresh dung and replaced, and so on, adding and 

 turning as circumstances require. (Hort. Trans. 

 iv. 220.) 



1548. As an improvement on the construction 



