Description of an improved Forcing Pit, $c. 221 



face line ; the walls 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, and are fastened by a wooden 

 pin and staple at top. In front of the doors is a small area, 

 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, 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, over which is laid 

 the soil for the plants, as represented in the sections. J ust be- 

 low the level of the bars, all round the chamber, are holes 

 passing in a sloping direction through part of the wall into a 

 cavity in the upper part of the wall at the back, front, and 

 both ends of the pit. In order to form this cavity or flue, 

 the wall above the chamber is carried up, externally, with 

 single bricks laid flat, and internally, with single bricks laid 

 on edge, the cavity is consequently two inches wide ; for the 

 purpose of strengthening it, the sides are occasionally tied 

 together by bricks passing through from side to side. The 

 top of the cavity, and of the interior part of the wall which 

 rises at the back and front to the level at which the earth is 

 meant to stand, is covered with tiles, over the joints of which 

 are laid slips of slate bedded in mortar, this effectually pre- 

 vents the steam of the dung escaping : the edges of the tiles 

 which cover the cavity are let well into the external wall, 

 to make the work tight and firm. In the exterior part 



