HEATED BY FERMENTATION. 



431 



beds so situated are much easier got at 

 for the purposes of internal arrangement. 



The Alder stone pit is a walled pit above 

 ground, according to the material em- 

 ployed, of 4 or 9 inch work, supported 

 on iron pillars 3 feet in height, which is 

 the depth of the sunken part. These 

 pillars are set in blocks of stone, and are 

 tied together at the top by a plate of 

 iron, on which the walls rest. The brick 

 walls forming the sides and ends of the 

 pit are coped with wood or stone, into 

 which the rafters are fixed. Linings are 

 applied in the usual manner within a 

 walled trench, and are covered with 

 strong boarding. The interior of the pit 

 is filled with dung, leaves, or tan, either 

 separately or mixed together. The mode 

 of supporting the brickwork part of this 

 pit is good, as the iron supports occupy 

 much less space than stone or brick piers 

 would do, and are much stronger. This 

 was one of the earliest improvements in 

 pit-building ; still it is singular to find so 

 few examples of this excellent pit in pre- 

 sent use. These pits are built parallel to 

 each other, as may readily be done : a 

 great saving of heating material will be 

 effected, as well as of labour in attending 

 them, as the back lining of the one heats 

 the front of the other. These linings are 

 3 feet deep, and the back wall above the 

 covering of the lining is 2 feet 3 inches, 

 while the height of the front wall is 1 foot 

 6 inches. 



M'PkaiFs pit, fig. 595, may be de- 

 scribed as consisting of two parts — the 



frame and 

 Fig. 595. lights, which 



are both of 

 wood, al- 

 though often 

 and better 

 the frame is 

 dispensed 

 with, and 

 bricks on 

 bed are sub- 

 stituted : the 



„___ second part 



is the base- 

 ment, on which the frame is placed, con- 

 sisting of flues of brickwork, having the 

 side or outer walls built open, as shown 

 in section. Round these pigeon-hole walls 

 linings of fermenting material are placed, 

 the heat of which enters the flues and 



heats the mould in which the plants grow. 

 This pit is objected to upon the same prin- 

 ciple as the last — namely, a great waste 

 of heating material, and often an insuffi- 

 ciency of heat. 



MearvCs pit, fig. 596, is one of the best 

 pits heated by fermenting matter, a a are 



the side walls in open brickwork • b b b the 

 hot-air chamber or cavity into which the 

 heat and steam of the linings are admit- 

 ted ; c c posts of iron or stone supporting 

 a bed or trough d, made of slate, stone, or 

 tiles — the former to be preferred — and 

 extending the whole length of the pit; c c 

 slabs of slate employed to close the space 

 between the trough and side walls, which 

 should be closely jointed to prevent the 

 entrance of too much steam into the pit. 

 At an early part of the season the heat is 

 freely admitted into the pit, the slate 

 slabs being at that time only thinly 

 covered with mould : / / are dung linings ; 

 g g retaining walls, to form the space for 

 the linings ; h h drains to keep the dung 

 dry at bottom ; i shows the hill on which 

 the plants are first set ; and k marks the 

 height of the mould when filled up for 

 the season. This otherwise excellent pit 

 would be greatly improved if the space 

 over the linings was covered with portable 

 boarding, as indicated by the dotted lines. 

 Indeed, the linings of all such pits should 

 be covered over, as sufficient air will 

 always find its way in to promote fer- 

 mentation, without which it would cease 

 altogether. No pit has a finished appear- 

 ance if the linings are left exposed; and 

 they suffer much in temperature as well as 

 waste of material, in consequence of being 

 often saturated with wet or melting snow. 

 A considerable amount of heat must escape 

 from them in an upright direction, which 

 would be prevented by their being en- 

 closed in the manner we have suggested. 



