164 



FIXED STRUCTURES FOR GROWING 



which a bed of leaves within is heated by a dung-lining placed on the 

 outside of a pigeon-holed wall, and extra heat is provided for by three 

 turns of a flue, one above the other, in the back path : a is the pit in 

 which the dung-lining is placed and covered with a hinged shutter ; 



Fig. 135. 



Fig. 136. 



Pinery heated by dung-linings. 



b, the surface of the bed of leaves, in which pine-apples, or cucumbers, 

 or melons may be grown, or strawberry -plants or flowers forced ; 



c, door; d, flues; e, front pigeon-holed wall; and/, end pigeon-holed 



wall. Fig. 136 shows a mode 

 of applying dung under a 

 bed of soil without coming 

 in immediate contact with it, 

 and by which no heat what- 

 ever produced by the dung 

 is lost : a is the bed of soil in 

 which the vines are planted, 

 and which is supported by 

 cast-iron joints and Welsh 

 slates ; and b shows the open- 

 ings furnished with shutters 

 by which the dung is intro- 

 duced. Beds on the same 

 plan, but wider, have been 

 used for growing pine-apples 

 and melons, and for various 

 similar purposes. An extra 

 supply of heat from the dung 

 may be obtained bv having 

 panels of slate in the inside 

 wall, c, to be kept covered 

 by wooden shutters, except when extra heat is wanted ; or by 

 tubes, as in fig. 134 ; or it may be rendered unnecessary by extra 

 coverings. The first forcing which we read of in the history of British 

 gardening was effected, as Switzer informs us, by placing casings of 

 hot dung against the north side of walls of boards, against the south 

 side of which cherries were trained. 



Heating from Vaults, or from Stacks of Flues. The oldest and sim- 

 plest mode of applying fire-heat to hothouses was by means of a pit 

 in the floor, or a vault under it. In the ' Gardener's Chronicle ' of 

 Oct. 2, 1869, a full account of hypocaust heating is given. The 



Section of a vinery heated by dung. 



