70 



BRITISH MODES OF CULTIVATING 



being applied to them in cold frosty weather. The 

 north wall of a pit for this purpose had best be only 

 about four feet above the ground ; and if about two 

 feet high of it the whole length of the wail begin- 

 ning just at the surface of the ground four feet be- 

 low the height of the wall, be built in the form of 

 the outside walls of my cucumber bed, the lining 

 will warm the air in the pit more easily than if the 

 wall were built solid. The linings of dung should 

 not be lower in their foundation than the surface of 

 the tan in the pits in which the plants grow (for it 

 is not the tan that requires to be warmed, but the 

 air among the plants) ; and as during the winter 

 the heat of the air in the pit . among the plants, 

 exclusive of sun heat, is not required to be greater 

 than from sixty to sixty-five degrees, strong linings 

 are not wanted : one against the north side, kept 

 up in cold weather nearly as high as the wall, will 

 be sufficient, unless the weather get very cold in- 

 deed, in which case a lining on the south side may 

 be applied. In cold frosty weather a covering of 

 hay or of straw, or of fern, can be laid on the 

 glass above mats in the night-time. 





