FART V. CULINARY GARDENING, 297 



structed, this covering should not be neglected, as is too fre- 

 quently the case; it being of very great importance in preserv- 

 ing the heat, and preventing chilly dews, frosts, Sec. 



3. Pits are constructed upon the same principles as hot- 

 houses. They are of great use in raising crops of culinary ex- 

 otics, as cucumbers, &c. ; in forcing common vegetables, as 

 asparagus ; in raising young exotics, as pines and other 

 plants; or in producing grapes. For the general purposes for 

 which pits are constructed, I shall beg leave to recommend one 

 invented by me, and erected on a small scale at Glenfuir; 

 which, with only one fire, is capable of producing four different 

 temperatures at the same time; and, consequently, of forcing 

 all kinds of common vegetables, and growing vines, pines, and 

 melons, each in their proper climate, with one fire and little 

 trouble or ex pence. It will be found described and fully deli- 

 neated in the Treatise on Hot-houses ; and some idea of its ap- 

 pearance may be formed from Plate XI. fig. 1., which is a sur- 

 face plan of it : a represents the cover of the excavation con- 

 taining the furnace; b the air registers, which assist in produc- 

 ing the different temperatures; c the air and steam tubes, 

 by which heated air is admitted from the rubble stone vacuity, 

 and steam produced by pouring in water, &c. Fig. 2. is a sec- 

 tion of this pit; which shews a the smoke flue; b the air flue; 

 € the chimney; d the supports of the rubble vacuity ; e the rubble 



