CHAPTER VIII. 



PITS AND FRAMES. 



§ 1. — PITS AND FRAMES HEATED 

 BY FERMENTATION. 



Op pits there is now a great variety, 

 adapted both for the cultivation of plants 

 and fruits. The most primitive struc- 

 ture of this kind appears to have been 

 a pit walled round with bricks, some- 

 times sunk under the ground-level, and 

 at other times raised above it, as the 

 situation was dry or damp. Upon this 

 was placed a wooden frame similar to 

 those still in use, covered with glass 

 lights, leaded or glazed in the casement 

 form, without astragals or overlaps. The 

 heat was obtained by filling the pit 

 with tanner's bark; but there were no 

 means of assisting it by linings, the use 

 of which was the next step in improve- 

 ment. 



At the time to which we have alluded, 

 pits were also heated by smoke flues, both 

 of bricks and earthenware cans. 



It is doubtful if, even in these days of 

 improvement, the use of fermenting mate- 

 rials will be entirely abandoned, as there 

 is something so congenial to the growth 

 of plants given out by the fermentation 

 of stable litter — probably ammoniacal gas, 

 accompanied with a suitable degree of 

 humidity in a warm state — which all our 

 other modes of heating, as at present em- 

 ployed, appear to come short of. This 

 is to be regretted; but we doubt not 

 that this defect will ultimately be got 

 over. Suggestions to this effect have been 

 noticed in the section Heating by Steam, 

 Tanks and Hot Water. 



In order to elucidate the relative merits 

 of pits, we shall begin with those heated 

 by fermentation, and include that section 

 of them denominated hotbed frames, 



which are no other than pits without 

 building appendages. 



The common hotbed frame requires no 

 description, being merely a bed of well- 

 fermented stable manure neatly put to- 

 gether, rather higher at the back than at 

 the front, upon which is placed the frame 

 and sashes, — the frame also being from 

 6 to 9 inches higher at the back than at 

 the front, with a view, no doubt, to place 

 the glass roof at a better angle of eleva- 

 tion to the sun's rays, and also to allow 

 the rain water to run freely off. 



The only improvement of any conse- 

 quence that took place in hotbeds and 

 frames, from the time of their being first 

 used up to the first quarter of the pre- 

 sent century, was that of forming the 

 ground on which they were erected upon 

 an inclined plane, equal to the angle of 

 elevation formerly given to the glass 

 roof. This was recommended by T. 

 A. Knight, with the view of equalis- 

 ing the bottom heat by having the dung- 

 bed of the same depth both at back and 

 front. The elevation being thus given to 

 the bed, the frame was then made of an 

 equal depth both at back and front. The 

 chief improvement next to that just no- 

 ticed was, constructing the frame with a 

 fixed bottom of deals, perforated so as to 

 admit of the escape of superabundant 

 humidity, but having the disadvantage of 

 preventing the heat from the dung-bed 

 from ascending. This was followed by 

 J. Weeks' patent forcing-frame, which is 

 no other than that suggested by Laurence 

 in his " Kalendar," published exactly a 

 century before. Its improvements con- 

 sist in putting a bottom of wire to the 

 frames, and covering that with tiles, 

 upon which the soil was laid ; the object 



