362 



A CCELERATINQ VEQETA TION. 



Ashes, Tan, and Leaves. Ashes are often mixed with the dung of 

 hotbeds, and are supposed to promote the steadiness and duration of 

 their heat, and to revive it if somewhat decayed. Tan and leaves 

 have also been used for the same purpose ; and it is generally found 

 that about one-third of tan and two-thirds of dung will form a more 

 durable and less violent heat than a bed wholly of dung. The heat of 

 dung-beds is revived by linings, or collateral and surrounding walls, 

 or banks of fresh dung, the old dung of the bed being previously cut 

 down close to the frames. These linings, as before observed, require 

 less preparation than the dung for the beds. The dung-bed being 

 formed, and having stood two or three days with the frame and lights 

 placed over it to protect it from rain, is next to be covered with 

 earth, of such quality and quantity as the purpose to which it is to be 

 applied requires. In severe weather, the sides of the bed are often pro- 

 tected by hurdles of straw or faggots, which tend to prevent the escape 

 of heat. 



The nightly covering to hotbeds and pits may be of boards, or of 

 bast-mats, or reed or straw mats ; and the following mode of securing 



the covering will 



Fi S- 329 ' be found neat as 



well as econo- 

 mical : Three 

 pieces of iron of 

 the form of fig. 

 329, a,are screwed 

 on to the end of 

 the frame, one 

 piece at the top, 

 another at the 

 bottom, and the 

 other in the mid- 

 dle, so that the top of the iron is about two inches above the light ; 

 on the opposite end three pieces of the form of c, are screwed on at the 

 same distances as a ; b is a side view of a, and d is a side view of c. 

 A wire, three-eighths of an inch in diameter, and rather longer than 

 the frame it is intended for, must be made with a loop at one end (/) 

 to place over the iron d ; the other end must be fitted with a thumb- 

 screw (e), to screw up the wire when it is placed in the notch g, which 

 should be countersunk in the centre. Small hooks should be driven in 

 the frames, either in front or back, to lay the wires in when not in use. 

 A much simpler and more common method is to lay a piece of wood 

 of sufficient height on to the front and back of the frame. 



Management of Hotbeds and Pits Heated by Dung. As the body of 

 air enclosed is small, its temperature is easily raised too high by the 

 sun, and depressed too much by high winds or very cold nights. The 

 artificial supply of heat from the fermenting material not being under 

 control is another cause of overheating, and hence the constant atten- 

 tion required to give or take away air during the day, and to regulate 

 the coverings put on at night. Much mischief is produced by over- 



V 



Details of wire-fastening mats on frames , one- sixth 

 of the full size. 



