18 GREENHOUSES 



cient. The manure will continue to give off 

 heat for three to six weeks. 



The dimensions are determined by the 

 sash. Since sash are 6 feet long and are con- 

 structed to slope lengthwise rather than 

 crosswise, the width of the pit north and 

 south should be a trifle less than 6 feet over 

 all. The length is determined by the num- 

 ber of sash desired. Since they are 3 feet 

 wide, it should be some multiple of three. 

 For example : A two-sash bed would be 6 x 6 

 feet, a three-sash bed 6x9 feet, etc. It is 

 essential that the pit be well drained either 

 naturally or artificially. If it is to be used in 

 early spring, it is made the previous fall, 

 filled with straw or manure and covered with 

 boards to keep out rain and snow. When 

 the bed is to be made this material is re- 

 moved, leaving an unfrozen pit in which 

 the new manure will heat more evenly and 

 be more efficient. 



The upper or north side of a permanent 

 hotbed is preferably 6 or 8 inches higher 

 than the south side to give the proper 

 slant to the sash. The north side may be 

 about 15 inches and the south side about 9 

 inches above the surface of the soil. The 

 sides are connected with crossbars placed 



