GLASS STRUCTURES. 



63 



crop to be grown. In the colder northern states, when the 

 hotbeds are made up at the beginning- of March, from 24 to 30 

 inches of manure should be used, and covered with six or- 



So^W 



Figure 24.— Cross section of hotbed, 

 eight inches of rich soil. Later in the season 18 inches or 

 even one foot of manure may be sufficient. In favorable loca- 

 tions, hotbeds may be run all winter for growing lettuce, 

 radishes, etc. This is not often practicable in the northern 

 states, and cheap greenhouses are generally used during 

 winter and hotbeds only during the spring. 



The hotbed frames for early spring- use, should be prepared 

 for the manure in the autumn. The soil for spring use should 

 generally be put into them, covered with leaves, and the 

 shutters and mats put on to keep out the frost. If this has 

 not been done, the sash may be put on in the early spring-, 

 which will partially thaw out the soil in the bed; or, by an- 

 other method, more manure may be used, putting- it on the sur- 

 face of the frozen land, and the frame may be set on top of it. 

 In the latter case the manure should extend at least one foot be- 

 yond the sides of the frame and be one-half again as deep as. 

 when placed in a pit, and the frame should be banked up 

 with manure. It is quite a common practice to make 

 movable frames of one inch boards large enough for three 

 or four sash, as shown in figure 23. These are kept from 

 year to year, being set on top of the manure and the 

 earth put into them. 



Hotbed Manure. — The material generally used for heating 

 hotbeds is fresh horse manure, but sheep manure and 

 even spent hops may serve the purpose. Of animal manures, 



