GLASS STRUCTURES. 



67 



made up at the beginning of March from 24 to 30 inches of ma- 

 nure should be used, and covered with six or eight inches of rich 

 soil. Later in the season 18 inches or even one foot of manure 



5 I i o 



Figure 25. — Cross section of hotbed. 



may be sufficient. In favorable locations hotbeds may be used 

 all winter for growing lettuce, radishes, etc. This is not often 

 practicable in the extreme northern states and cheap greenhouses 

 are generally used there during winter and hotbeds only during 

 the spring. 



The Hotbed and Frames for Early Spring Use should be pre- 

 pared in the autumn, so that no digging will have to be done in 

 the spring. 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 another method, more manure may be 

 used, putting it on the surface of the frozen land, and the frame 

 may be set on top of it. In the latter case the manure should ex- 

 tend at least one foot beyond 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 common practice to 

 make movable frames of one-inch boards large enough for three 

 or four sash, as shown in figure 24. 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 speni 

 hops may serve the purpose. Of animal manures, that from 

 horses fed on highly nitrogenous foods, i. e., on grain foods, wil: 



