64 THE USE OF GLASS 



CONSTRUCTION OF FIRE HOTBEDS 



The essential features of a fire hotbed are a long sash-covered 

 frame underlaid by two flues connected with a fire-pit at one end 

 and chimney at the other. An ideal location for a fire hotbed is 

 a gradual slope to the south or east. Such a location insures full 

 exposure to sunlight, protection from cold winds, good draft for 

 the flues and drainage for the fire-pit. 



Fire hotbeds differ somewhat in details of construction. The 

 method of construction here described is in common use by truck 

 growers in southern Illinois. An area six feet wide and from 80 

 to 100 feet long is marked off in such a way that one end of the 

 bed will be a few feet higher than the other. A row of posts is set 

 along each side of this area, those on the north or west side extend- 

 ing eighteen inches above the level of the ground and those on the 

 south or east side twelve inches. These posts must be set about 

 two and one-half feet deep to prevent their being heaved out by 

 frost. The distance between the posts will depend upon the length 

 of lumber to be used in making the frame. For sixteen-foot lum- 

 ber, the posts should be placed five feet four inches apart. 



After the posts are set, boards are nailed onto the inside of 

 these rows of posts to make the walls of the bed. It is well to 

 allow the boards to extend two inches above the tops of the posts, 

 so that the latter will not interfere with the sash. 



The dirt should be dug out from between the walls to within 

 three iii^iches of the posts on either side. At the upper end of the 

 bed it is dug out to the depth of six inches, the depth gradually 

 increasing until the lower end of the bed is reached, where it is 

 two and one-half feet. The excavation is extended several feet 

 beyond the lower end of the bed. This extension is made one 

 foot narrower and one and one-half feet deeper than the bed 

 proper. Six feet of the upper part are to be used for the fire-pit, 

 the lower part being dug out for convenience in firing. The sides 

 of the pit are walled up with rock or brick to a height of two feet 

 and covered with broad flat rocks well supported by iron bars, 

 or the cover may be entirely of old boiler iron. 



From each side of the back of the fire-pit, a trench twelve 

 inches deep and nine inches wide is dug diagonally toward the 

 side of the bed. When within four inches of the side of the excava- 

 tion the direction is changed and the trench cut parallel with the 

 side of the bed. These trenches are covered closely with flat 

 stones to prevent dirt from filling them, The dirt which is first 



