64 The Principles of Vegetable Gardening 



to put in a hot water or steam heater for the express 

 purpose of heating hotbeds, for if such an expense is 

 incurred, it will be better to make a forcing -house. 



Flue-heated beds. Hotbeds may be heated with hot 

 air flues with very good results. A home-made brick 

 furnace may be constructed in a pit at one end of the 

 run and underneath a shed, and the smoke .and hot 

 air, instead of being carried directly upwards, are 

 carried through a slightly rising horizontal pipe which 

 runs underneath the beds. For some distance from 

 the furnace, this flue may be made of brick or unvit- 

 rified sewer pipe, but stovepipe may be used for the 

 greater part of the run. The chimney is ordinarily at 

 the farther end of the run of beds. It should be 

 high, in order to secure a good draft. If the run of 

 beds is long, there should be a rise in the underlying 

 pipe of at least one foot in twenty -five. The greater 

 the rise in this pipe, the more perfect will be the 

 draft. If the runs are not too long, the underlying 

 pipe may return underneath the beds and enter a 

 chimney directly over the back end of the furnace, 

 and such a chimney, being warmed from the furnace, 

 will ordinarily have an excellent draft. The underly- 

 ing pipe should occupy a free space or pit beneath the 

 beds, and whenever it lies near to the floor of the bed 

 or is very hot, it should be covered with asbestos 

 cloth. 



Glazing. The most satisfactory glass for use in 

 hotbed and coldframe sash is double -thick, second- 

 quality grade; and 12 -inch panes are ordinarily wide 

 enough, and suffer comparatively little in breakage. 



