Heating with Pipes and Flues 



351 



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218. Pipe-heated hotied. 



underneath the beds. The pipes should not be surrounded 

 by earth, but should run through a free air space. 



A flue-heated or pipe-heated hotbed may be likened to a 

 greenhouse bench, and the arrangement of piping for the 

 two should be similar. 

 Two to four steam- or 

 water-pipes are carried 

 underneath the bed. If, 

 however, one has plenty of 

 exhaust steam, which is 

 usually under consider- 

 able pressure, it may be 

 carried directly through 

 the soil in ordinary drain 

 pipes. It will rarely pay 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 con- 

 structed in a pit at one end of the run and underneath a 

 shed, and the smoke and ho^ air, instead of being carried 

 directly upwards, are carried through a slightly rising 

 horizontal pipe which runs undernteath the beds. For 

 some distance from the furnace, this flue may be made of 

 brick or unvitrified sfewer pipe, but stovepipe may be 

 used for the greater part of the run. The chimney is 

 ordinarily at the farther end of the run. It should be 

 high, to provide a good draft. If the run of beds is long. 



