160 GREENHOUSES 



plants near them are less likely to be injured 

 than when 'steam is used. (3) It requires 

 less frequent firing, since warm water is al- 

 ways circulating in the pipes as long as there 

 is any fire in the furnace, whereas, with 

 steam it is necessary to keep the water boil- 

 ing to keep steam in the pipes. (4) For the 

 above reason a night fireman is not required 

 in small houses equipped with hot water. (5) 

 It is less dangerous. This is more apparent 

 than real, for steam is usually carried at low 

 pressure. (6) It is claimed that hot water 

 requires less fuel. Theoretically this should 

 be true, but in practice it has not been very 

 definitely proven. (7) Water will hold heat 

 for some time if the fire should accidentally 

 go out. 



The following advantages are claimed for 

 steam: (i) Less cost of installation. (2) 

 Steam requires fewer radiating pipes hence 

 less shade is cast when the pipes are placed 

 overhead than when hot water is used. (3) 

 Less time is required to get up heat, as there 

 is a relatively small body of water. (4) A 

 greater area may be warmed from a given 

 heating plant than with hot water, for the 

 steam may be forced farther. (5) A steam 



