204 Description of various Modes of Heating by Steam. 



3. For Green-houses, one square foot is equal to 200 feet. 



N. B. Houses that are ill glazed, or placed .in an exposed situ- 

 ation, may require an addition of ten or fifteen per cent to the pro- 

 portionate surface of the boiler. 



The surface of the fire-grating should be from one-fourth to one- 

 fifth of the bottom surface of the boiler, according to the strength of 

 the fuel employed. 



Mr. Miller s boilers present a bottom surface of about thirty- 

 three feet each, being nine feet long, by three feet seven inches wide. 

 The fire-grating is two feet four inches wide by three feet long. 

 These two fire-places are found effective in the severest weather. 



