164 



PRINCIPLES OF HEATING HOT-HOUSES. 



as much from the frame as from the glass ; therefore no deduc- 

 tion is required in such cases. 



From the preceding calculations the following corollary may 

 be drawn : 



The quantity of air to .be warmed per minute in habitable 

 rooms and public buildings, must be 3^ cubic feet for each 

 person the room contains, and l cubic feet for each square 

 foot of glass. 



For conservatories, forcing-houses, and all buildings of this 

 description, the quantity of air warmed per minute must be l 

 cubic feet for each square foot of glass the structure contains. 



When the quantity of air required to be heated has thus been 

 ascertained, the length of pipe to heat it by hot water may be 

 found by the following table : 



Table of the quantity of pipe 4 inches diameter which will heat 1000 cubic 

 feet of air per minute, any required number of degrees. The temperature 

 of the pipe being 200 Fahrenheit : 



To ascertain, by the above table, the quantity of pipe required 

 to heat 1000 cubic feet of air per minute, find, in the first column, 



