180 GREENHOUSES 



Size of pipe Length of coil 



1 inch Up to 50 feet 



\Y 4 inch 50 to 75 feet 



iy 2 inch 75 to 100 feet 



2 inch 100 to 150 feet 



This table is based on the supposition that 

 gravity, only, is to be depended upon for 

 circulation. When pumps are used to cir- 



Fig. 96. Gasoline engine arranged to circulate hot water 

 in a greenhouse heating system 



