METHOD OF HEATING 169 
house to be heated, from five to eight or nine inches 
in diameter, the latter being sufficient for a house 
60 by 21 feet. The flue should be raised a little 
from the ground, and at no point should any wood- 
Fig. 8—Hot water is undoubtedly the most sat- 
isfactory method of heating the small green- 
house. The diagram shows a I-inch supply 
pipe leading out from the boiler, with 1-inch 
returns under the benches, making a satisfactory 
system for the lean-to type described in detail 
in the previous chapter. 
work be nearer than six inches to it. Very small 
houses, especially if not started up until January, 
may be heated by an ordinary wood stove with the 
stove pipe run the length of the house, but such an 
arrangement will give off a very drying and uneven 
heat, and require a lot of attention, to say nothing 
of its danger. 
