CONSTRUCTION OF GREENHOUSES 
125 
build with a space of to to 15 feet between the houses. 
This not only renders gutters unnecessary, but avoids 
shading in the houses and gives room for snow. 
180. Glass. — It is most economical in the end to use 
glass of high quality. Single strength was in common 
use 10 or 15 years ago, but experience has taught green- 
house men that anything inferior to A double strength 
FIG. 28 . A COMMON FORM OF GREENHOUSE BRACING 
should not lie used. The lighter and inferior grades not 
only sustain greater breakage from hailstones, but the 
imperfections may cause injury to the plants by burning. 
Small glass was used extensively in the construction 
of the old-style houses, which necessitated placing the 
sash bars close together. This condition increased the 
cost of construction and decreased the amount of light 
that could enter. For many years 10 x 12-inch glass was 
