WATERING, HEATING, VENTILATING AND SHADING 161 
plants and beds. In effect it is like a very fine rain. If 
the beds have been properly prepared, the water will not 
stand on them and there will be practically no incrusta- 
tion on the surface of the beds, nor will the fine mist 
compact the soil. Again, there need be no fear of the fine 
mist causing mechanical injuries to the plants. 
(5) With the overhead system the hot, dry atmosphere 
of the greenhouse may be changed in a few minutes. 
This is often a great advantage in the summer for a crop 
like cucumbers. 
(6) It is also possible to apply fungicides, insecticides 
and liquid fertilizers through the overhead system of 
pipes and nozzles. 
The main flow or feeder line should run across the 
house, and it is usually most convenient to have it at the 
end near the boiler room or packing room. It should be 
amply large, to meet the demands of the houses. The 
following table, furnished by the manufacturers of a 
popular system, may be followed in determining the 
proper size of the main supply line: 
LENGTH OF LINE 
5Oft 100ft 2OOft 300 ft 400 ft 500 ft G00 ft 700 ft 
30 gal. per min. 1% 2 2 2 21% 2% 24% 24 
75 gal. per min. 2 2% 2A 2% : ‘ 3 3 
10@ gal. per min. 2% 24 3% 8% 8y 
150 gal. per min. 2% 3 8% 38Y% 38% 4 4 
200 gal. per min. 3 8% 38% 4 4 4 4 4 
300 gal. per min. ERA 3y% 4 4 4 4 5 5 
40@ gal. per min. 4 4 4 5 5 5 5 6 
500 gal. per min. 4 5 5 5 6 6 6 6 
Nozzles or distributing lines connect at right angles 
with the supply line. The connection is made with a 
patented swivel union, which makes it possible to turn 
the line with a lever, in order that all of the ground may 
be evenly watered. The nozzle lines are placed 16 feet 
apart, so that two lines would meet the requirements of a 
house 32 feet wide, three lines for a house 48 feet wide, 
etc. The nozzle lines may be 500 feet long if necessary. 
The size of the pipe will depend on the length of the line, 
