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 



50ft 100ft 200ft 300ft 400ft 500ft 600ft 700ft 



30 gal. per min. l]/ 2 2 2 2 2J4 2'/ 2J4 2*/ 2 



75 gal. per min. 2 2^ 2^ 2^ 3 3 3 3 



100 gal. per min. 2^ 2^ 3 3 3 3^ 3^ 3^ 



150 gal. per min. 2^ 3 3 3^ S*/ 2 3^ 4 4 



200 gal. per min. 3 3J4 3^ 4 4 4 44 



300 gal. per min. 3*< 3*4 4 4 4 4 5 5 



400 gal. per min. 44455556 



500 gal. per min. 45556666 



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, 



