IRRIGATION 
« 3 
The greater the pressure the finer the spray; but after 
reaching a certain pressure the spray is so fine that it 
retards the flow of water and reduces the distance of 
throw. It follows that when the pressure is so high as 
to produce these results, the lines must be installed 
slightly closer together, according to the preceding table. 
The preceding figures refer to pressure at nozzles. 
FIG. 1 8 . IRRIGATION SYSTEM INSTALLED AT THE 
PENNSYLVANIA STATE COLLEGE 
Figure 18 shows the overhead system in use at the 
Pennsylvania State College. A lever is provided at one 
end of each nozzle line, by means of which the entire line 
is easily turned. When in operation, the line is kept in 
one position until a strip of land has been sufficiently 
watered, and then the line is turned so the spray will fall 
on unwatered ground. It takes only a few seconds to 
turn each line and the attendant may be engaged in other 
