VEGETABLE GARDENING 
84 
work, making the rounds of the pipe lines as often as 
may be necessary. Automatic oscillators, such as the 
one shown in Figure 17a, may be installed, and will re- 
sult in a further saving of labor, since the usual atten- 
tion to change the direction of the spray is no longer 
needed. Such an apparatus depends for its action en- 
tirely on the water pressure in the line. Some of the 
water is diverted from the vertical feed pipe through a 
water wheel ; this wheel operates a series of cog wheels, 
which turn the irrigation pipe back and forth over the 
area to be watered. If watering is attended to systemati- 
cally, it is probably never desirable to apply more than 
an inch of water at a time. The numerous bulletins is- 
sued by the manufacturers of overhead irrigation equip- 
ment give additional details concerning the installation 
and operation of these systems. 
FIG. I/A. AUTOMATIC OSCILLATOR FOR OVERHEAD 
IRRIGATION SYSTEM 
A and B, valves; C, water wheel; D chain of gears; E. eccentric; 
F. pendulum; G, gear; T. connecting pipe; J, union; K. hook 
