GATE STRUCTURES FOR IRRIGATION CANALS. 49 
AUTOMATIC CHECK GATE, TURLOCK IRRIGATION DISTRICT. 
The Turlock irrigation district of California is using for all new 
constructions and all replacements of worn-out wooden checks a pat- 
ented automatic gate, which holds the water above it to a constant 
level (fig. 14). 
The essential features of this check are: A wooden-faced gate 
with wood or iron radial arms attached to an axle shaft; a concrete 
well cast in one wing of the structure, with an inlet pipe from the 
water whose level it is desired to hold constant ; an outlet pipe emerg- 
ing from near the bottom of the well into the water below the check 
gate. The level of the water into which the outlet pipe discharges 
must be lower than the level of the water which the device is to hold 
constant; a tank float in the well (D) (PL X, fig. 1), hung by a 
chain to the end A of lever 2, which is connected to lever 1 at B. To 
the end O of lever 1 is attached the chain lifting the radial gate. The 
fulcrums of the levers are placed at the centers. A counterweight 
(E) of concrete is hung from the intersection of the two levers at B. 
The tank is partially filled with water, the amount adjusted to fit 
each gate after it is in operation. 
The operation of the gate is as follows: Assuming there is no 
water in the canal and the gate (G) is shut, the free end of the inlet 
pipe (P) is placed at the level to which it is desired to hold the 
water, the free end of the outlet pipe being placed lower than the 
opening in the inlet pipe. As the water comes down the canal the 
closed gate causes it to rise until it enters the well through the inlet 
pipe. As it rises in the well the weighted bucket or tank is floated, 
the levers at B are both pulled down by the counterweight, and the 
gate lifted, allowing water to pass under it, establishing equilibrium 
again. The water in the well flows out slowly through the outlet 
pipe, tending to lower the tank, raise the weight at B, lower the gate^ 
raise water above the gate which flows into the inlet pipe, and thus 
keep up a circulation of water in the well. It requires about an 
8-inch head of water on the gate for it to adjust automatically. 
If water has been running in the canal several days, always main- 
tained at the same elevation, and an unexpected rise in the water 
occurs, the depth of water above the gate increases rapidly, submerg- 
ing the inlet pipe and quickly raising the water in the well, which 
as quickly lifts the float, lowers the counterweight, and raises the 
gate to allow the unexpected volume of water to pass by until equi- 
librium, is again established, always at the level of the opening to the 
inlet pipe. 
In the same way, if the volume in the canal is diminished, the 
water level falls below the opening in the inlet pipe, the water in 
the well lowers gradually through the outlet pipe, the tank settles 
