248 



IRRIGATION. 



iron plate in the sill and a cast-iron shoe upon the gate. 

 A common mode of construction is as follows : The gate 

 slides in side quoins ; a flat bar supports an upright frame, 

 in which a toothed-wheel is fitted, gearing into the rack 

 of the stem of the gate. By turning the toothed-wheel 



f. 131. A LEVER-GATE. 



by a crank, the racked stem is raised or lowered, and the 

 gate with it. At fig. 130, a form of sluice worked by a 

 screw, a, passing through a projecting eye, b, in the 

 gate, /, and a revolving nut, c, and lever- wheel, e, in the 

 frame. By turning the lever-wheel the gate is raised. 

 Another form is shown at fig. 131. The gate is lifted by 



an arm a, which works on 

 a pivot, and catches into a 

 rack on a quadrant 5, and 

 is there held, keeping the 

 gate open at any desired 

 hight. A very common 

 wooden stop is shown at 

 fig. 132. This is suitable 

 for small channels, and is 

 made of two boards joined 

 together, but separated at the ends, as shown at a, a. In 

 the space between the boards a sluice board, , is passed, 

 being lifted by a hand-hole, and kept at any point by a 

 wedge, c. An aperture is made in the boards of a size 

 required, the lower edge being level with the bottom of 

 the channel. 



Fig. 132. HAND-GATE. 



