150 



IRRIGATION. 



cessive portions. It consists in supplying an earthen or 

 wooden pipe, which is set perpendicularly in the ground 

 in the line of the main drain, so that the main drain 

 pipe enters it upon one side, and leaves it upon the other. 

 This pipe thus cuts the main drain at such intervals as 

 may be desirable. It is covered by a cap, and is reached 

 through a covered trap or box, placed on a level with the 

 surface of the ground. This is seen at fig. 76. The 



proper situations for these 

 pipes are just below the junc- 

 tion of a series of lateral drains, 

 as at d, d, in fig. 75. These 

 pipes offer facilities for closing 

 the drain by means of simple 

 contrivances. The most ef- 

 fective of these is a plug or 

 cushion of wood, which fits 

 in the drain leading from 

 the pipe or well. This plug 

 is fastened horizontally to 

 the lower portion of the T- 

 shaped arm. One of the up- 

 per cross parts of the T is fixed into a hole or groove in 

 the pipe or well, and a wire i's fastened to the other cross 

 part. When the wire is pulled, it moves the lower por- 

 tion of the T laterally, and draws the plug from the 

 opening of the drain pipe. When the wire is released, 

 the weight of the arm of the T carries the plug to its 

 place again, or the force of the water flowing through 

 the drain carries it and holds it there. This is shown in 

 fig. 76, in which A, B, is the drain pipe ; #, the box or 

 trap by which the wire is reached ; 5, the plug with its 

 movable arm, from which a copper wire is carried to the 

 upper box, where it is secured by a ring upon a hook. 



The operation of the contrivance is as follows : When 

 the drain is closed and the flow is stopped, all the drains 



Fig. 76. PLUG FOB CLOSING 

 DRAIN. 



