152 IRRIGATION FARMING. 



is construdled the measuring gate, while opposite to it 

 is a long overfall (C), the hight of which is used 

 to maintain a standard head above the measuring slot. 

 Such a weir is cheaply construdled and easily placed in 

 position, and costs but a few dollars for a small service 

 head. It needs no oversight or supervision, as it can 

 be locked until a change of volume is desired. The 

 irrigator himself can with his pocket-rule demonstrate 

 to his entire satisfa(5lion that he is getting the amount 

 of water in inches for which he is paying. 



Weirs. — To determine the flowing capacity of 

 small streams, ditches or laterals the redlangular weir, 

 such as is illustrated in Fig. 42, may be employed, 

 thanks to the ingenuity of James Leffel, of Ohio. The 

 illustration represents a weir dam across a small stream. 

 When it is convenient to use a vSingle board, as is shown 

 in the sketch, one may be selected sufficiently long to 

 reach across the stream, with each end resting on the 

 bank. Cut a notch in the board sufficiently deep to 

 pass all the water, and in length about two-thirds the 

 width of the stream. The bottom of the notch (B) in 

 the board, also the end of the notch, should be beveled 

 on the down-stream side, and within one-eighth of an 

 inch of the upper .side of the board, leaving the edge 

 almost sharp. A stake (£) should be driven in the 

 bottom of the stream, several feet above the board, on a 

 level with the notch (B) — this level being easily found 

 when the water is beginning to spill over the board. 

 After the water has come to a stand and reached its 

 greatest depth, a careful measurement can be made of 

 the depth of water over the top of stake (£), in the 

 manner illustrated. Such measurement gives the true 



