lo Feb., 1911] 



Irrigation. 



■J \>r^2' 



structures, and, seeing that as yet no meter has been produced to satisfy 

 practical requirements, it is doubtful if the expense is justified. Outlet 

 boxes made as shown in drawing No. 59 are 

 effective and cheap. They are usually so 

 located that they are not called upon to bear 

 heavy traffic, and the timbers used in their 

 construction need not exceed 2 inches in thick- 

 ness. Where so great an area of waterway 

 is required as to necessitate the use of more 

 than single planks, collars as shown in sec- 

 tional drawing No. 58 will give strength and 

 act as flanges to check any tendency there may 

 be for water to creep along the sides. 



If the ground is very sandy the width of collars can be increased by 

 adding extra boards. The length will be governed by local circumstances. 

 Shutters may be of similar design as for culverts (.see No. 57), or, pre- 

 ferably, as in drawing No. 59. Being set at an angle they are more readily 

 operated from bank of channel, make a closer joint, and the earth stopping 

 lies up better to them. Outlets of this description, if well rammed, will 



Cross Sec /■ I on 

 ;8. OUTLET BOX. 



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OuNet Bo/ 



Cross 



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yhutter for Jo 

 Sectiom 



Section f\ B 



59. DE.SIGN FOR CHEAP OUTLET BOX. 



rarely wash out. In designing outlet boxes, it is desirable that the greatest 

 dimension shall be width, for the reasoii that more water may be available 

 when a supply channel is low. than if the principal dimension was depth : 

 and all outlets should deliver water unrlerneath the shutter or regulating 



I 



J 



3ed of outlet- 



61. MOVEABLE BAR.S. 



Bed of ooHpf 



60. MOVEABLE SHUTTER. 



bars. If bars or shutters are set t<> take water ovir the top, the suppK 

 chaiuiel nuy fall so low that no water ran be delivered, whereas, with 

 underflow, the last drop in the channel may be utili/i-d. ;is shown in dr;i\\ 

 ings Nos. 60 and 61. (To he continued .) 



