I30 IRRIGATION FARMING. 



the woodjvork joins upon the earth orterreplein, as the 

 case may be. There the earth should be carefully pud- 

 dled at the apron and the whole surface from . side to 

 side of the ditch, and the sides as well, should be tamped 

 and retamped. Retaining walls or riprap at the sides 

 and embracing the flaring wings may be employed, but 

 in any event the tamping must be thoroughly done and 

 the work gone over time and again if needs be in order 

 to prevent the possibility of washing out. This tamp- 

 ing will be necessary if either the drop-box or the 

 inclined apron be used. 



The bracing of a flume is an important matter, 

 especially with deep flumes. A good system of side 

 bracing is depidled in the bridge flume across a stream, 

 and shown in Fig. 31. 



Cross-secftion braces are often made with iron rods 

 running through the side posts and tightened with nuts 

 and washers. Any builder can arrange the matter of 

 the bracing to suit himself. 



In very high flumes a lofty trestlework may be 

 required. If this is the case it is better to build the 

 bents in sedlions on the ground and then raise them 

 into position by means of tackle-blocks and a windlass, 

 or by using a steam hoisting drum if the same may be 

 readily obtained without much expense. -The modus 

 operandi of hoisting these great trestle sedlions is clearly 

 illustrated in Fig. 32, which is a scene taken by photo- 

 graph during the constru<5lion of a high flume near San 

 Diego, California. As a general rule such strudlures 

 as this are not pradlicable. 



The great bench flume on the High-Line canal in 

 Colorado is illustrated in Fig. 33. This flume is 



