CANAL CONSTRUCTION. 53 



placed at a point convenient to discharge water back to 

 the river through the waste and sand gates. The use of 

 piling is necessary in soft ground, although some builders 

 continue to put in mudsills and depend upon stone an- 

 chorage to keep the structure in place. The writer 

 would advise wings to be put in on each side of the 

 gates, where there is no rock in place, and these wings 

 should extend in either direction and especially on the 

 lower side, if the surface of the land be flat for a distance 

 of from fifty to one hundred feet. 



We have of ten seen headworks left standing 'alone 

 in the middle of a torrent of water after a heavy storm, 

 and have noted that the damage of the washout might 

 have been averted had wings of piling or masonry been 

 put in. The superstructure should be built of heavy 

 timber and provided with a windlass. It is a good plan 

 for large canals to have the gates arranged in stalls, each 

 working independent of the other. A gate of modern 

 construction is shown in Figure 11, the lower end in view 

 wit h water passing through. It fortunately is anchored in 

 rock walls and is not supposed to wash out, nor does it 

 need the protection of wing pilings. 



In Scott's Bluff county, Nebraska, the Nine Mile 

 canal has its headgate 900 feet below the intake, which 

 is at a seepage basin formed by damming up a channel 

 in a river at the side of an island. The dam is located 

 above the mouth of the canal, while the channel or basin 

 is left open with the idea that the backwater from the 

 river will flow in at the lower end of the island, and in 

 this way there will be but little sand with which to con- 

 tend. The plan has many features to recommend it, but 

 it could be adopted only in the situations favorably lo- 

 cated as to the island and with a moderate fall of the 

 stream at the desired point. 



