104 



IRRIGATION FARMING. 



of the water both cemented and puddled it there. 

 Immediately above the site the banks of the stream 

 separate so as to include a reservoir of a somewhat oval 

 shape 1 ,600 feet long and 500 feet in average width, and 

 of an average depth of 30 feet. As shown by the cross- 

 seaion in Fig. 21, the dam is 85 feet in hight at the 

 middle of the stream and is 300 feet wide at the bottom. 

 Its entire length is over i ,000 feet. Its careful construc- 

 tion and the precautions taken to render the dam 

 impervious to water are shown by the cross-sedlion. 



« K) io y> to V ' 





FIG. 21 — CROSS-SECTION OF HYDRAULIC RESERVOIR. 



Under the upper half of the dam the excavation is 

 made to bed-rock; parallel strips of bed-rock surface 

 are broken fresh, and concrete ribs built thereon 

 parallel with the center of the dam. In these concrete 

 ribs, in the composition of which the very best 

 hydraulic cement is used, triple sheet piling is embed- 

 ded and carried up into the puddle. The entire upper 

 half of the dam was puddled and spread in thin layers, 

 and each day a herd of goats was driven onto the 

 bank and kept moving the entire time. There is three 

 feet thickness of quarry-broken riprap on the upper 

 side to protedl the dam from ac5lion of the waves. 

 Where the creek channel passes under the dam a semi- 

 circular arch rests on bed-rock to carry off any sudden 



