APPENDIX 



in the case of artesian waters, which flow out of the mouth of 

 the well by reason of their own pressure. 



The principal difference between securing a supply for do- 

 mestic and for agricultural purposes is that in the case of the 

 former the water must be as pure as possible, while in the 

 case of the latter the impurities which gather in ponds and 

 streams have a distinct commercial value as fertilizers. The 

 sewage of Paris is used for irrigation purposes with wonder- 

 ful effect. The same thing is done at Los Angeles, and 

 doubtless will be done in many places hereafter. Neither is 

 it necessary, as a rule, to make such elaborate provision for 

 the distribution of water through underground pipes in the 

 case of agriculture as in that of domestic water supply. In 

 the vast majority of instances irrigation water flows in open 

 channels. Where it is otherwise it is because the precious 

 fluid is scarce, and therefore dear, so that every drop must be 

 guarded against loss by evaporation or by seepage into the 

 ground. 



Irrigation works in the West range from rude and simple 

 ditches, taking their supplies from mountain brooks where 

 the water has been diverted by means of small brush dams, to 

 great masonry walls which block the outlet of deep canyons, 

 holding back the water, which is transported through pipes, 

 flumes, and cemented ditches to rich lands miles away. In the 

 one case the works have been constructed by a small association 

 of farmers, using their own labor and teams ; in the other, 

 millions of eastern and foreign capital have been invested. 

 In both cases the water is led through main canals to central 

 points in the territory to be reclaimed. These mains are of 

 all sizes, depending entirely upon the volume of water re- 

 quired. They are frequently not more than six feet wide, 

 though some of the canals in the San Joaquin Valley are one 

 hundred and twenty feet in width. From these mains lat- 

 eral ditches reach out in various directions. The individual 

 farmer taps the lateral with a shallow ditch, usually made 



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