PLATE i 
The effect of aluminum sulphate on the penetration of irrigation water. The plat 
at the right was treated with aluminum sulphate at the rate of 5 tons per acre, but the 
plat at the left was not treated. Both plats were given the same quantity of water. 
Photographed 54 hours after the water was applied; Sacaton, Ariz., November 18, 
1921. 
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