476 TVVI^NTV-EIGHTH ANNUAL REPORT 



accompanied by very high permanent hardness. In November and 

 December the temporary hardness ("lime") increased to double the 

 average for the other months of the year, which had been nearly 

 uniform. 



Fluctuations during 1916, when the total solids were decreas- 

 ing rapidly, were explained, apparently, by the opening of new 

 drainage areas as the work on the ditch progressed. The present 

 fluctuations are less easily explained but are probably due to 

 changes in the amount of seepage from various areas according to 

 the amount of irrigation, and also to overflow reaching the ditch 

 which would tend to dilute the usual seepage flow. At no time has 

 the drainage water been entirely satisfactory for irrigating purposes 

 on account of its high salt content. At times when the salt is ex- 

 cessive, as was the case in September, the water should not be 

 applied to agricultural lands. The high black alkalinity in Decem- 

 ber would be dangerous if long continued, but the usual gypsum 

 content of the water would serve to neutralize the occasional black 

 alkaline flows. It is possible that a correlation between the dis- 

 tricts receiving heavy irrigation and the character of the drainage 

 ditch water could be worked out for the purpose of avoiding the use 

 of excessively saline seepage water on the Indian Reservation lands 

 below, that are being irrigated with this water. A simple volu- 

 metric test for chlorides is available and should be applied at fre- 

 quent intervals by some person in the immediate vicinity. Waters 

 above the average in salinity should be allowed to waste. 



NATIVE FERTILIZER MATERIALS 



The prevailing high prices of fertilizer materials, especially of 

 nitrogen and potassium, has stimulated the search for these sub- 

 stances in the State. The deposits of bat guano have been drawn 

 upon quite heavily for exportation. The discovery of nitrate of 

 soda or Chili saltpetre in some of the rocks of the State has awak- 

 ened much interest. The cliemist visited one of these deposits 

 near San Simon and secured samples for analysis. The rock, whicti 

 is a rhyolitic tufa, is often covered with incrustations one-half inch 

 thick, more or less, of nearly pure nitre where overhanging ledges 

 protect it from the weather. The rock itself shows a few tenths 

 percent of nitrate of soda, but occasionally very thin seams of the 

 nearly pure salt occur. A tunnel driven ten feet into the ledge did 

 not develop richer material. Recently a sample of similarly in- 

 crusted rock has been sent in from another part of the State, but 



