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THE POPULAR SCIENCE MONTHLY 



A typical sandy waste. The cross and arrow indicate one of the pipe-lines which 

 carry water to the coast from the Andine streams. 



ent salty compounds, and as evaporation still continued, the different salts 

 began to deposit on the pampa, in the salitreras and salares, much as 

 the}' are to-day. Then as a final step sand and rock fragments from 

 neighboring hills covered the beds with their present capping of loose 

 waste. 



Other explanations of the origin of the nitrate have been advanced. 

 One ascribes it to natural chemical processes accompanying decompo- 

 sition of different minerals. Another suggests that the wonderful elec- 

 trical discharges in the Andes are responsible, for the odor of nitric acid 

 in the air is not uncommon after severe electrical storms, and electricity 

 even now is being used to extract nitrogen from the air. But the enor- 

 mous amounts of nitrate in Chile and the geological conditions of its 

 occurrence fit in best with the idea of origin from guano, as stated above. 



The fertilizing value of these nitrates is supposed to have been known 

 to the Peruvian Incas, but not generally to have been taken advantage 

 of by them. Tradition also says that Bolivian Indians at an early date 

 came down from the plateau after nitrate to use on their crops, and it 

 credits them, rather doubtfully, with having developed a primitive form 

 of refining. Bich pieces of caliche, so the story runs, were boiled with 

 water in great earthen pots, called cachuchos, after which the solution 

 was allowed to cool and evaporate until crystallization of nitrate re- 

 sulted. Fairly pure nitrate can be secured in this way. Some of the 

 earliest manufacturers for commercial purposes are said to have fol- 

 lowed almost the same method, and the principle is exactly like that of 

 the modern process. Even the name " cachuchos " still persists, though 

 the great steel or iron boiling tanks of to-day scarcely suggest 

 " earthen pots." 



Prior to the nineteenth century the outside world knew little or noth- 



