1 42 THE POPULAR SCIENCE MONTHLY 



The source of these deposits is a subject which has given rise to a 

 great deal of discussion. Many theories have been advanced to account 

 for the origin of the nitrates, but all appear to fall short of adequately 

 accounting for all the conditions under which the nitrates are found in 

 Chile. It is generally considered that an organic source is the most prob- 

 able, but there have not been lacking explanations for the formation of 

 these nitrates which have been based on inorganic agencies. 



Thus one of the theories advanced is that the nitrates may have re- 

 sulted from electric storms occuring in the Andes. It has been suggested 

 that the nitric acid which is formed in this way by the oxidation of the 

 nitrogen of the air becomes changed into calcium nitrate on coming in 

 contact with the limestone of the mountains, and that this in turn on 

 being washed down into the pampa region has been converted into 

 sodium nitrate in coming in contact with the sodium salts already exist- 

 ing there. It has also been stated that at certain seasons of the year 

 there is a great deal of static electricity in the air over the desert region, 

 owing to the strong winds and the extremely dry climate, and that the 

 nitric acid which is formed as a result of this condition is carried to the 

 ground by the moisture in fogs which drift in from the sea. 



The view has also been advanced that the nitrogen in the Chilean 

 nitrate may have come from nitrogenous fumes given off by volcanoes in 

 the Andes. It has already been pointed out that nitrides and ammonium 

 salts are sometimes found in the vicinity of volcanoes after an eruption, 

 but whether these compounds result from the direct fixation of atmos- 

 pheric nitrogen near the mouth of the volcano, or from some combined 

 form of nitrogen already present in the earth is not known, but the 

 former view is the more probable. It has been shown, however, that the 

 source of the nitrogen is not organic. 



It has been claimed by some that alkali carbonates are able to bring 

 about the fixation of atmospheric nitrogen into nitric acid in the presence 

 of oxidizable matter, and Pissis 6 expressed the opinion that the niter 

 beds in Chile were formed in this way. It was pointed out that the 

 decomposition of feldspar rock in the region of the Andes supplied alkali 

 carbonates, while the protoxide compounds of iron which are common in 

 the rocks of the pampa are easily oxidized under ordinary conditions to 

 form peroxide compounds of iron. The view was accordingly put for- 

 ward that the alkali carbonates in contact with rocks of this kind brought 

 about the oxidation of the nitrogen of the air with the ultimate forma- 

 tion of nitrates. 



Perhaps the most far-fetched attempt at an explanation of the origin 

 of these deposits was that presented by a writer 7 in the Comptes Rendus 



6 ' ( Nitrate and Guano Deposits in the Desert of Atacama, ' ' A. Pissis, Lon- 

 don, 1878. 



7 Bordas, Compt. rend., 147, 924, 1908. 



