Dr. William Newton — Origin of Nitrates in Chili. 339 



II. — The Origin of Nitrate in Chili. 

 By Dr. William Newton, F.I.C., F.C.S. 



FROM the first discovery of nitrate in these provinces it has been 

 an interesting question as to what caused it to come into exist- 

 ence here in such abundance, and, as far as our present knowledge 

 goes, nowhere else in the world in such quantities. 



Many theories have been formed attempting to explain the presence 

 of these deposits of nitrate ; the most popular, and a theory also 

 accepted in scientific works, being, that in past ages the nitrate 

 pampas were sea-beaches, and that an enormous quantity of sea- 

 weed was piled up on them. In course of time these beaches were 

 elevated above sea-level and the seaweed decomposed, leaving its 

 nitrogen in the state of nitrate and its small quantity of iodine as 

 iodate. 1 



Darwin suggests tbat the plain of Tamarugal was either a lake or 

 an arm of the sea. If it were an arm of the sea, he at once jumps 

 his previous estimate of 400 feet elevation of the coast of Peru to 

 3,000 feet and over. The sea-shells which he notes are only found 

 with caliche (the raw nitrate) in one or two places where tbe nitrate 

 bed is in contact witb the Chalk, and are evidently tbe remains of 

 organisms from that formation. It is unfortunate that in the great 

 naturalist's short visit to the nitrate districts, he was apparently not 

 informed of the periodical floods which come down from the 

 Cordilleras on an average about every seven or eight years, and 

 flood the whole of the plain for a short time. 



The present surface soil of the pampa is evidently due to the silt 

 carried by these floods, and as far as borings have gone the under- 

 layers of alluvial, and, indeed, the whole filling up of the valley, are 

 due to the same periodical action. 



Apparently the plain has never been the bed of a lake, at any rate 

 in geological times commensurate with the soluble surface deposits, 

 unless these occasional floods can be called lakes. 



The origin of this sea and seaweed theory is chiefly due to the 

 fact, that previous to the time of producing iodine from nitrate 

 liquors, the only source of iodine was •' kelp," the ash of burnt sea- 

 weed. The decomposition of seaweed, as also all organic matters 

 under certain circumstances, does produce nitrate. The presence of 

 lai'ge salares on the pampas, in proximity to the nitrate, also gives 

 colour to the idea of the former presence of the sea. 



But. one must bear in mind that even the salt of the sea is derived 

 originally from the washings of the land. There is no more reason 

 to suppose the salares are evaporated sea- water than that any of the 

 inland salt lakes of the world were originally connected with the sea. 

 Inland salt lakes derive their salt from the washings of the soil sur- 

 rounding them. The water running into the lakes may not be very 

 salt, but if there be no outlet from the lake, the constant evaporation, 

 especially in hot climates, gradually concentrates the salt in them, 

 sometimes all the water being evaporated and only a salar left. 



1 Darwin's " Naturalist's Voyage" ; Watts' " Dictionary of Chemistry, etc." 



