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



Salares are also formed by the water below the surface of the soil 

 being drawn up by capillary attraction and constantly evaporated, 

 giving place to fresh supplies and evaporation. 



To the seaweed theory of the formation of nitrate there are at 

 least three insurmountable objections. The first is that seaweed 

 contains bromine as well as iodine. Most of the caliche in this 

 province does not contain bromine, as it would have done if it were 

 derived from seaweed. There is no process in nature which could 

 completely separate bromides from a mixture of iodates, chlorides, and 

 nitrates. Secondly, there are seldom sea-shells or other sea debris 

 in or near the nitrate deposits. There would necessarily be these if 

 it had been a sea deposit. Thirdly, the stones in the caliche and its 

 neighbourhood are sharp and jagged, showing no signs of being 

 water- worn, as they would do if they had existed on a sea-beach. 



There is another suggestion which finds much favour — that is, that 

 nitrate may have been derived from the decomposition of ancient 

 guano deposits. As evidence towards this, is put forward the 

 presence of birds and their remains in the caliche. These birds 

 have, however, apparently been always insignificant in numbers. 

 The same birds exist at the present day, building their nests in 

 crevices in the ground, and they have sometimes been blown up 

 alive in the calicheras. Their guano, although in a few spots on 

 the pampa rather prominent, is in reality little more than a colour, 

 and the amount of nitrate which could be produced from it must be 

 more insignificant than that of the village sewage. The great dis- 

 proof of the guano theoiy, however, is that we find no accumulation 

 of phosphate which would necessarily occur in a corresponding 

 amount to the nitrate, if this idea were true. 



There are other theories also put forward to explain the caliche 

 deposits, which are scarcely worth discussing, among them being 

 one attributing the presence of nitrate vaguely to some volcanic 

 action. The well-known principle in scientific investigations, 

 " Never to invent exceptional theories as long as the ordinary 

 workings of nature are sufficient to explain the facts," should be 

 applied in this case. 



Nitrate exists in small quantities all over the world, in every 

 fertile soil. Vegetation cannot grow without it. How, then, does 

 it originate in these ordinary soils? It originates from the oxidation 

 of the organic materials and ammonia in the soil. This oxidation 

 is brought about by the action of microscopic organisms, called 

 li nitrifying germs." 



Prof. Warington by his experiments has shown that the most 

 favourable conditions, for the active life and work of these nitri- 

 fying organisms, is a porous soil containing plenty of vegetable or 

 animal organic matter, together with sulphate of lime and an alkaline 

 base such as carbonates of potash, soda, or lime. Given a soil of 

 this character, the amount of nitrate produced by the action of these 

 organisms will vary with the temperature ; the rate of manufacture 

 of nitrate being more rapid in a high summer temperature, and 

 diminishing as the weather gets colder. 



