Dr. William Neicton — Origin of Nitrates in Chili. 341 



In ordinary agricultural soils, unless they are lying fallow, this 

 nitrate is greedily absorbed by the plant almost as fast as it is 

 produced. In fact, except in the case of leguminous crops (clover, 

 beans, peas, etc.), it is almost certain that the plant can only absorb 

 the nitrogeneous food necessary for its growth when it is in the form 

 of nitrate. 



Now, in the enormous plain of Tamarugal we have a porous 

 alluvial soil containing organic matter, chiefly of ancient vegetable 

 origin. The soil contains also sulphate of lime and is basic in its 

 nature, the water percolating through it containing carbonate of soda. 

 The temperature is high, and, in fact, we have all the conditions 

 which Prof. Warington has pointed out as favourable to the rapid 

 conversion of the nitrogen of organic matter into nitrate. On 

 account of the absence of rain in this district, there is now no 

 growing vegetation to absorb the nitrate, and therefore it must 

 accumulate. 



Now let us look at the conformation and situation of the plain of 

 Tamarugal. On one side we have the high Cordilleras running north 

 and south ; then we have this alluvial plain about 30 to 40 miles wide 

 with a very gradual downward slope to the west, where it is again 

 shut in by the coast-line of hills running practically parallel to the 

 Cordilleras. The waters of the western side of the Cordilleras have 

 no escape, except by passing through the soil of the plain. At the 

 western side of the plain the waters are stopped by the coast-line of 

 hills, forming a complete wall from north to south. At the foot of 

 the eastern or landward side of this wall of hills, some thirty miles 

 from the sea, and at the lowest about 2,500 feet above sea-level, 

 these drainage waters of the plain gather aud evaporate, giving up 

 all the salts they have dissolved in their long passage through the 

 soil. The mountain floods which swamp the plain of Tamarugal, at 

 intervals of seven or eight years, are chiefly responsible for the 

 transportation of nitrate from the superficial layers of the pampa 

 soil. It is along the line at the foot of these hills that all the nitrate 

 grounds are situated. Their situation, always on the landward side, 

 is an indication that the caliche is derived from the land, and in 

 itself almost an absolute disproof of the guano or seaweed theories. 

 The occurrence of the nitrate so often up the first slopes of the hills 

 seems at first view strange. But we can see by a simple experiment 

 how this could have happened. If we put some nitrate or salt dis- 

 solved in water in a saucer, and allow it to evaporate, we shall 

 see that immediately it has evaporated, so far as to become a saturated 

 solution, the deposit of crystals of nitrate or salt begins to creep up 

 the side.s of the saucer and even over and down the other side — just 

 as the caliche has crept up the lower slopes of the hills through the 

 porous earthy strata known in Chili as cova and congelo. 



This origin of nitrate is important, amongst other reasons, because 

 one of the great drawbacks to the sale of this material is that 

 many farmers look on it with prejudice, calling it an artificial or 

 chemical manure. It ought to increase its sale, when it is proved 

 to them that, instead of being an artificial manure, it is in reality 



