THE NORTHERN DESERT OF CHILE, which extends as far south as latitude 30°, is the scene of considerable economic activity. Great deposits of nitrate of soda lie in a narrow strip of land, running from north to south for about 500 miles, at a distance from the coast varying from fifteen miles in the north to ninety in the south. The origin of these deposits has not yet been finally determined, but they appear to be due to the chemical combination of nitric acid, derived from great quantities of decaying seaweed in a basin frequently refilled by the tide, with the sodium salts which remained after the evaporation of the water from the basin. The aridity of the climate has been the all-important factor in the preservation of the nitrate, as even a moderate rainfall would have led to its destruction. The exports of nitrate of soda, mainly for use as a fertiliser, but also for the manu facture of nitric acid and other substances, have increased very largely within recent years, and for a time it seemed that the end of the Chilean industry was in sight. Lately, however, large de posits have been found in Antofagasta and Atacama, and it is now believed that the resources of the country are sufficient to meet the demands upon it for a considerable time to come. The chief purchasers of Chilean nitrate are Germany, which uses it largely in the cultivation of beet, Britain, the United States, and France ; and it is exported to these countries mainly through the ports of Iquique, Caleta Buena, Tocopilla, Antofagasta, and Taltal. Formerly the trade was almost entirely in British hands, but Germany has now acquired a considerable share in it. The total
export of nitrate in 1910 amounted to over 5,000,000 tons.
The metalliferous deposits of the country are chiefly found in this arid northern region, and in the less arid one immediately to the south, which lies between the thirtieth and thirty-third parallels, and may be called the SEMI-DESERT REGION. Gold, silver, and copper exist, as in several other parts of the world, more especially where rocks of volcanic or plutonic origin come into contact with metamorphosed sedimentary strata. In the coast range, gold and silver are obtained ; while further inland there are many silver veins, which it does not pay to work, as that metal is not associated with copper. Still further east, in the main range of the Andes, there are numerous veins of silver and copper, which are worked mainly on account of the latter metal. Copper is, after nitrate, the most valuable export of Chile. The average output (1909-11) is about 38,000 tons, or a little over 4 per cent. of the world's production.
Agriculture is all but impossible in the Northern Desert, but in the Semi-desert Region it is carried on to a considerable extent in those districts in which the land can be made productive by irrigation. The provinces of Coquimbo and Aconcagua are able to supply their own needs, and even to export a certain amount to the north, where everything required by the great mining population has to be imported. Until recently, even water had to be brought by ship, but now most of the mining towns are supplied from the Andes.