392 EEPORT OF NATIONAL MUSEUM, 1899. 



It is also found in certain soils of tropical countries, as noted under 

 origin. In the United States it has been found in caves of the South- 

 ern States, as those of Madison County, Kentucky, but never in 

 commercial qualities. The chief commercial source of the salt has 

 been the artificial nitrates of France, Germany, Sweden, and other 

 European countries. It is also prepared artificially from soda niter. 



2. Soda Niter. 



Nitrate of sodium, NaNOj. This in its pure state is a white or 

 colorless salt, but in nature brown or bright lemon yellow (See Speci- 

 mens in jar. No. 67278, U.S.N.M.), of a slight saline taste, but with a 

 peculiar cooling sensation when placed upon the tongue. It is by 

 far the most common of the nitrates, and indeed the only one of the 

 natural salts of any great commercial value, owing to the comparative 

 rarity of the others. Though found to a slight extent in caves and 

 protected places, the commercial supply is drawn almost wholly from 

 the desert regions of the Pacific coast of South America and particu- 

 larly from Chile, the chief deposits being found in the provinces of 

 Tarapaca and Antofagasta, 



According to the elournal of the Society of Chemical Industry: ^ 



The total area of the province of Tarapaca is 16, 789 J square miles, and it is divided 

 naturally into five distinct and well-defined zones. The first of these zones com- 

 mences on the shores of the Pacific and has an average width, west to east, of 18 miles. 

 It is formed, in the first place, of the beach; and, in the second, of the coast range, 

 which attains an altitude varying from 1,125 to 5,800 feet above the sea level. This 

 zone may be denominated the guano and mining zone. * * * This belt as it 

 advances eastward becomes more and more depressed and terminates in a series of 

 pampas (open plains) , having an elevation of 3,500 to 3,800 feet above the sea level. 

 Nearly all these pampas contain vast beds of salts, sulphate of soda, and sulphate of 

 Ume. They are known locally by the name of " salares." In some parts of the desert 

 of Atacama the beds of nitrate of soda are found under these salares deposits, but 

 in Tarapaca the caliche (nitrate earth) is found only under a bed of conglomerate 

 known as "costra." * * * 



The second zone — the nitrate zone — commences on the edge of the Camarones 

 Gully and extends southward to the desert of Atacama. Up to 1858 it was believed 

 that the nitrate beds did not extend southward beyond the Loa Gully, but in that 

 year beds were discovered in what was then the Bolivian littoral. Exjilorations 

 which were effected in 1872 proved that the nitrate beds extended northward beyond 

 the Camarones Gully and that they reached as far as the Chaca Gully and even as far 

 as the Azapa Valley, in the province of Alrica. * * * The quantity and quality of 

 the caliche varies very considerably in different parts of the zone, but the dimensions 

 of the nitrate area may be set down at 120 geographical miles in length north to south, 

 and 2 geographical miles in width east to west. It is estimated that the beds contain 

 the enormous quantity of 1,980,630,502 quintals of niter, and it is stated that with the 

 present export duty which is equal to 27 pence per quintal, the deposits will yield a 

 revenue of £230,809,474. 



1 Volume VI, 1887, pp. 228, 229. 



