At the present time the collection and export of saltpeter from Chile is a business of great importance. The largest export which has ever taken place in one year was in 1890, when the amount exported was 927,290,430 kilograms; of this quantity 642,506,985 kilograms were sent to England and 86,124,870 kilograms to the United States. Since that time the imports of this salt into the United States have largely increased. According to Pissis[130] these deposits are of very ancient origin. This geologist is of the opinion that the nitrate deposits are the result of the decomposition of feldspathic rocks, the bases thus produced gradually becoming united with the nitric acid provided from the air. According to the theory of Nöllner[131] the deposits are of more modern origin, and due to the decomposition of marine vegetation. Continuous solution of soils beneath the sea gives rise to the formation of great lakes of saturated water, in which occurs the development of much marine vegetation. On the evaporation of this water, due to geologic isolation, the decomposition of nitrogenous organic matter causes generation of nitric acid, which, coming in contact with the calcareous rocks, attacks them, forming calcium nitrate, which, in presence of sodium sulfate, gives rise to a double decomposition into sodium nitrate and calcium sulfate. The fact that iodin is found in greater or less quantity in Chile saltpeter is one of the chief supports of this hypothesis of marine origin, inasmuch as iodin is always found in sea plants, and not in terrestrial plants. Further than this, it must be taken into consideration that these deposits of sodium nitrate contain neither shells nor fossils, nor do they contain any calcium phosphate. The theory, therefore, that they are due to animal origin is scarcely tenable. Lately extensive nitrate deposits have been discovered in the U. S. of Columbia.[132] These deposits have been found extending over thirty square miles and vary in thickness from one to ten feet. The visible supply is estimated at 7,372,800,000 tons, containing from 1.0 to 13.5 percent of nitrate. The deposits consist of a mixture of sodium nitrate, sodium chlorid, calcium sulfate, aluminum sulfate, and insoluble silica. It is thought that the amount of these deposits will almost equal those in Chile and Peru. METHODS OF ANALYSIS.