Page:Popular Science Monthly Volume 11.djvu/359

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Chemical art has not done anything toward the appropriation of this obstinate element. Nothing nitrogenous can be made of nitrogen. The manufacturers depend on gatherings from the sparingly distributed nitrates of the earth. As machinists have dreamed of perpetual motion, sleeping chemists may dream of an invention to bring atmospheric nitrogen into use, that all the barren places may be made fertile, and the whole earth flourish as a garden of fatness. But for this dream to realize the proportions of a fair probability it is quite essential that chemistry should be well asleep.

The chief commodities bearing nitrogen are nitre or saltpetre (potassium or sodium nitrate), and ammonia. In Hindostan, the rich soil-mould, warm and alkaline, becomes thinly crusted with nitrate, which is gathered and brought to market as East India nitre. Gunpowder, gun-cotton, and nitro-glycerine, as well as chemical products, are made with it. In the War of 1812, America was thrown upon her own sources for gunpowder-material, and enough nitre was found in the cave-deposits of the Southwestern States. Then France was hemmed in by hostile armies, and had neither nitre nor cave-deposits, but it was after the work of "Lavoisier of immortal memory," and the government put trust in chemistry. Berthollet and the rest soon justified the trust in the perfection of the "nitre-plantations"—beds of farm-refuse with wood-ashes exposed to the air.

These products, soil-nitre and compost-nitre, and the ammonia obtained as a by-product in the manufacture of illuminating gas, serve their several purposes in the arts and applications of man, but their limited quantities do not warrant their addition to the soil for the increased growth of food. Now, unlike these common supplies, the earth possesses a special resource for nitrogen in combination, anomalous in being fully mineralized and remarkable in being both concentrated and extensive, a chain of mines full of nitre. On the Pacific coast of South America, extending from the fourth to the fortieth degree of south latitude, about 2,400 miles along the slope of the Andes to the sea, in Bolivia, Peru, and part of Chili, there has been found a line of deposits of sodium nitrate, the "Peruvian nitre." The beds are of variable thickness, covered by one to ten yards' depth of earth and half-formed sandstone. The dry soil of the most of this rainless country is pervaded, in some degree, with this deposit. The mummied remains of the old Peruvian people are embalmed with it by the earth in which they were buried; and its crystals glisten on those ghastly relicts which were presented in the Peruvian department of the Centennial Exhibition, and those brought to this country by Dr. Steere. It has been estimated that in the province of Tarapaca, within fifty square leagues, the quantity of the nitre is not less than 63,000,000 tons. The appropriation of this vast resource has been taken up rather slowly, but has much increased for ten or twelve years past. Vessels laden with it go to the coasts of manu-