France, Church of Mousseau, 5-3/8 per cent.
    " Cavern of Fouquieres, 3-1/2 "
  U. States, Tennessee, dirt of caves, 0.86 "
  Ceylon, Cave of Memoora, 3-1/10 "
  Upper Bengal, Tirhoot, earth simply, 1-6/10 "
  Patree in Guzerat, best sweepings, 8-7/10 "

In each case the salt is mixed saltpetres.

Artificial.

  France, 100 lbs. earth from
       plantations afford 8 to 9 oz. 
  Hungary and Sweden, from
       the same, 1/2 to 2-3/10 per cent.

It may be calculated that the flesh of animals, free from bone, carefully decomposed, will afford ninety-five pounds of saltpetre for one thousand pounds thus consumed.

In the manufacture of saltpetre, the earths, whether naturally or artificially impregnated, are mixed with the ashes from burnt wood, or salts of potash, so that this base may take the place of all others, and produce long prisms of potash saltpetre.

In this country there are numerous caves of great extent in Kentucky, Tennessee, and Missouri, from which saltpetre has been manufactured.  Under the most favorable conditions of abundance of labor, obtainable at a low price, potash saltpetre can be made at a cost about one-fourth greater than the average price of India saltpetre, and those sources of supply are the best natural deposits known on this side of the Rocky Mountains.  Where there is an insufficient supply of manure in a country, resort to the artificial production of saltpetre is simply a robbery committed on the resources of the agriculturists, and it is only during the pressure of a great struggle like that of the wars of Napoleon, that the conversion into saltpetre of materials which can become food for the community would be permitted.

Hitherto, in peaceful times, our supply of saltpetre has come from India through commercial channels; but twice within a few years this course of trade has been interrupted by the British Government, and the price of a necessary article has been greatly enhanced,—­leading reflecting minds to the inquiry after other sources whence to draw the quantity required for an increasing consumption.  On the boundary between Peru and Chili, in South Peru, about forty miles from the ports of Conception and Iquique, is a depression in the general surface of a saline desert, where a bed of soda saltpetre, about two and a half feet thick and one hundred and fifty miles long, exists.  The salt is massive, and, occurring in a rainless climate, it is dry, and contains about sixty per cent. of pure soda saltpetre.  In Brazil, on the San Francisco, the same salt is found extending sixty or seventy miles,—­and again near the town of Pilao Arcado, the beds being about two hundred and forty miles from Bahia, but at present inaccessible for want of roads.  The Peruvian native saltpetre is rudely refined in the desert, and then transported