r tropical countries, and the changes there are most rapid, so that
the production of saltpetre, favored by moisture and hot winds, attains
its highest limit in parts of India and the bordering countries.

During the prevalence of dry winds, the earth in many districts of India
becomes frosted over with nitrous efflorescences, and the great quantity
shipped from the commercial ports, and that consumed in China, is thus a
natural production of that region. The increased amount due to tropical
influences will be seen in the instances here given of the produce from
the rich earths of different countries:--

_Natural_.

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 sal