y with organic matter. Deposits of this
type are known in many places, the most important being those of Sicily
and of the Gulf Coast in the United States. In the latter region beds of
limestone carry lenses of sulphur and gypsum which are apparently
localized in dome-like upbowings of the strata. The deposits are
overlain by several hundred feet of loose, water-bearing sands, through
which it is difficult to sink a shaft. An ingenious and efficient
process of mining is used whereby superheated water is pumped down to
melt the sulphur, which is then forced to the surface by compressed air
and allowed to consolidate in large bins. The Sicilian deposits are
similar lenses in clayey limestones containing 20 to 25 per cent of
sulphur, associated with gypsum and bituminous marl; they are mined by
shafts.

Concerning the origin of these deposits several theories have been
advanced. It has been thought that the materials for the deposits were
precipitated at the same time as the enclosing sediments; and that the
sulphur may have been formed by the oxidation of hydrogen sulphide in
the precipitating waters through the agency of air or of
sulphur-secreting bacteria, or that it may have been produced by the
reduction of gypsum by organic matter or bacteria. Others have suggested
that hot waters rising from igneous rocks may have brought in both the
sulphur and the gypsum, which in crystallizing caused the upbowing of
the strata which is seen in the Gulf fields (see also p. 298).

Native sulphur is also found in mineral springs from which hydrogen
sulphide issues, where it is produced by the oxidation of the hydrogen
sulphide. It likewise occurs in fissures of lava and around volcanic
vents, where it has probably been formed by reactions between the
volcanic gases and the air. The Japanese and Chilean deposits are of the
volcanic type.

POTASH

ECONOMIC FEATURES

Potash is used principally as a component of fertilizers in agriculture.
It is also used in the manufacture of soap, certain kinds of glass,
matches, certain explosives, and chemical reagents.

For a long time potash production was essentially a German monopoly. The
principal deposits are in the vicinity of Stassfurt in north central
Germany (about the Harz Mountains). Stassfurt salts are undoubtedly
ample to supply the world's needs of potash for an indefinite future.
However, other deposits, discovered in the Rhine Valley in Alsace in
1904, have been proved