in. Res. of the United
States for 1918, U. S. Geol. Survey_, pt. 1, 1920, p. 3a.

[11] Spurr, J. E., Who owns the earth?: _Eng. and Min. Jour._, vol. 109,
1920, pp. 389-390.

CHAPTER V

WATER AS A MINERAL RESOURCE

GENERAL GEOLOGIC RELATIONS

With the solid earth as the special care of geology, it may seem
presumptuous for the geologist to claim the waters thereof, but he does
not disclaim this inheritance. Water is so all-pervasive that it is more
or less taken for granted; and so many and so intricate are its
relations that it is not easy to make an objective survey of the water
problem in its relation to geology.

The original source of water, as well as of air, is in molten magmas
coming from below. These carry water and gases,--some of which are
released and some of which are locked up in the rocks on cooling, to be
later released during the alterations of the rocks. It is supposed,
whatever theory of the origin of the earth we favor, that in its early
stages the earth lacked both hydrosphere and atmosphere, and that during
the growth of the earth these gradually accumulated on and near the
surface in the manner stated.

During alterations at the surface water is added to the mineral
constitution of the rocks, and by alterations deep below the surface it
may be subtracted. Water is the agent through which most mineral and
chemical changes of rocks are accomplished. It is the agent also which
is mainly responsible for the segregation of mineral deposits. Water,
both as running water and in the solid form of ice, plays an important
part in determining the configuration of the earth's surface. Water is
the medium in which most sedimentary rocks are formed. It is an
important agent in the development of soil and in organic growth. These
various influences of water on geological processes touch the economic
field at many points, especially in relation to the concentration of
ores and to the development of soils and surface forms.

Water comes even more directly into the field of economic geology as a
mineral resource. Water supplies, for the greatest variety of purposes,
involve geologic considerations at almost every turn.

Finally, water may be an aid or a hindrance to excavation and to a great
variety of structural operations, both in war and in peace; and in this
relation it again affords geologic problems.

The part played by water in geologic processes, such as that of mineral
segregation, is