in normal times are Germany and Great
Britain. France and Belgium were both large producers and exporters
before the war, but the war greatly reduced their capacity to produce
for the time being. Sweden, Denmark, Austria, Japan, and Switzerland all
produce less extensively but have considerable surplus available for
export. Italy and Spain have large productions, which are about
sufficient for their own requirements. Holland and Russia import large
amounts from the other European countries. The far eastern trade absorbs
the excess production of Japan. In South Africa and Australasia,
production nearly equals demand. In Canada, although the industry has
been growing very rapidly, the demand still exceeds production. In South
and Central America, Mexico and the West Indies, the demand is
considerable and will probably increase; production has thus far been
insufficient. Several modern mills are either recently completed or
under construction in these countries, and concessions have been granted
for several others. These new mills are largely financed by American
capital.

The United States is the largest single producer of cement in the world,
its annual production being about 45 per cent of the world's total.
Domestic consumption has always been nearly as great as the production,
and exports have usually not exceeded 4 per cent of the total shipments
from the mills. South and Central America offer fields for exportation
of cement from the United States.

GEOLOGIC FEATURES OF THE COMMON ROCKS

To describe the geologic features of the common rocks used in commerce
would require a full treatise on the subject of geology. These are the
bulk materials of the earth and in them we read the geologic history of
the earth. In preceding chapters a brief outline has been given of the
relative abundance of the common earth materials and of the processes
producing them. In comparison, the metalliferous deposits are the merest
incidents in the development of this great group of mineral resources.

In this section reference will be made only to a few of the rock
qualities and other geologic features which require first attention in
determining the availability of a common rock for commercial use. The
list is very fragmentary, for the reason that the uses are so many and
so varied that to describe all the geologic features which are important
from the standpoint of all uses would very soon bring the discussion far
beyond the confin