of
economic geologist implies no mastery of the entire field. There is yet
no crowding.

TREATMENT OF THE SUBJECT IN THIS VOLUME

In scope and manner of treatment this volume follows somewhat the
writer's presentation of the subject in university teaching. The purpose
is to explain the nature of the economic demands for the science of
geology, and to discuss something of the philosophy of the finding and
use of raw materials.

Somewhat generalized statistics are used as a means of gaining
perspective. No effort has been made for detailed accuracy or for
completeness. So far as possible the quantitative features are expressed
in general proportions, and where specific figures are given they are
meant to indicate only such general proportions. The thought has been
not to be so specific that the figures would soon be out of date. All
standard statistical sources have been drawn on, but the principal
sources have been the results of the various special investigations
called out by the war, in which the writer had a part.

On the geologic side many sources have been drawn on outside of the
writer's own experience. For the most part, no specific references or
acknowledgments are made, on the ground that the book aims to present
the general features which are now the more or less common knowledge of
economic geologists. To make the references really adequate for
exhaustive study would not only burden the text, but would require a
specificity of treatment which it has been hoped to avoid.

The illustrative cases chosen for discussion are often taken from the
writer's field of experience. This field has been principally the Lake
Superior region, but has included also the principal mineral deposits of
North America, Cuba, and limited areas in South America and Europe. Thus
the Lake Superior iron and copper region might seem to be brought
forward more than is warranted by its scientific or economic importance.
For this, the writer offers no apology. An author's perspective is
largely determined by his background of training and experience, and a
frank recognition of this fact may aid in determining the weight to be
given to his conclusions. It might even add to scientific efficiency if
each writer were to confine his discussion almost solely to matters
within his own range of observation and study.

The writer's indebtedness for information derived from the printed page
and for personal discussion and advice is of wide r