otic and psychic elements that sprang forth from it, or
were fostered within its mantles, than can the biography of a human
being be complete with a mere sketch of his physical frame and bodily
growth. The physical and biological evolutions are well recognized as
essential parts of earth history. Although the mental evolutions have
emerged gradually with the biological evolutions, and have run more or
less nearly parallel with them--have, indeed, been a working part of
them--they have been less fully and frankly recognized as elements of
geological history. They have been rather scantily treated in the
literature of the subject; but they are, none the less, a vital part
of the great history. They have found some recognition, though much
too meager, in the more comprehensive and philosophical treatises on
earth-science. It may be safely prophesied that the later and higher
evolutions that grace our planet will be more adequately emphasized as
the science grows into its full maturity and comes into its true place
among the sciences. It is important to emphasize this here, since it
is preeminently the function of a liberal college course to give
precedence to the comprehensive and the essential, both in its
selection of its subject matter and in its treatment of what it
selects. It is the function of a liberal course of study to bring that
which is broad and basal and vital into relief, and to set it over
against that which is limited, special, and technical, however
valuable the latter may be in vocational training and in economic
application.

=Physical and dynamic boundaries of geology--Implications for teaching=

In view of these considerations--and frankly recognizing the
inadequacies of current treatment--let us note, before we go further,
what are the physical and dynamic boundaries of the geologic field,
that we may the better see how that field merges into the domains of
other sciences. This will the better prepare us to realize the nature
of the disciplines for which earth-science forms a suitable basis, as
well as the types of intellectual furniture it yields to the mind.
Obviously these disciplines and this substance of thought should
determine the place of the science in the curriculum of any course
that assumes the task of giving a broad and liberal education.

Earth-science is the domestic chapter of celestial science. Our planet
is but a modest unit among the great celestial assemblage of worlds;
but, mo