lating these subterranean forces to
ordinary earthquake-forces; but modern inquiries have shown that,
besides elevations of surface, subsidences are thus produced; that local
upheavals, as well as the general upheavals which raise continents, come
within the same category; and that all these changes are probably
consequent on the progressive collapse of the Earth's crust upon its
cooling and contracting nucleus. In the third place, we find that beyond
these two great antagonistic agencies, modern Geology recognizes sundry
minor ones: those of glaciers and icebergs, those of coral-polypes;
those of _Protozoa_ having siliceous or calcareous shells--each of which
agencies, insignificant as it seems, is found capable of slowly working
terrestrial changes of considerable magnitude. Thus, then, the recent
progress of Geology has been a still further departure from primitive
conceptions. Instead of one catastrophic cause, once in universal
action, as supposed by Werner--instead of one general continuous cause,
antagonized at long intervals by a catastrophic cause, as taught by
Hutton; we now recognize several causes, all more or less general and
continuous. We no longer resort to hypothetical agencies to explain the
phenomena displayed by the Earth's crust; but we are day by day more
clearly perceiving that these phenomena have arisen from forces like
those now at work, which have acted in all varieties of combination,
through immeasurable periods of time.

* * * * *

Having thus briefly traced the evolution of geologic science, and noted
its present form, let us go on to observe the way in which it is still
swayed by the crude hypotheses it set out with; so that even now,
doctrines long since abandoned as untenable in theory, continue in
practice to mould the ideas of geologists, and to foster sundry beliefs
that are logically indefensible. We shall see, both how those simple
sweeping conceptions with which the science commenced, are those which
every student is apt at first to seize hold of, and how several
influences conspire to maintain the twist thus resulting--how the
original nomenclature of periods and formations necessarily keeps alive
the original implications; and how the need for arranging new data in
some order, results in their being thrust into the old classification,
unless their incongruity with it is very glaring. A few facts will best
prepare the way for criticism.

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