It should not be forgotten, however, that from one point of view
there is a truth in catastrophism which is sometimes overlooked
by the advocates of continuity and uniformity. Catastrophism
has, as its essential feature, the proposition that the known
and existing forces of the earth at one time acted with much
greater intensity and violence than they do at present, and they
carry down the period of this excessive action to the commencement
of the present terrestrial order. The Uniformitarians, in effect,
deny this proposition, at any rate as regards any period of the
earth's history of which we have actual cognisance. If, however,
the "nebular hypothesis" of the origin of the universe be well
founded--as is generally admitted--then, beyond question, the
earth is a gradually cooling body, which has at one time been
very much hotter than it is at present. There has been a time,
therefore, in which the igneous forces of the earth, to which we
owe the phenomena of earthquakes and volcanoes, must have been
far more intensely active than we can conceive of from anything
that we can see at the present day. By the same hypothesis, the
sun is a cooling body, and must at one time have possessed a
much higher temperature than it has at present. But increased
heat of the sun would seriously alter the existing conditions
affecting the evaporation and precipitation of moisture on our
earth; and hence the aqueous forces may also have acted at one
time more powerfully than they do now.
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