process now in existence. If we add to the above the prevalent
belief of the time as to the comparative brevity of the period
which had elapsed since the birth of the globe, we can readily
understand the general acceptance of some form of catastrophism
amongst the earlier geologists.

As regards its general sense and substance, the doctrine of
catastrophism held that the history of the earth, since first
it emerged from the primitive chaos, had been one of periods
of repose, alternating with catastrophes and cataclysms of a
more or less violent character. The periods of tranquillity were
supposed to have been long and protracted; and during each of them
it was thought that one of the great geological "formations" was
deposited. In each of these periods, therefore, the condition of
the earth was supposed to be much the same as it is now--sediment
was quietly accumulated at the bottom of the sea, and animals and
plants flourished uninterruptedly in successive generations.
Each period of tranquillity, however, was believed to have been,
sooner or later, put an end to by a sudden and awful convulsion
of nature, ushering in a brief and paroxysmal period, in which
the great physical forces were unchained and permitted to spring
into a portentous activity. The forces of subterranean fire,
with their concomitant phenomena of earthquake and volcano, were
chiefly relied upon as the efficient causes of these periods of
spasm and revolution. Enormous elevations of portions of the
earth's crust were thus believed to be produced, accompanied by
corresponding and equally gigantic depressions of other portions.
In this way new ranges of mountains were produced, and previously
existing ranges levelled with the ground, seas were converted into
dry land, and continents buried beneath the ocean--catastrophe