ce given by
authority clings as a hindrance to progress. He had formed no distinct
idea of what he meant by an Earthquake, and so confusedly mixes up all
elevations or depressions of a permanent character with "subversions,
conversions and transpositions of parts of the earth," however sudden or
transitory, under the name of Earthquakes.

A like confusion is far from uncommon amongst geological writers, even
at the present day, and examples might be quoted from very late writings
of even some of the great leaders of English Geology.

From the seventeenth to the middle of the eighteenth century one finds
floods of hypotheses from Flamsteed, Hoettinger, Amontons, Stukeley,
Beccaria, Percival, Priestly, and a crowd of others, in which
electricity, then attracting so much attention, is often called upon to
supply causation for a something of which no clear idea had been formed.
Count Bylandt's singular work, published in 1835, though showing a
curious _partial_ insight in point of advancement, might be put back
into that preceding period.

In 1760 appeared the very remarkable Paper, in the fifty-first volume of
the "Philosophical Transactions," of the Rev. John Mitchell, of
Cambridge, in which he views an Earthquake as a sudden lifting up, by a
rapid evolution of steam or gas beneath, of a portion of the earth's
crust, and the lateral transfer of this gaseous bubble beneath the
earth's crust, bent to follow its shape and motion, or that of a wave of
liquid rock beneath, like a carpet shaken on air. Great as are certain
collateral merits of Mitchell's Paper, showing observation of various
sorts much in advance of his time, this notion of an Earthquake is such
as, had he applied to it even the imperfect knowledge of mechanics and
physics then possessed in a definite manner, he could scarcely have
failed to see its untenable nature. That the same notion, and in a far
more extravagant form, should have been reproduced in 1843 by Messrs.
Rogers, by whom the gigantic parallel anticlinals, flanks and valleys of
the whole Appalachian chain of mountains are taken for nothing more than
the indurated foldings and wrinkles of Mitchell's carpet, is one of the
most salient examples of the abuse of hypothesis untested by exact
science.

Neither Humboldt nor Darwin, great as were the opportunities of
observation enjoyed by both, can be supposed to have formed any definite
idea of _what_ an Earthquake is; and the latter, who had observe