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BIGSBY MISSING SEDIMENTARY FORMATIONS.
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VOL. XX. PART I.
by steps. The general idea of any advance
arrives first, and may perhaps lie dormant
for years, when follows its development by
another workman, and perhaps in another
country

just as Vicomte d'Archiac, in
1848, sketched in unmistakeable language
the principal features of the great Terripetal
Theory, which Bronn, in 1862, made his
own by the most masterly elaboration,
— Ami Boue, in 1852, having prepared the
way by an elaborate article in the ' Bul-
letin de la Societe Geologique de France,'
2nd series, vol. ix. p. 437. While in their
vertical order of succession the sedimentary
rocks never vary, unless disturbed, they differ
greatly in thickness and extent — far stretch-
ing out and thin in plains, thick and limited
in area among mountains, as we see
abundantly verified in the Americas, India,
Russia, &c. But they have also been from
the very earliest periods largely, and fre-
quently, absent from their normal situa-
tions, and much more so than appears in
systematic works; and it is easy to see,
from the vast and universal prevalence of
these suspensions and removals of deposits,
that it will be one day proved that the
emerged tracts were at all periods so ex-
tensive and so united as to constitute from
one-fifth to one-third of the whole surface
of the globe.
While any given district was in a state of
emergence, various sediments were being
deposited in the neighbouring sea, which
was at the same time tenanted by a fauna
so balanced and harmonized that the indi-
viduals could thrive and follow the prompt-
ings of their instincts — whole races dying
out, we may safely suppose. Now, if only
one such epoch commence, become mature,
and decline, we see that the raised land must
have remained as such for an immensely
long period. What then must have been
the length of that period of time during
which an emerged tract remained through
ten or twenty epochs above water, as has
frequently occurred?* Missing formations,
then, hold a high and important place as a
result of one of the constructive processes of

Canada, Hudson's Bay, Germany, &c. &c.