these
universal strata had been in succession precipitated from a chaotic
menstruum which once covered our planet. Thus, on a very incomplete
acquaintance with a thousandth part of the Earth's crust, he based a
sweeping generalization applying to the whole of it. This Neptunist
hypothesis, mark, borne out though it seemed to be by the most
conspicuous surrounding facts, was quite untenable if analyzed. That a
universal chaotic menstruum should deposit a series of numerous
sharply-defined strata, differing from one another in composition, is
incomprehensible. That the strata so deposited should contain the
remains of plants and animals, which could not have lived under the
supposed conditions, is still more incomprehensible. Physically absurd,
however, as was this hypothesis, it recognized, though under a distorted
form, one of the great agencies of geological change--the action of
water. It served also to express the fact, that the formations of the
Earth's crust stand in some kind of order. Further, it did a little
towards supplying a nomenclature, without which much progress was
impossible. Lastly, it furnished a standard with which successions of
strata in various regions could be compared, the differences noted, and
the actual sections tabulated. It was the first provisional
generalization; and was useful, if not indispensable, as a step to truer
ones.

Following this rude conception, which ascribed geological phenomena to
one agency, acting during one primeval epoch, there came a
greatly-improved conception, which ascribed them to two agencies, acting
alternately during successive epochs. Hutton, perceiving that
sedimentary deposits were still being formed at the bottom of the sea
from the detritus carried down by rivers; perceiving, further, that the
strata of which the visible surface chiefly consists, bore marks of
having been similarly formed out of pre-existing land; and inferring
that these strata could have become land only by upheaval after their
deposit; concluded that throughout an indefinite past, there had been
periodic convulsions, by which continents were raised, with intervening
eras of repose, during which such continents were worn down and
transformed into new marine strata, fated to be in their turns elevated
above the surface of the ocean. And finding that igneous action, to
which sundry earlier geologists had ascribed basaltic rocks, was in
countless places a cause of disturbance, he taught tha