Where knowledge can not be
attained from immediate perceptive evidence, we may be allowed from
induction, no less than from a careful comparison of facts, to hazard a
conjecture by which granite would be restored
p 286
to a portion of its contested right and title to be considered as a
'primordial' rock.
The recent progress of geognosy, that is to say, the more extended knowledge
of the geognostic epochs characterized by differences of mineral formations,
by the peculiarities and succession of the organisms contained within them,
and by the position of the strata, whether uplifted or inclined
horizontally, leads us, by means of the causal connection existing among all
natural phenomena, to the distribution of solids and fluids into the
continents and seas which constitute the upper crust of our planet. We here
touch upon a point of contact between geological and geographical geognosy
which would constitute the complete history of the form and extent of
continents. The limitation of the solid by the fluid parts of the earth's
surface and their mutual relations of area, have varied very considerably in
the long series of geognostic epochs. They were very different, for
instance, when carboniferous strata were horizontally deposited on the
inclined beds of the mountain limestone and old red sandstone; when lias and
oolite lay on a substratum of keuper and muschelkalk, and the chalk rested
on the slopes of green sandstone and Jura limestone.
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