Simple bodies
have, no doubt, at all periods, obeyed the same laws of attraction, and,
wherever apparent contradictions present themselves, I am confident that
chemistry will in most cases be able to trace the cause to some
corresponding error in the experiment.
Observations made with extreme accuracy over large tracts of land, show that
erupted rocks have not been produced in an irregular and unsystematic
manner. In parts of the globe most remote from one another, we often find
that granite, basalt, and diorite have exercised a regular and uniform
metamorphic action, even in the minutest details, on the strata of
argillaceous slate, dense limestone, and the grains of quartz in sandstones.
As the same endogenous rock manifests almost every where the same degree of
activity, so on the contrary, different rocks belonging to the same class,
whether to the endogenous or the erupted, exhibit great differences in
their character. Intense heat has undoubtedly influenced all these
phenomena, but the degree of fluidity (the more or less perfect mobility of
the particles -- their more viscous composition) has varied very
considerably from the granite to the basalt, while at different geological
p 257
periods (or metamorphic phases of the earth's crust) other substances
dissolved in vapors have issued from the interior of the earth
simultaneously with the eruption of granite, basalt, greenstone porphyry,
and serpentine.
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