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Here is a supposition of our author that corresponds to nothing which
has yet been observed any where else, so far as I know. It is concerning
a mineral vein, one which does not appear to differ in any respect from
other mineral veins, except in being worked in that open manner which
has given our author an idea of its being a valley. He then supposes
that valley (or rather empty vein) to have been in this mountain when at
the bottom of the sea, and that this mineral vein had then been filled
with those materials which now are found in that space between the two
sides of the separated rock. This is a very different operation from
that of infiltration, which is commonly supposed to be the method of
filling mineral veins; but, we shall soon see the reason why our author
has here deserted the common hypothesis, and has adopted another to
serve the occasion, without appearing to have considered how perfectly
inconsistent those two suppositions are to each other. That mineral
veins have been filled with matter in a fluid state, is acknowledged by
every body who has either looked at a mineral vein in the earth, or in a
cabinet specimen; mineralists and geologists, in general, suppose this
to have been done by means of solutions and concretions, a supposition
by no means warranted by appearances, which, on the contrary, in general
demonstrate that the materials of those veins had been introduced in the
fluid state of fusion.
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