But
it is in this preliminary step that lies all the difficulty; for, could
we see how every different substance might be dissolved, and every
dissolved substance separated from its solvent at our pleasure, we
should find no difficulty in admitting the cohesion of hard bodies,
whether by means of this doctrine of polished surfaces, or by the
principle of general attraction, a principle which surely comprehends
this particular, termed a cohesive power.
It must not be alleged, that seeing we know not how water dissolves
saline bodies, therefore, this fluid, for any thing that we know, may
also dissolve crystal; and, if water thus dissolves a mineral substance
in a manner unknown to us, it may in like manner deposit it, although
we may not be able to imagine how. This kind of reasoning is only
calculated to keep us in ignorance; at the same time, the reasoning of
philosophers, concerning petrifaction, does not in general appear to be
founded on any principle that is more sound. That water dissolves salt
is a fact. That water dissolves crystal is not a fact; therefore, those
two propositions, with regard to the power of water, are infinitely
removed, and cannot be assimilated in sound physical reasoning.
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