In which Experiment, there are three Observables that seem very manifestly
to prove the porousness of these seemingly close bodies: the first is their
acquiring a transparency, and losing their whiteness after steeping in
water, which will seem the more strongly to argue it, if what I have
already said about the making transparent, or clarifying of some bodies, as
the white powder of beaten Glass, and the froth of some glutinous
transparent liquor be well consider'd; for thereby it will seem rational to
think that this transparency arises from the insinuation of the water
(which has much the same refraction with such stony particles, as may be
discover'd by Sand view'd with a _Microscope_) into those pores which were
formerly repleat with air (that has a very differing refraction, and
consequently is very reflective) which seems to be confirm'd by the second
Observable, namely, the increase of weight after keeping, and decrease upon
drying. And thirdly, seem'd yet more sensibly confirm'd by the multitude of
bubbles in the last Experiment.
We find also most Acid Salts very readily to dissolve and separate the
parts of this body one from another; which is yet a further Argument to
confirm the porousness of bodies, and will serve as such, to shew that even
Glass also has an abundance of pores in it, since there are several
liquors, that with long staying in a Glass, will so _Corrode_ and eat into
it, as at last, to make it pervious to the liquor it contain'd, of which I
have seen very many Instances.
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