particles; wherefore by the affusion of Water,
Oyl, Tallow, Turpentine, &c. all those reflections are made more faint, and
the beams of light are suffer'd to traject & run through the Paper more
freely.

Hence further we may learn the reason of the whiteness of many bodies, and
by what means they maybe in part made _pellucid_: As white Marble for
instance, for this body is composed of a _pellucid_ body exceedingly
flaw'd, that is, there are abundance of thin, and very fine cracks or
chinks amongst the multitude of particles of the body, that contain in them
small parcels of air, which do so _re-percuss_ and drive back the
penetrating beams, that they cannot enter very deep within that body; which
the _Microscope_ does plainly inform us to be made up of a _Congeries_ of
_pellucid_ particles. And I further found it somewhat more evidently by
some attempts I made towards the making transparent Marble, for by heating
the Stone a little, and baking it in Oyl, Turpentine, Oyl of Turpentine,
&c., I found that I was able to see much deeper into the body of Marble
then before; and one trial, which was not with an unctuous substance,
succeeded better than the rest, of which, when I have a better opportunity,
I shall make further trial.

This also gives us a probable reason of the so much admired _Phaenomena_,
of the _Oculus Mundi_, an _Oval_ stone, which commonly looks like white
Alabaster, but being laid a certain time in Water, it grows _pellucid_, and
transparent, and being suffer'd to lie again dry, it by degrees loses that
transparency, and becomes white as before. For the Stone being of a hollow
spongie nature, has in the first and last of these appearances, all those
pores fill'd with the obtunding and reflecting air; whereas in the second,
all those pores are fill'd with a _medium_ that has much the same
refraction with the particles of the Stone, and therefore those two being
_contiguous_, make, as 'twere, one _continued medium_, of which more is
said in the 15. _Observation_.

There are a multitude of other _Phaenomena_, that are produc'd from this
same Principle, which as it has not been taken notice of by any yet that I
know, so I think, upon more diligent observation, will it not be found the
least considerable. But I have here onely time to hint _Hypotheses_, and
not to prosecute them so fully as I could wish; many of them having a vast
extent in the production of a multitude of _Phaenomena_, which have been by
ot