And I know not, _Pyrophilus_,
whether I might not add, that even the Motion of the Small Parts of a
Visible Object may in some cases contribute, though it be not so easie to
say how, to the Producing or the Varying of a Colour; for I have several
times made a Liquor, which when it has well settled in a close Vial, is
Transparent and Colourless, but as soon as the Glass is unstopp'd, begins
to fly away very plentifully in a White and Opacous fume; and there are
other Bodies, whose Fumes, when they fill a Receiver, would make one
suspect it contains Milk, and yet when these Fumes settle into a Liquor,
that Liquor is not White, but Transparent; And such White Fumes I have seen
afforded by unstopping a Liquor I know, which yet is it self Diaphanous and
Red; Nor are these the only Instances of this Kind, that our Tryals can
supply us with. And if the Superficial Corpuscles be of the Grosser sort,
and be so Framed, that their differing Sides or Faces may exhibit differing
Colours, then the Motion or Rest of those Corpuscles may be considerable,
as to the Colour of the Superficies they compose, upon this account, that
sometimes more, sometimes fewer of the Sides dispos'd to exhibit such a
Colour may by this means become or continue more Obverted to the Eye than
the rest, and compose a Physical Surface, that will be more or less
sensibly interrupted; As, to explane my meaning, by proposing a gross
Example, I remember, that in some sorts of Leavy Plants thick set by one
another, the two sides of whose Leaves were of somewhat differing Colours,
there would be a notable Disparity as to Colour, if you look'd upon them
both when the Leaves being at Rest had their upper and commonly expos'd
sides Obverted to the Eye, and when a breath of Wind passing thorow them,
made great Numbers of the usually Hidden sides of the Leaves become
conspicuous.
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