ent, yet by its power of Reflecting some
Incident Rays of Light, is in some measure a Natural _Speculum_, being long
agitated with a Whisk or Spoon, loses its Transparency, and becomes very
White, by being turn'd into Froth, that is into an Aggregate of Numerous
small Bubbles, whose Convex Superficies fits them to Reflect the Light
every way Outwards. And 'tis worth Noting, that when Water, for instance,
is Agitated into Froth, if the Bubbles be Great and Few, the Whiteness will
be but Faint, because the number of _Specula_ within a Narrow compass is
but Small, and they are not Thick set enough to Reflect so Many Little
Images or Beams of the Lucid Body, as are requisite to produce a Vigorous
sensation of Whiteness: And partly least it should be said, that the
Whiteness of such Globulous Particles proceeds from the Air Included in the
Froth; (which to make good, it should be prov'd that the Air it self is
White) and partly to illustrate the better the Notion we have propos'd of
Whiteness, I shall add, that I purposely made this Experiment, I took a
quantity Fair water, & put to it in a clear Glass phial, a convenient
quantity of Oyl or Spirit of Turpentine, because that Liquor will not
incorporate with Water, and yet is almost as Clear and Colourless as it;
these being Gently Shaken together, the Agitation breaks the Oyl (which as
I said, is Indispos'd to Mix like Wine or Milk _per minima_ with the Water)
into a Multitude of Little Globes, which each of them Reflecting Outwards a
Lucid Image, make the Imperfect Mixture of the two Liquors appear Whitish;
but if by Vehemently Shaking the Glass for a competent time you make a
further Comminution of the Oyl into far more Numerous and Smaller
_Globuli_, and thereby confound it also better with the Water, the Mixture
will appear of a Much greater Whiteness, and almost like Milk; whereas if
the Glass be a while let alone, the Colour will by degrees Impair, as the
Oyly globes grow Fewer and Bigger, and at length will quite Vanish, leaving
both the Liquors Distinct and Diaphanous as before. And such a Tryal hath
not ill succeeded, when insteed of the Colourless Oyl of Turpentine I took
a Yellow Mixture made of a good Proportion of Crude Turpentine dissolv'd in
that Liquor; and (if I mis-remember not) it also Succeeded better than one
would expect, when I employ'd an Oyl brought by Filings of Copper infused
in it, to a deep Green. And this (by the way) may be the Reason, why often
t