on proportionably mingl'd
with this other Blew Liquor did not make a Blew mixture, but, as I
expected, a fair Green, upon the account of the Urinous Salt that was in
the _Menstruum_.

_EXPERIMENT XIX._

To shew the _Chymists_, that Colours may be made to Appear or Vanish, where
there intervenes no Accession or Change either of the Sulphureous, or the
Saline, or the Mercurial principle (as they speak) of Bodies: I shall not
make use of the Iris afforded by the Glass-prism, nor of the Colours to be
seen in a fair Morning in those drops of Dew that do in a convenient manner
Reflect and Refract the Beams of Light to the Eye; But I will rather mind
them of what they may observe in their own Laboratories, namely, that
divers, if not all, Chymical Essential Oyls, as also good Spirit of Wine,
being shaken till they have good store of Bubbles, those Bubbles will (if
attentively consider'd) appear adorn'd with various and lovely Colours,
which all immediately Vanish, upon the relapsing of the Liquor that affords
those Bubbles their Skins, into the rest of the Oyl, or Spirit of Wine, so
that a Colourless Liquor may be made in a trice to exhibit variety of
Colours, and may lose them in a moment without the Accession or Diminution
of any of its Hypostatical Principles. And, by the way, 'tis not unworthy
our notice, that some Bodies, as well Colourless, as Colour'd, by being
brought to a great Thinness of parts, acquire Colours though they had none
before, or Colours differing from them they were before endued with: For,
not to insist on the Variety of Colours, that Water, made somewhat
Glutinous by Sope, acquires, when 'tis blown into such Sphaerical Bubbles as
Boys are wont to make and play with; Turpentine (though it have a Colour
deep enough of its own) may (by being blown into after a certain manner) be
brought to afford Bubbles adorn'd with variety of Orient Colours, which
though they Vanish after some while upon the breaking of the Bubbles, yet
they would in likelihood always exhibit Colours upon their _Superfices_,
(though not always the same in the same Parts of them, but Vary'd according
to the Incidence of the Sight, and the Position of the Eye) if their
Texture were durable enough: For I have seen one that was Skill'd at
fashioning Glasses by the help of a Lamp, blowing some of them so strongly
as to burst them, whereupon it was found, that the Tenacity of the Metall
was such, that before it broke it suffer'd it self to b