n of the Acid Spirit seems in both cases,
but to weaken the Colour of the Liquor on which it falls. And so though it
destroy Redness in the Tincture of Brazil, as well as produce Red in the
Tincture of _Chochineel_, its Operations may be Uniform enough, since as
Crimson seems to be little else than a very deep Red, with (perhaps) an Eye
of Blew, so some kinds of Red seem (as I have lately noted) to be little
else than heightned Yellow. And consequently in such Bodies, the Yellow
seems to be but a diluted Red. And accordingly Alcalizate Solutions and
Urinous Spirits, which seem dispos'd to Deepen the Colours of the Juices
and Liquors of most Vegetables, will not only restore the Solution of
_Cochineel_ and the Infusion of Brazil to the Crimson, whence the Spirit of
Salt had chang'd them into a truer Red; but will also (as I lately told
you) not only heighthen the Yellow Juice of Madder into Red, but advance
the Red Infusion of Brazil to a Crimson. But I know not whether it will not
be much safer to derive these Changes from vary'd Textures, than certain
kinds of Bodies; and you will perhaps think it worth while, that I should
add on this occasion, That it may deserve some Speculation, why,
notwithstanding what we have been observing, though Blew and Purple seem to
be deeper Colours than Red, and therefore the Juices of Plants of either of
the two former Colours may (congruously enough to what has been just now
noted) be turn'd Red by Spirit of Salt or _Aqua-fortis_, yet Blew Syrrup of
Violets and some Purples should both by Oyl of Tartar and Spirit of Urine
be chang'd into Green, which seems to be not a deeper but a more diluted
Colour than Blew, if not also than Purple.

_EXPERIMENT XXXVIII._

It would much contribute to the History of Colours, if _Chymists_ would in
their Laboratories take a heedfull notice, and give us a faithfull account
of the Colours observ'd in the Steams of Bodies either Sublim'd or
Distill'd, and of the Colours of those Productions of the Fire, that are
made up by the Coalition of those Steams. As (for Instance) we observe in
the Distilling of pure Salt peter, that at a certain season of the
Operation, the Body, though it seem either Crystalline, or White, affords
very Red Fumes: whereas though Vitriol be Green or Blew, the Spirit of it
is observ'd to come over in Whitish Fumes. The like Colour I have taken
notice of in the Fumes of several other Concretes of differing Colours, and
Natures, espe