he Tinging parts of the Roses, as a production of Redness;
and lastly, if you be destitute of Spirit of Urine, you may change the
Colour of the Tincture of Roses with many other Sulphureous Salts, as a
strong Solution of Pot-ashes, Oyl of Tartar, &c. which yet are seldome so
free from Feculency, as the Spirituous parts of Urine becomes by repeated
Distillation.

_Annotation_.

On this, occasion, I call to mind, that I found, a way of producing, though
not the same kind of Blew, as I have been mentioning, yet a Colour near of
Kin to it, namely, a fair Purple, by imploying a Liquor not made Red by
Art, instead of the Tincture of Red-roses, made with an Acid Spirit; And my
way was only to take Log-wood, (a Wood very well known to Dyers) having by
Infusion the Powder of it a while in fair Water made that Liquor Red, I
dropt into it a _Tantillum_ of an Urinous Spirit, as that of Sal-Armoniack,
(and I have done the same thing with an _Alcali_) by which the Colour was
in a moment turn'd into a Rich, and lovely Purple. But care must be had,
that you let not fall into a Spoonfull above two or three Drops, lest the
Colour become so deep, as to make the Liquor too Opacous. And (to answer
the other part of _Gassendus_ his Experiment) if instead of fair Water, I
infus'd the Log-wood in Water made somewhat sowr by the Acid Spirit of
Salt, I should obtain neither a Purple Liquor, nor a Red, but only a Yellow
one.

_EXPERIMENT XL._

The Experiment I am now to mention to you, _Pyrophilus_, is that which both
you, and all the other _Virtuosi_ that have seen it, have been pleas'd to
think very strange; and indeed of all the Experiments of Colours, I have
yet met with, it seems to be the fittest to recommend the Doctrine propos'd
in this Treatise, and to shew that we need not suppose, that all Colours
must necessarily be Inherent Qualities, flowing from the Substantial Forms
of the Bodies they are said to belong to, since by a bare Mechanical change
of Texture in the Minute parts of Bodies; two Colours may in a moment be
Generated quite _De novo,_ and utterly Destroy'd. For there is this
difference betwixt the following Experiment, and most of the others
deliver'd in these Papers, that in this, the Colour that a Body already
had, is not chang'd into another, but betwixt two Bodies, each of them
apart devoid of Colour, there is in a moment generated a very deep Colour,
and which if it were let alone, would be permanent; and yet by a very