the Degenerating of Blew into Red is uſual enough, but the turning of Red into Blew is very unfrequent. If at every drop of Spirit of Urine you ſhake the Vial containing the Red Tincture, you may delightfully obſerve a pretty variety of Colours in the paſſage of that Tincture from a Red to a Blew, and ſometimes we have this way hit upon ſuch a Liquor, as being look't upon againſt and from the Light, did ſeem faintly to emulate the above-mention'd Tincture of Lignum Nephriticum. And if you make the Tincture of Red-roſes very high, and without Diluting it with fair Water, pour on the Spirit of Urine, you may have a Blew ſo deep, as to make the Liquor Opacous, but being dropt upon White Paper the Colour will ſoon diſcloſe it ſelf. Alſo having made the Red, and conſequently the Blew Tincture very Tranſparent, and ſuffer'd it to reſt in a ſmall open Vial for a Day or two, we found according to our Conjecture, that not only the Blew but the Red Colour alſo was Vaniſh'd; the clear Liquor being of a bright Amber Colour, at the bottom of which ſubſided a Light, but Copious feculency of almoſt the ſame Colour, which ſeems to be nothing but the Tincted parts of the Roſe Leaves drawn out by the Acid
Spirits of the Oyl of Vitriol, and Precipitated by the Volatile Salt of the Spirit of Urine, which makes it the more probable, that the Redneſs drawn by the Oyl of Vitriol, was at leaſt as well an extraction of the 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 ſmall Parcel of a third Body, that has no Colour of its own, (leſt ſome may pretend I know not what Antipathy betwixt Colours) this otherwiſe permanent Colour will be in another trice ſo quite Deſtroy'd, that there will remain no foot-ſtepts either of it or of any other Colour in the whole Mixture.
The Experiment is very eaſie, and it is thus perform'd: Take good common Sublimate, and fully ſatiate with it what quantity of Water you pleaſe, Filtre the Solution carefully through clean and cloſe Paper, that it may drop down as Clear and Colourleſs as Fountain water. Then when you'l ſhew the Experiment, put of it about a Spoonfull into a ſmall Wine-glaſs, or any other convenient Veſſel made of clear Glaſs, and droping in three or four
drops of good Oyl of Tartar, per Deliquium; well Filtred that it may likewiſe be without Colour, theſe two Limpid Liquors will in the twinkling of an Eye turn into an Opacous mixture of a deep Orange Colour, which by keeping the Glaſs continually ſhaking in your hand, you muſt preſerve from ſetling too ſoon to the Bottom; And when the Spectators have a little beheld this firſt Change, then you muſt preſently drop in about four or five drops of Oyl of Vitriol, and continuing to ſhake the Glaſs pretty ſtrongly, that it may the Nimbler diffuſe it ſelf, the whole Colour, if you have gone Skilfully to work, will immediately diſappear, and all the Liquor in the Glaſs will be Clear and Colourleſs as before, without ſo much as a Sediment at the Bottom. But for the more gracefull Trial of this Experiment, 'twill not be amiſs to obſerve, Firſt, That there ſhould not be taken too much of the Solution of Sublimate, nor too much of the Oyl of Tartar drop'd in, to avoid the neceſſity of putting in ſo much Oyl of Vitriol as may make an Ebullition, and perhaps run over the Glaſs. Secondly, That 'tis convenient to keep the Glaſs always a little ſhaking, both for the better mixing of the Liquors, and to keep the Yellow Subſtance from Subſiding, which