Annotation.

This Experiment may bring some Light to, and receive some from a couple of other Experiments, that I remember I have met with in the ingenious Gassendus’s Animadversions upon Epicurus’s Philosophy, whilst I was turning over the Leaves of those Learned Commentaries; (my Eyes being too weak to let me read such Voluminous Books quite thorough) And I the less scruple (notwithstanding my contrary Custom in this Treatise) to set down these Experiments of another, because I shall a little improve the latter of them, and because by comparing there with that which I have last recited, we may be assisted to Conjecture upon what account it is, that Oyl of Vitriol heightens the Tincture of Red-rose Leaves, since Spirit of Salt, which is a highly Acid Menstruum, but otherwise differing enough from Oyl of Vitriol, does the same thing.  Our Authors Experiments then, as we made them, are these; We took about a Glass-full of luke-warm Water, and in it immerg’d a quantity of the Leaves of Senna, and presently upon the Immersion there did not appear any Redness in the Water, but dropping into it a little Oyl of Tartar, the Liquor soon discover’d a Redness to the watchfull Eye, whereas by a little of that Acid Liquor of Vitriol, which is like the former, undeservedly called Oyl, such a Colour would not be extracted from the infused Senna.  On the other side we took some Red-rose Leaves dry’d, and having shaken them into a Glass of fair Water, they imparted to it no Redness, but upon the affusion of a little Oyl of Vitriol the Water was immediately turn’d Red, which it would not have been, if instead of Oyl of Vitriol, we had imployed Oyl of Tartar to produce that Colour:  That these were Gassendus his Experiments, I partly remember, and was assur’d by a Friend, who lately Transcribed them out of Gassendus his Book, which I therefore add, because I have not now that Book at hand.  And the design of Gassendus in these Experiments our Friend affirms to be, to prove, that of things not Red a Redness may be made only by Mixture, and the Varied position of parts, wherein the Doctrine of that Subtil Philosopher doth not a little Authorize, what we have formerly delivered concerning the Emergency and Change of Colours.  But the instances, that we have out of him set down, seem not to be the most Eminent, that may be produced of this truth:  For our next Experiment will shew the production of several Colours out of Liquors, which have not any of them any such Colour, nor indeed any discernable one at all; and whereas though our Author tells us, that there was no Redness either in the Water, or the Leaves of Senna, or the Oyl of Tartar; And though it be true, that the Predominant Colour of the Leaves of Senna be another than Red, yet we have try’d, that by steeping that Plant a Night even in Cold water, it would afford a very deep Yellow or Reddish Tincture without the help of the