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