* * * *

_An Observation of Optick Glasses made of _Rock-Chrystal_._

This is contained in a Letter of _Eustachio Divini_, Printed in _Italian_
at _Rome_, as the _39. Journal des Scavans_ extracts it, _vid._

[Sidenote: * It may be queried whether those were true Veins, or only
Superficial Strictures, and slight scratches.]

Though it be commonly believed, that _Rock-Christal_ is not fit for
Optick-Glasses, because there are many Veins in it; yet _Eustachio Divini_
made one of it, which _he saith_ proved an excellent one, though full of
Veins. *

* * * * *

_An Accompt of the Use of the Grain of _Kermes_ for Coloration._

This was communicated by the Ingenious Dr. _Croon_, as he received it from
one Monsieur _Verny_, a _French_ Apothecary at _Montpelier_; who having
described the Grain of _Kermes_, to be an excrescence growing upon the
Wood, and often upon the {363} leaves of a Shrub, plentifull in
_Languedock_, and gather'd in the end of _May_, and the beginning of
_June_, full of a red Juyce; subjoyns two Uses, which that Grain hath, the
one for _Medicine_, the other for _Dying of Wool_. Waving the _first_,
notice shall only be taken here of the _latter_, vid. That, for _Dying_,
they take the Grain of _Kermes_, when ripe, and spread it upon Linnen: And
at first, whilst it abounds most in moisture, 'tis turn'd twice or thrice a
day, to prevent its Heating. And when there appears red powder amongst it,
they separate it, passing it through a Searce; and then again spread abroad
the Grain upon Linnen, untill there be perceived the same redness of the
powder; and at the end, this red power appears _about_ and _on_ the surface
of the Grain, which is still to be pass'd through a Searce, till it render
no more.

And in the beginning, when the small red Grains are seen to move (as they
will do) they are sprinkled over with strong Vinegar, and rubb'd between
ones hands: afterwards little balls are form'd thereof, which are expos'd
to the Sun to dry.

If this red powder should be let alone, without pouring Vinegar or some
other accid liquor upon it, out of every Grain thereof would be form'd a
little Fly, which would skip and fly up and down for a day or two, and at
last changing its colour, fall down quite dead, deprived of all the
bitterness, the Grains, whence they are generated, had before.

The Grain being altogether emptyed of its pulp or red powder, 'tis wash'd