And generally I find, that
_Saline menstruums_ are most operative upon those colours that are Purple,
or have some degree of Purple in them, and upon the other colours much
less. The _spurious_ pulses that compose which, being (as I formerly noted)
so very neer the middle between the true ones, that a small variation
throws them both to one side, or both to the other, and so consequently
must make a vast mutation in the formerly appearing Colour.

* * * * *

Observ. XI. _Of _Figures_ observ'd in small Sand._

Sand generally seems to be nothing else but exceeding small Pebbles, or at
least some very small parcels of a bigger stone; the whiter kind seems
through the _Microscope_ to consist of small transparent pieces of some
_pellucid_ body, each of them looking much like a piece of _Alum_, or _Salt
Gem_; and this kind of Sand is angled for the most part irregularly,
without any certain shape, and the _granules_ of it are for the most part
flaw'd, through amongst many of them it is not difficult to find some that
are perfectly _pellucid_, like a piece of clear Crystal, and divers
likewise most curiously shap'd, much after the manner of the bigger
_Stiriae_ of Crystal, or like the small Diamants I observ'd in certain
Flints, of which I shall by and by relate; which last particular seems to
argue, that this kind of Sand is not made by the comminution of greater
transparent Crystaline bodies, but by the _concretion_ or _coagulation_ of
Water, or some other fluid body.

There are other kinds of courser Sands, which are browner, and have their
particles much bigger; these, view'd with a _Microscope_, seem much courser
and more _opacous_ substances, and most of them are of some irregularly
rounded Figures; and though they seem not so _opacous_ as to the naked eye,
yet they seem very foul and cloudy, but neither do these want curiously
transparent, no more than they do regularly figur'd and well colour'd
particles, as I have often found.

There are multitudes of other kinds of Sands, which in many particulars,
plainly enough discoverable by the _Microscope_, differ both from these
last mention'd kinds of Sands, and from one another: there seeming to be as
great variety of Sands, as there is of Stones. And as amongst Stones some
are call'd precious from their excellency, so also are there Sands which
deserve the same Epithite for their beauty; for viewing a small parcel of
_East-India_ Sand (