_Authour_, that I can add nothing, but that of a multitude of trials that I
made, I have found them exactly to agree with his Rules and Theories; and
though there may be infinite instances, yet may they be reduc'd under a few
Heads, and compris'd within a very few Rules. 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
_Stiriæ_ 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.