tuff, but is much more clear and transparent, and much more curiously
shaped, and yet may be cleft and flak'd like the other _Selenitis_. But
fourthly, this stone has a property, which in respect of the _Microscope_,
is more notable, and that is, that it exhibits several appearances of
Colours, both to the naked Eye, but much more conspicuously to the
_Microscope_; for the exhibiting of which, I took a piece of
_Muscovy-glass_, and splitting or cleaving it into thin Plates, I found
that up and down in several parts of them I could plainly perceive several
white specks or flaws, and others diversly coloured with all the Colours of
the _Rainbow_; and with the _Microscope_ I could perceive, that these
Colours were ranged in rings that incompassed the white speck or flaw, and
were round or irregular, according to the shape of the spot which they
terminated; and the position of Colours, in respect of one another, was the
very same as in the _Rainbow_. The consecution of those Colours from the
middle of the spot outward being Blew, Purple, Scarlet, Yellow, Green;
Blew, Purple, Scarlet, and so onwards, sometimes half a score times
repeated, that is, there appeared six, seven, eight, nine or ten several
coloured rings or lines, each incircling the other, in the same manner as I
have often seen a very _vivid Rainbow_ to have four or five several Rings
of Colours, that is, accounting all the Gradations between Red and Blew for
one: But the order of the Colours in these Rings was quite contrary to the
primary or innermost _Rainbow_, and the same with those of the secondary or
outermost Rainbow; these coloured Lines or _Irises_, as I may so call them,
were some of them much brighter then others, and some of them also very
much broader, they being some of them ten, twenty, nay, I believe, neer a
hundred times broader then others; and those usually were broadest which
were neerest the center or middle of the flaw. And oftentimes I found, that
these Colours reacht to the very middle of the flaw, and then there
appeared in the middle a very large spot, for the most part, all of one
colour, which was very vivid, and all the other Colours incompassing it,