Blew, Green, Yellow, Red, Purple, Green_.]

5. The _Atomists_ of Old, and some Learned men of late, have attempted to
explicate the variety of Colours in Opacous bodies from the various Figures
of their Superficial parts; the attempt is Ingenious, and the Doctrine
seems partly True, but I confess I think there are divers other things that
must be taken in as concurrent to produce those differing forms of
Asperity, whereon the Colours of Opacous bodies seem to depend. To declare
this a little, we must assume, that the Surfaces of all such Bodies how
Smooth or polite soever they may appear to our Dull Sight and Touch, are
exactly smooth only in a popular, or at most in a Physical sense, but not
in a strict and rigid sense.

6. This, excellent _Microscopes_ shew us in many Bodies, that seem Smooth
to our naked Eyes; and this not only as to the little Hillocks or
Protuberancies that swell above that which may be conceiv'd to be the Plain
or Level of the consider'd Surface, for it is obvious enough to those that
are any thing conversant with such Glasses, but as to numerous Depressions
beneath that Level, of which sort of Cavities by the help of a
_Microscope_, which the greatest Artificer that makes them, judges to be
the greatest Magnifying Glass in _Europe_, except one that equals it, we
have on the Surface of a thin piece of Cork that appear'd smooth to the
Eye, observ'd about sixty in a Row, within the length of less then an 31
and 32 part of an Inch, (for the Glass takes in no longer a space at one
view) and these Cavities (which made that little piece of Cork look almost
like an empty Honey-comb) were not only very distinct, and figur'd like one
another, but of a considerable bigness, and a scarce credible depth;
insomuch that their distinct shadows as well as sides were plainly
discern'd and easiy to be reckon'd, and might have been well distinguish'd,
though they had been ten times lesser than they were; which I thought it