not amiss to mention to you _Pyrophilus_ upon the by, that you may thence
make some Estimate, what a strange Inequality, and what a multitude of
little Shades, there may really be, in a scarce sensible part of the
Physical superficies, though the naked Eye sees no such matter. And as
Excellent _Microscopes_ shew us this Ruggedness in many Bodies that pass
for Smooth, so there are divers Experiments, though we must not now stay to
urge them, which seem to perswade us of the same thing as to the rest of
such Bodies as we are now treating off; So, that there is no sensible part
of an Opacous body, that may not be conceiv'd to be made up of a multitude
of singly insensible Corpuscles, but in the giving these surfaces that
disposition, which makes them alter the Light that reflects thence to the
Eye after the manner requisite to make the Object appear Green, Blew, &c.
the Figures of these Particles have _a great_, but not _the only_ stroak.
'Tis true indeed that the protuberant Particles may be of very great
variety of Figures, Sphærical, Elliptical, Conical, Cylindrical,
Polyedrical, and some very irregular, and that according to the Nature of
these, and the situation of the Lucid body, the Light must be variously
affected, after one manner from Surfaces (I now speak of Physical Surfaces)
consisting of Sphaerical, and in another from those that are made up of
Conical or Cylindrical Corpuscles; some being fitted to reflect more of the
incident Beams of Light, others less, and some towards one part, others
towards another. But besides this difference of Shape, there may be divers
other things that may eminently concurr to vary the forms of Asperity that
Colours so much depend on. For, willingly allowing the Figure of the
Particles in the first place, I consider secondly, that the superficial
Corpuscles, if I may so call them, may be bigger in one Body, and less in
another, and consequently fitted to allay the Light falling on them with
greater shades. Next, the protuberant Particles may be set more or less
close together, that is, there may be a greater or a smaller number of them
within the compass of one, than within the compass of another small part of