towards the _perpendicular_; whereas the air I
suppose to be a body that does more resist it, and consequently more are
_re-percuss'd_ then do enter it: the same kind of trials have I made, with
_Crystalline Glass_, with drops of fluid bodies, and several other ways,
which do all seem to agree very exactly with this _Theory_. So that from
this Principle well establish'd, we may deduce severall Corollaries not
unworthy observation.

And the first is; that it plainly appears by this, that the production of
the Rainbow is as much to be ascribed to the reflection of the concave
surface of the air, as to the refraction of the _Globular_ drops: this will
be evidently manifest by these Experiments, if you _foliate_ that part of a
Glass-ball that is to reflect an _Iris_, as in the _Cartesian_ Experiment,
above mention'd, the reflections will be abundantly more strong, and the
colours more vivid: and if that part of the surface be touch'd with Water,
scarce affords any sensible colour at all.

Next we learn, that the great reason why _pellucid_ bodies beaten small are
white, is from the multitude of reflections, not from the particles of the
body, but from the _contiguous_ surface of the air. And this is evidently
manifested, by filling the _Interstitia_ of those powder'd bodies with
Water, whereby their whiteness presently disappears. From the same reason
proceeds the whiteness of many kinds of Sands, which in the _Microscope_
appear to be made up of a multitude of little _pellucid_ bodies, whose
brightest reflections may by the _Microscope_ be plainly perceiv'd to come
from their internal surfaces; and much of the whiteness of it may be
destroy'd by the affusion of fair Water to be contiguous to those surfaces.

The whiteness also of froth, is for the most part to be ascribed to the
reflection of the light from the surface of the air within the Bubbles, and
very little to the reflection from the surface of the Water it self: for
this last reflection does not return a quarter so many Rays, as that which
is made from the surface of the air, as I have certainly found by a
multitude of Observations and Experiments.

The whiteness of _Linnen_, _Paper_, _Silk_, &c. proceeds much from the same
reason, as the _Microscope_ will easily discover; for the Paper is made up
of an abundance of _pellucid_ bodies, which afford a very plentifull
reflection from within, that is, from the concave surface of the air
contiguous to its component