vapours, or the like) shall chance to be elevated into those
parts, will reflect a red towards the eye; and therefore those evenings and
mornings appear reddest, that have the most store of vapours and halituous
substances exhaled to a convenient distance from the Earth; for thereby the
inflection is made the greater, and thereby the colour also the more
intense; and several of those exhalations being opacous, reflect several of
those Rays, which, through an _Homogeneous_ transparent _medium_ would pass
unseen; and therefore we see, that when there chances to be any clouds
situated in those Regions they reflect a strong and vivid red. Now, though
one great cause of the redness may be this inflection, yet I cannot wholly
exclude the colour of the vapours themselves, which may have something of
redness in them, they being partly nitrous; and partly fuliginous; both
which steams tinge the Rays that pass through them, as is made evident by
looking at bodies through the fumes of _Aqua fortis_ or spirit of _Nitre_
[as the newly mentioned Illustrious Person has demonstrated] and also
through the smoak of a Fire or Chimney.

Having therefore made it probable at least, that the morning and evening
redness may partly proceed from this inflection or refraction of the Rays,
we shall next shew how the Oval Figure will be likewise easily deduced.

Suppose we therefore, EFGH in the sixth _Figure_ of the 37. _Scheme_, to
represent the Earth; ABCD, the _Atmosphere_; EI, and EL, two Rays coming
from the Sun, the one from the upper, the other from the neather Limb,
these Rays, being by the _Atmosphere_ inflected, appear to the eye at E, as
if they had come from the points, N and O; and because the Ray L has a
greater inclination upon the inequality of the _Atmosphere_ then I,
therefore must it suffer a greater inflection, and consequently be further
elevated above its true place, then the Ray I, which has a less
inclination, will be elevated above its true place; whence it will follow,
that the lower side appearing neerer the upper then really it is, and the
two _lateral_ sides, _viz._ the right and left side, suffering no sensible
alteration from the inflection, at least what it does suffer, does rather
increase the visible Diameter then diminish it, as I shall shew by and by,
the Figure of the luminous body must necessarily appear somewhat
_Elliptical_.

This will be more plain, if in the seventh _Figure_ of the 37. _Scheme_ we
suppose