There being therefore such a difference of density, and no Experiment yet known to prove a Saltus, or skipping from one degree of rarity to another much differing from it, that is, that an upper part of the Air should so much differ from that immediately subjacent to it, as to make a distinct superficies, such as we observe between the Air and Water, &c. But it being more likely, that there is a continual increase of rarity in the parts of the Air, the further they are removed from the surface of the Earth: It will hence necessarily follow, that (as in the Experiment of the salt and fresh Water) the ray of Light passing obliquely through the Air also, which is of very different density, will be continually, and infinitely inflected, or bended, from a streight, or direct motion.
This granted, the reason of all the above recited Phaenomena, concerning the appearance of the Celestial Bodies, will very easily be deduced. As,
First, The redness of the Sun, Moon, and Stars, will be found to be caused by the inflection of the rays within the Atmosphere. That it is not really in or near the luminous bodies, will, I suppose, be very easily granted, seeing that this redness is observable in several places differing in Longitude, to be at the same time different, the setting and rising Sun of all parts being for the most part red:
And secondly, That it is not meerly the colour of the Air interpos’d, will, I suppose, without much more difficulty be yielded, seeing that we may observe a very great interstitium of Air betwixt the Object, and the Eye, makes it appear of a dead blew, far enough differing from a red, or yellow.