It has been observ'd and confirm'd by the accuratest Observations of the
best of our modern Astronomers, that all the Luminous bodies appear above
the Horizon, when they really are below it. So that the Sun and Moon have
both been seen above the Horizon, whil'st the Moon has been in an Eclipse.
I shall not here instance in the great refractions, that the tops of high
mountains, seen at a distance, have been found to have; all which seem to
argue the Horizontal refraction, much greater then it is hitherto generally
believ'd.
I have further taken notice, that not onely the Sun, Moon and Starrs, and
high tops of mountains have suffer'd these kinds of refraction, but Trees,
and several bright Objects on the ground: I have often taken notice of the
twinkling of the reflections of the Sun from a Glass-window at a good
distance, and of a Candle in the night, but that is not so conspicuous, and
in observing the setting Sun, I have often taken notice of the tremulation
of the Trees and Bushes, as well as of the edges of the Sun. Divers of
these _Phaenomena_ have been taken notice of by several, who have given
several reasons of them, but I have not yet met with any altogether
satisfactory, though some of their conjectures have been partly true, but
partly also false. Setting my self therfore upon the inquiry of these
_Phaenomena_, I first endeavour'd to be very diligent in taking notice of
the several particulars and circumstances observable in them; and next, in
making divers particular Experiments, that might cleer some doubts, and
serve to determine, confirm, and illustrate the true and adaequate cause of
each; and upon the whole, I find much reason to think, that the true cause
of all these _Phaenomena_ is from the _inflection_, or _multiplicate
refraction_ of those Rays of light within the body of the _Atmosphere_, and
that it does not proceed from a _refraction_ caus'd by any terminating
_superficies_ of the Air above, nor from any such exactly defin'd
_superficies_ within the body of the _Atmosphere_.
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