Full text: Wilkins, John: A discovery of a new world

That the Moon may be a World. the Eaſt to be altered with the leaſt Light,
they would by the Situation of the Stars
find how many degrees the Sun was below the
Horizon, which was uſually about 18. From
whence they would eaſily conclude, how high
that Air muſt be above us, which the Sun could
ſhine upon, when he was 18 Degrees below
us. And from this obſervation it was conclu-
ded to be about 52 Miles high.

43.1.

Vitel. l. 10;
Theo. 7.

But in this Concluſion, the Antients were
much deceived, becauſe they proceeded on a
wrong ground, whilſt they ſuppoſed that the
ſhining of the Suns direct Rays upon the Air
was the only reaſon of Grepuſculum; whereas
’tis certain that there are many other things
which may alſo concur to the cauſing of it. As,

43.1.

Keplar. Ep.
Coper. l. 1.
part. 3.

1. Some bright Clouds below the Horizon,
which being illuminated by the Sun, may be
the means of conveying ſome Light to our Air,
before the direct Rays can touch it.

2. The often refraction of the Rays, which
ſuffer a frequent Repercuſſion from the Cavi-
ty of this Sphere, may likewiſe yield us ſome
Light.

3. And ſo may the Orb of enlightned Air
compaſſing the Sun, part of which muſt riſe
before his Body.

2. The ſecond way whereby we may more
ſurely ſind the Altitude of this groſſer Air, is
by taking the higheſt Cloud: which may be
done, 1. Either as they uſe to meaſure the
Altitude of things that cannot be approached
unto, viz. by two Stations, when two Perſons
ſhall at the ſame time, in ſeveral places, ob-
ſerve the Declination of any Cloud from the

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