Salusbury, Thomas, Mathematical collections and translations (Tome I), 1667

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SIMPL. Stay a little; for I juſt now remember, that I have
read
in a little modern tract, full of many novelties; “That this
ſecondary
light is not derived from the Stars, nor innate in the
Moon
, and leaſt of all communicated by the Earth, but that it is

received
from the ſame illumination of the Sun, which, the
ſtance
of the Lunar Globe being ſomewhat tranſparent,
trateth
thorow all its body; but more livelily illuminateth the
ſuperficies
of the Hemiſphere expoſed to the rays of the Sun:
and
its proſundity imbuing, and (as I may ſay) ſwallowing that
light
, after the manner of a cloud or chryſtal, tranſmits it, and
renders
it viſibly lucid.
And this (if I remember aright) he
proveth
by Authority, Experience and Reaſon; citing Cleomedes,
Vitellion
, Macrobius, and a certain other modern Author: and
adding
, That it is ſeen by experience to ſhine moſt in the days
neareſt
the Conjunction, that is, when it is horned, and is chiefly
bright
about its limb.
And he farther writes, That in the Solar
Ecclipſes
, when it is under the Diſcus of the Sun, it may be ſeen
tranſlucid
, and more eſpecially towards its utmoſt Circle.
And
in
the next place, for Arguments, as I think, he ſaith, That it not
being
able to derive that light either from the Earth, or from the
Stars
, or from it ſelf, it neceſſarily follows, that it cometh from
the
Sun.
Beſides that, if you do but grant this ſuppoſition, one
may
eaſily give convenient reaſons for all the particulars that
occur
.
For the reaſon why that ſecundary light ſhews more
lively
towards the outmoſt limb, is, the ſhortneſs of the ſpace
that
the Suns rays hath to penetrate, in regard that of the lines
which
paſs through a circle, the greateſt is that which paſſeth
through
the centre, and of the reſt, thoſe which are fartheſt from
it
, are always leſs than thoſe that are nearer.
From the ſame
principle
, he ſaith, may be ſhewn why the ſaid light doth not
much
diminiſh.
And laſtly, by this way the cauſe is aſſigned
whence
it comes, that that ſame more ſhining circle about the
utmoſt
edge of the Moon, is ſeen at the time of the Solar
clipſe
, in that part which lyeth juſt under the Diſcus of the Sun,
but
not in that which is beſide the Diſcus: which happeneth
becauſe
the rays of the Sun paſs directly to our eye, through the
parts
of the Moon underneath: but as for the parts which are
beſides
it, they fall beſides the eye.

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