Salusbury, Thomas
,
Mathematical collections and translations (Tome I)
,
1667
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which being of a ſpherical figure, if its ſuperficies were ſmooth, as
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this paper, the parts of its hemiſphere illuminated by the Sun,
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which are towards its extremity, would receive much leſs light,
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than the middle parts; the rays falling upon them moſt obliquely,
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and upon theſe at right angles; whereupon at the time of full
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Moon, when we ſee almoſt its whole Hemiſphere illuminated, the
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parts towards the midſt, would ſhew themſelves to us with more
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ſplendor, than thoſe others towards the circumference: which is
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not ſo in effect. </
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>Now the face of the Moon being repreſented
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to me full of indifferent high mountains, do not you ſee how their
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tops and continuate ridges, being elevated above the convexity of
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the perfect ſpherical ſuperficies, come to be expoſed to the view
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of the Sun, and accommodated to receive its rays much leſs
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liquely, and conſequently to appear as luminous as the reſt?</
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The more oblique
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Rayes illuminate
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leß, and why.
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<
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>SAGR. </
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>All this I well perceive: and if there are ſuch
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tains, its true, the Sun will dart upon them much more directly
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than it would do upon the inclination of a polite ſuperficies: but
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it is alſo true, that betwixt thoſe mountains all the valleys would
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become obſcure, by reaſon of the vaſt ſhadows, which in that
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time would be caſt from the mountains, whereas the parts towards
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the middle, though full of valleys and hills, by reaſon they have
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the Sun elevated, would appear without ſhadow, and therefore
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more lucid by far than the extreme parts, which are no leſs
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ſed with ſhadow than light, and yet we can perceive no ſuch
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rence.</
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<
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>SIMPL. </
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>I was ruminating upon the like difficulty.</
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<
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>SALV. </
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>How much readier is
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Simplicius
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to apprehend the
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jections which favour the opinions of
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Ariſtotle,
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than their
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ons? </
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>I have a kind of ſuſpition, that he ſtrives alſo ſometimes to
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diſſemble them; and in the preſent caſe, he being of himſelf able
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to hit upon the doubt, which yet is very ingenious, I cannot
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lieve but that he alſo was adviſ'd of the anſwer; wherefore I will
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attempt to wreſt the ſame (as they ſay) out of his mouth. </
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fore tell me,
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Simplicius,
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do you think there can be any ſhadow,
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where the rays of the Sun do ſhine?</
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<
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>SIMPL. </
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>I believe, nay I am certain that there cannot; for that
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it being the grand luminary, which with its rays driveth away
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neſs, it is impoſſible any tenebroſity ſhould remain where it
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eth; moreover, we have the definition, that
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Tenebræ ſunt
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tio luminis.
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<
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>SALV. </
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>Therefore the Sun, beholding the Earth, Moon or
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ther opacous body, never ſeeth any of its ſhady parts, it not
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ving any other eyes to ſee with, ſave its rays, the conveyers of
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light: and conſequently, one ſtanding in the Sun would never
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ſee any thing of umbrage, foraſmuch as his viſive rays would ever </
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