Galilei, Galileo, The systems of the world, 1661

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1light in the extremities, than in the middle parts.
SALV. The doubt is ingenious and worthy of conſideration;
and as it but juſt now came into your mind unawares, ſo I will
like wiſe anſwer with what firſt comes into my thoughts, and it may
happily fall out, that by thinking more upon it, I may ſtumble
upon a better reply.
But before, that I labyrinth my ſelf any
ther, it would be neceſſary, that we aſſure our ſelves by ſome
periment, whether your objection prove in effect, what it ſeemeth
to conclude in appearance; and therefore taking once more the
ſame paper, and making it to incline, by bending a little part
thereof upon the remainder, let us try whether expoſing it to the
Sun, ſo that the rayes of light fall upon the leſſer part directly,
and upon the other obliquely; this which receiveth the rayes
ly appeareth more lucid; and ſee here by manifeſt experience,
that it is notably more clear.
Now if your objection be concluſive,
it will follow, that ſtooping with our eye ſo, that in beholding
the other greater part, leſs illuminated, in compreſſion or
ſhortning, it appear unto us no bigger than the other, more ſhining;
and that conſequently, it be not beheld at a greater angle than
that; it will neceſſarily enſue, I ſay, that its light be encreaſed, ſo
that it do ſeem to us as bright as the other.
See how I behold, and
look upon it ſo obliquely, that it appeareth to me narrower than
the other; but yet, notwithſtanding its obſcurity, doth not to
my perceiving, at all grow clearer.
Try now if the ſame ſucceed
to you.
SAGR. I have look't upon it, and though I have ſtooped with
my eye, yet cannot I ſee the ſaid ſuperficies encreaſe in light or
clarity; nay me thinks it rather grows more dusky.
SALV. We are hitherto confident of the invalidity of the
jection; In the next place, as to the ſolution, I believe, that, by
reaſon the Superficies of this paper is little leſſe than ſmooth, the
rayes are very few, which be reflected towards the point of
dence, in compariſon of the multitude, which are reflected
wards the oppoſite parts; and that of thoſe few more and more
are loſt, the nearer the viſive rayes approach to thoſe lucid rayes
of incidence; and becauſe it is not the incident rayes, but thoſe
which are reflected to the eye, that make the object appear
minous; therefore, in ſtooping the eye, there is more loſt than got,
as you your ſelf confeſſe to have ſeen in looking upon the
rer part of the paper.
SAGR. I reſt ſatisfied with this experiment and reaſon: It
mains now, that Simplicius anſwer to my other queſtion, and tell
me what moves the Peripateticks to require this ſo exact rotundity
in the Cœleſtial bodies.
SIMPL. The Cœleſtial bodies being ingenerable, inalterable,

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