Galilei, Galileo, The systems of the world, 1661

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1ſolar rays come: but it is true that by the vivacity of the light, the
ſaid
image will appear fringed about with many rays, and ſo will
ſeem
to occupie a far greater part of the plate, than really it doth.
And to ſhew that this is true, when you have noted the particular
place
of the plate from whence the reflection cometh, and
ved
likewiſe how great the ſhining place appeared to you, cover the
greater
part of that ſame ſpace, leaving it only viſible about the
midſt
; and all this ſhall not any whit diminiſh the apparent
dor
to one that beholds it from afar; but you ſhall ſee it largely
diſpers
'd upon the cloth or other matter, wherewith you covered
it
.
If therefore any one, by ſeeing from a good diſtance a ſmall
gilt
plate to be all over ſhining, ſhould imagine that the ſame
would
alſo even in a plate as broad as the Moon, he is no leſs
ceived
, than if he ſhould believe the Moon to be no bigger than
the
bottom of a tub.
If again the plate were turn'd into a
rical
ſuperficies, the reflection would be ſeen ſtrong in but one ſole
particle
of it; but yet by reaſon of its livelineſs, it will appear
fringed
about with many glittering rays: the reſt of the Ball would
appear
according as it was burniſhed; and this alſo onely then

when
it was not very much poliſhed, for ſhould it be perfectly
brightned
, it would appear obſcure.
An example of this we
have
dayly before our eyes in ſilver veſſels, which whilſt they are
only
boyl'd in the Argol and Salt, they are all as white as ſnow, and
do
not reflect any image; but if they be in any part burniſh'd, they
become
in that place preſently obſcure: and in them one may ſee the
repreſentation
of any thing as in Looking-glaſſes.
And that
to
obſcurity, proceeds from nothing elſe but the ſmoothing and
plaining
of a fine grain, which made the ſuperficies of the ſilver
rough
, and yet ſuch, as that it reflected the light into all parts,
whereby
it ſeemed from all parts equally illuminated: which
ſmall
unevenneſſes, when they come to be exquiſitely plained by
the
burniſh, ſo that the reflection of the rays of incidence are all
directed
unto one determinate place; then, from that ſame place,
the
burniſh'd part ſhall ſhew much more bright and ſhining than
the
reſt which is onely whitened by boyling; but from all other
places
it looks very obſcure.
And note, that the diverſity of

ſights
of looking upon burniſh'd ſuperficies, occaſioneth ſuch
difference
in appearances, that to imitate and repreſent in picture,
v. g. a poliſh'd Cuirace, one muſt couple black plains with white,
one
ſideways to the other, in thoſe parts of the arms where the
light
falleth equally.

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