The artists repository and drawing magazine: exhibiting the principles of the polite arts in their various branches — 4.1790

Page: 151
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an improvement of nature itfelf, whereas the art of the
greater! mailer can only pretend to a diftant refemblance
and faint imitation. The reafcn why the image is co-
loured, is becaufe the feveral points of the object reflect-
ing feveral forts of coloured rays to the glafs, thofe rays
will give a reprefentation of thofe feveral points reflec-
tively, and in their own colour, and therefore in thofe
of the object; but thofe colours will be heightened,
becaufe they are crowded into a lefs fpace.

The fixthphenomenon is the Chiaro ofcuro, that is, the
intenflty of tight and foadow in the picture : And this,
as well as the colouring, is greatly heightened above
what it is in the object, by reafon of the lefier area of the
picture. Here every light and every made is exprejfed in
its proper degree, from the moft brilliant to the mofc
black, inclufive of a wonderful variety in the feveral
parts, arifing from the different fituations of the feveral
parts of the object, and the different angles of reflection.
A juft imitation of nature in the diftribution of light and
fhadows is perhaps the moft difficult part of the art of
painting, and on which its greateft perfection de-

N. B. If an object be placed juft: twice the focal
diftance from the glafs without, the image will be formed
at the fame diftance from the glafs within the room, and
confequently will be equal in magnitude to the object
itfelf. ' /

No. 2. is meant merely as a hint to explain the effects
of a lens behind the firftj for if the rays palling through
the firft are inverted^ by paffmg through a fecend they
will be re-inverted, if it be placed at a juft diftance with

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