The artists repository and drawing magazine: exhibiting the principles of the polite arts in their various branches (3.1789)

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will with the utmost propriety form an early
subjeCt in this discourse. Give me leave,
therefore, to requefi: your attention, while I
endeavour to explain some os the principles
which regulate this admirable faculty.
As I am not offering my remarks as an
Anatomist, or as an Optician, I shall consider the
Eye as composed of (i) the cornea, or extern
nal part, which by its projection enables the
pupil to receive a much greater quantity of
vision than it would if level with the surround-
ing parts of the ball. (2) The pupil ; this you
know. Ladies and Gentlemen, is an orifice
in the centre of the iris, through which the
rays of light pass into a very clear and tranf-
parent medium, called the chrystalline hu-
mour ; here they are converged into a focus,
and again diverged till they ssrike that part of
the retina whereto their direction inclines
them. (3) The retina is a very elaborate
collection of (apparent) net-work, furnished
with nerves; by whole motions the brain, or
seat of sensation, receives insormation of all that
passes without. Objects are pourtrayea on the
retina in their proper colours, and forms, nd
with their just degrees of force; so that it be-
comes an accurate and vivid picture of whatever
■is transmitted by the pupil. Vivid you may sup-
pose