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

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poie it to be, but perhaps its accuracy may
seem doubtful, when I proceed to say, that every
objebt appears on it inverfe; what is really
above, seems below; what is really to the
right hand, seems to the left.
This is very distinctly seen in the dissecled
eye of a large quadruped, an ox, or a horse :
but perhaps the same efifebt is more familiar to
my auditors, from observations I doubt not
j '
they must have made, on the transmission os
luminous rays through a small hole, or crevice,
into a dark chamber. In this case, external
■objebts, or the effects of external objebts, be-
come depibted on the opposite wall of the
chamber inverfely with re soe ft to the actual
situation of such objedbs s thus, if the perfora-
tion be next a street, the approach of passengers
is, as it were, announced by a ray which (trikes
the part oppcfite to that whereon they are situ-
£ed: for the supposed crevice being far too
small to afford passage for the rays emitted
from every part of an objebt, becomes a centre
to those rays whose different direbtions permit
them to converge. Theresore the ray from
above, continuing its natural course in a straight
line, necessarily falls below j as the ray from
below, necessarily ascends.
How then do we acquire the faculty of distin-
guishing