The Artist's Repository, Or, Encyclopedia of the Fine Arts (Band 2): Perspective, Architecture (London, 1808)

LECT. I.] QN PERSPECTIVE. 25

fair equable horizon. The courfe of rays (hot from
the eye, to the various parts of this horizon, is a level,
a plane of rays. A fan fpread open may illuftrate this
idea ; the handle may denote the eye ot a fpectator;
tbe circumference of the edge of the mount may re-
prefent the horizon, and the flicks are a level or plane
of rays iffuing from the eye to the circumference: or
they may be regarded as rays iffuing from the horizon,
and terminating in the pin or pivot, the center of the
handle : this ftatement is perhaps moft conformable
to Nature ; but for purpofes of Art, either fuppofition
may be adopted by way of explanation.

As I wifh to render this part of our fubject clear
and familiar, I (hall remind you of what we all have
obferved, occafionally, I might fay conflantlv. In en-
tering a houfe, at the level of the ftreet, we fuppofe
right before us is a Might of flairs : obferve thefe flairs ;
of fome, i. e. of the lower ones, we fee the whole
tread of the flair; of others, higher up in the flight,
we fee little or nothing of the tread ; of others, higher
flill, we fee no part of the tread, but, if the front of
the flair was away, we lhould fee under the tread of
the flair. Now each of thefe flairs may be taken to
reprefent a plane ; but it is evident, that only one of
them can be the true horizontal plane. If we proceed
up this flair-cafe, we obferve other planes prefenting
themfelves to our view, and each of them in our pro-
grefs, anfwering to the horizontal plane : our eye has
traced this—up the flairs—to the floor of the landing
place—to other flairs, flill higher—and fo on. In this
manner would the horizontal line correfpond to the
height of our eye, were we to afcend to the very top

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