DOI Page / Citation link:
https://doi.org/10.11588/diglit.18733#0048
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not properly belong to the nature of perspedlive, though
they ssow from its principles.
No. V. Exhibits the nature of a cone of rays, as ilsu-
ing from an object to the eye of a spectator : is a trans-
parent medium or glass be supposed to be situated be-
tween his eye and the objedl; it is evident that the
point where any ray intersered that medium, would
represent to the eye a correspondent point of the original
objedl: and if the whole number of rays were thus
described on the glass, they would sorm a picture of the
objedl, corresponding exactly to its dimensions and
figure, and having the same esfedt to the spectator.
PLATE III.
No. I. Is intended to Ihew, that the rays which pass
molt dire Si ly through the pupil are molt vigorous in their
effects, vide Ledture I. page 21. In a very strong
light, the pupil admits few rays • but those very brilliant :
In obscurity, the pupil admits a much greater number
(being extended) and probably of equal, or nearly equal
force.
No. II. It is necessary to premise, that in explaining
the following examples, the terms perpendicular and
horizontal have no relation to the natural horizon, but
relate solely to the position of lines with respedt to
each other: thus the line I C is perpendicular (i. e. is at
right angles) to the line CL These figures like wife explain
many ot the terms adopted in treating on perspedlive. In
this example the upright plane is supposed transparent, and
the eye to be situated at I; a line drawn diredt from I, to
the plane sor pidlure) strikes it in C; which is therefore
the center. From I to C is termed the difiance of tire
1 ridiure 3
not properly belong to the nature of perspedlive, though
they ssow from its principles.
No. V. Exhibits the nature of a cone of rays, as ilsu-
ing from an object to the eye of a spectator : is a trans-
parent medium or glass be supposed to be situated be-
tween his eye and the objedl; it is evident that the
point where any ray intersered that medium, would
represent to the eye a correspondent point of the original
objedl: and if the whole number of rays were thus
described on the glass, they would sorm a picture of the
objedl, corresponding exactly to its dimensions and
figure, and having the same esfedt to the spectator.
PLATE III.
No. I. Is intended to Ihew, that the rays which pass
molt dire Si ly through the pupil are molt vigorous in their
effects, vide Ledture I. page 21. In a very strong
light, the pupil admits few rays • but those very brilliant :
In obscurity, the pupil admits a much greater number
(being extended) and probably of equal, or nearly equal
force.
No. II. It is necessary to premise, that in explaining
the following examples, the terms perpendicular and
horizontal have no relation to the natural horizon, but
relate solely to the position of lines with respedt to
each other: thus the line I C is perpendicular (i. e. is at
right angles) to the line CL These figures like wife explain
many ot the terms adopted in treating on perspedlive. In
this example the upright plane is supposed transparent, and
the eye to be situated at I; a line drawn diredt from I, to
the plane sor pidlure) strikes it in C; which is therefore
the center. From I to C is termed the difiance of tire
1 ridiure 3