7536An ESSAY
The Reaſon of this is evident, from the Demon-
ſtration of the upright Cone: For, it is manifeſt, that
X is the Seat of the Center of the Circle, which the
Cone continued forms in the Horizontal Plane; and
conſequently, the Point s, in regard to the Circle BED,
is in the ſame Situation as the Eye is, in reſpect of
the Interſection of the continued Cone, and the Hori-
zontal Plane.
ſtration of the upright Cone: For, it is manifeſt, that
X is the Seat of the Center of the Circle, which the
Cone continued forms in the Horizontal Plane; and
conſequently, the Point s, in regard to the Circle BED,
is in the ſame Situation as the Eye is, in reſpect of
the Interſection of the continued Cone, and the Hori-
zontal Plane.
Problem VII.
55. To find the Perſpective of a Line, perpendicular
to the Geometrical Plane.
to the Geometrical Plane.
Aſſume E D, any where in the Baſe Line,
equal to B C; and from the Points D and E,
draw D F and E F to ſome Point F, taken at
pleaſure in the Horizontal Line. Then having
found a, the Repreſentation of the Point A; 2222. draw a H parallel to the Baſe Line, and aI per-
pendicular thereto: And if aI be made equal to
G H, the ſaid a I will be the Perſpective
ſought.
equal to B C; and from the Points D and E,
draw D F and E F to ſome Point F, taken at
pleaſure in the Horizontal Line. Then having
found a, the Repreſentation of the Point A; 2222. draw a H parallel to the Baſe Line, and aI per-
pendicular thereto: And if aI be made equal to
G H, the ſaid a I will be the Perſpective
ſought.