4218An ESSAY
and drawing a Line from the Point I to the
other Point of Diſtance; which, by its Inter-
ſection with E D, will give the Appearance of
the Point A.
other Point of Diſtance; which, by its Inter-
ſection with E D, will give the Appearance of
the Point A.
Method II.
26.
γ is the Horizontal Plane, X the Perſpe-
ctive Plane, Z the Geometrical Plane, O the Eye,
D C the Horizontal Line, B E the Baſe Line, and
A the given Point.
11Fig. 8.ctive Plane, Z the Geometrical Plane, O the Eye,
D C the Horizontal Line, B E the Baſe Line, and
A the given Point.
Operation.
Draw a Line from the Point A, to the Eye O, cut-
ting the Baſe Line in the Point B, and the Horizon-
tal Line in the Point C: Then aſſume B E in the
Baſe Line, equal to B A; and C D in the Hori-
zontal Line, equal to C O; and join the Points
E and D, by a Line cutting the Line A O in
the Point a; which will be the Appearance
ſought.
ting the Baſe Line in the Point B, and the Horizon-
tal Line in the Point C: Then aſſume B E in the
Baſe Line, equal to B A; and C D in the Hori-
zontal Line, equal to C O; and join the Points
E and D, by a Line cutting the Line A O in
the Point a; which will be the Appearance
ſought.
Demonstration.
27.
The Triangle O D C in the Horizontal
Plane, is ſimilar to the Triangle A B E in the
Geometrical Plane; and conſequently A B is pa-
rallel to O C, and A E to O D. But the Appear-
ance of A muſt be in the Lines B C, and E D; 2213. and therefore it will be in a, their Interſection.
Plane, is ſimilar to the Triangle A B E in the
Geometrical Plane; and conſequently A B is pa-
rallel to O C, and A E to O D. But the Appear-
ance of A muſt be in the Lines B C, and E D; 2213. and therefore it will be in a, their Interſection.
Remarks.
28.
If the Place wherein the Eye ought to be in
the Horizontal Plane be not known, but the Point
of Sight is; then, to find the Place of the Eye,
a Perpendicular muſt be rais’d from the Point
the Horizontal Plane be not known, but the Point
of Sight is; then, to find the Place of the Eye,
a Perpendicular muſt be rais’d from the Point