11656An ESSAY
through I, and the Extremity of the propoſed
Line; and therefore the Perſpective of this Ex-
tremity is in the Line L H; which was to be
demonſtrated.
Line; and therefore the Perſpective of this Ex-
tremity is in the Line L H; which was to be
demonſtrated.
Note, if F H had been aſſumed, the one half,
or one third, & c. of what it is; then it is mani-
feſt that R Q muſt alfo have been taken 1119. to the one half, or third Part, & c. of C E.
or one third, & c. of what it is; then it is mani-
feſt that R Q muſt alfo have been taken 1119. to the one half, or third Part, & c. of C E.
Method. III.
71.
Forinclined Lines not meeting the Geometrical
Plane.
Plane.
Let A and B be the Seats of the Extremities of
22Fig. 37. the given Line. Let X repreſent a Plane paſſing
through the given Line perpendicular to the
Geometrical Plane. Likewiſe let M N in this
Plane, repreſent the Line whoſe Perſpective is re-
quir’d; and let C N and P M be perpendicular to
the Geometrical Plane: Whence P C repreſents
A B, and conſequently is equal thereto.
22Fig. 37. the given Line. Let X repreſent a Plane paſſing
through the given Line perpendicular to the
Geometrical Plane. Likewiſe let M N in this
Plane, repreſent the Line whoſe Perſpective is re-
quir’d; and let C N and P M be perpendicular to
the Geometrical Plane: Whence P C repreſents
A B, and conſequently is equal thereto.
Operation.
Find the Point I , the Perſpective of a 3350.
above the Point A, the Height of C N;
and
draw the Line B S, from the Point B, to the
Station Point I, cutting the Baſe Line in E; and
from the Point I, draw a Line to the accidental
Point F; which cut by a Perpendicular to the
Baſe Line, raiſed at the Point E; and then I T
will be the Appearance ſought.
draw the Line B S, from the Point B, to the
Station Point I, cutting the Baſe Line in E; and
from the Point I, draw a Line to the accidental
Point F; which cut by a Perpendicular to the
Baſe Line, raiſed at the Point E; and then I T
will be the Appearance ſought.
Method IV.
72.
For inclined Lines parallel to the perſpective
Plane.
Plane.