16379on PERSPECTIVE.
dicular is on one Side or other of the perſpective
Plane with reſpect to the Eye. And the Line
paſſing through the Extremities of the ſaid Pa-
rallels, will determine the Repreſentation ſought,
by its interſecting the Line T a, as is evident by
what is demonſtrated.
Plane with reſpect to the Eye. And the Line
paſſing through the Extremities of the ſaid Pa-
rallels, will determine the Repreſentation ſought,
by its interſecting the Line T a, as is evident by
what is demonſtrated.
Method III.
97.
To find the Repreſentation of ſeveral Perpen-
diculars equal in Length to ſome one, whoſe Per-
ſpective is already drawn.
diculars equal in Length to ſome one, whoſe Per-
ſpective is already drawn.
Let H I, be the Perſpective of a Perpendicular
11Fig. 52. to the Geometrical or Perſpective Plane. Now
about the accidental Point T, as a Center, and
with the Radius T H, deſcribe the circular Arc
H G, whoſe Chord let be equal to H I, and draw
the indefinite Line TGC, and let a and b, re-
preſent the Feet of the Perpendiculars, whoſe
Repreſentations are requir’d.
11Fig. 52. to the Geometrical or Perſpective Plane. Now
about the accidental Point T, as a Center, and
with the Radius T H, deſcribe the circular Arc
H G, whoſe Chord let be equal to H I, and draw
the indefinite Line TGC, and let a and b, re-
preſent the Feet of the Perpendiculars, whoſe
Repreſentations are requir’d.
Operation.
Deſcribe about the Center T, the Arcs b F E,
and a DC, paſſing through the Points a and b, and
draw the Lines T b and T a; in each of which
aſſume b L equal to E F, and a X equal to C D;
and the ſought Repreſentations will be had.
and a DC, paſſing through the Points a and b, and
draw the Lines T b and T a; in each of which
aſſume b L equal to E F, and a X equal to C D;
and the ſought Repreſentations will be had.
Demonstration.
If H I, and a X repreſent Perpendiculars of
the ſame Length, it follows from the Demon-
ſtration of the precedent Method, that I H is to
H T, and a X to a T as the Difference of the
ſaid Perpendiculars, and Height of the Eye,
the ſame Length, it follows from the Demon-
ſtration of the precedent Method, that I H is to
H T, and a X to a T as the Difference of the
ſaid Perpendiculars, and Height of the Eye,
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