246An ESSAY
4.
The Repreſentation of a Line Parallel to the
11Fig. 3. perſpective Plane, is parallel to the Line whereof it is
the Repreſentation.
11Fig. 3. perſpective Plane, is parallel to the Line whereof it is
the Repreſentation.
Let A B be a Line Parallel to the perſpective
Plane; we are to prove that a b its Repreſentati-
on is Parallel thereto.
Plane; we are to prove that a b its Repreſentati-
on is Parallel thereto.
Theſe two Lines A B and a b, will never
meet each other, becauſe a b is in the perſpective
Plane, and A B is ſuppoſed parallel to the ſaid
Plane. But they are alſo in one and the ſame
Plane, becauſe a b is the Interſection of the per-
ſpective Plane, and the Plane O A B, paſſing
through the Eye and the Line A B; and there-
fore they are parallel between themſelves: Which
was to be demonſtrated.
meet each other, becauſe a b is in the perſpective
Plane, and A B is ſuppoſed parallel to the ſaid
Plane. But they are alſo in one and the ſame
Plane, becauſe a b is the Interſection of the per-
ſpective Plane, and the Plane O A B, paſſing
through the Eye and the Line A B; and there-
fore they are parallel between themſelves: Which
was to be demonſtrated.
Corollary II.