14671on PERSPECTIVE.
Remark.
It is manifeſt , that T R may be 1119.
equal to {1/2} or {1/3} &
c.
of what it is taken here,
provided likewiſe that then D N be aſſumed
equal to a correſpondent Part of the propoſed
Line.
provided likewiſe that then D N be aſſumed
equal to a correſpondent Part of the propoſed
Line.
Problem IV.
87.
To throw a Sphere into Perſpective.
The Method of ſolving this Problem before
laid down , muſt be uſed here, but with 2263. Difference; that inſtead of uſing the Point of
Sight, the Point wherein a Perpendicular drawn
from the Eye to the perſpective Plane, meets
the ſaid Plane, muſt be uſed. And you muſt
obſerve, that this Perpendicular meaſures the
Eye’s Diſtance from the perſpective Plane.
laid down , muſt be uſed here, but with 2263. Difference; that inſtead of uſing the Point of
Sight, the Point wherein a Perpendicular drawn
from the Eye to the perſpective Plane, meets
the ſaid Plane, muſt be uſed. And you muſt
obſerve, that this Perpendicular meaſures the
Eye’s Diſtance from the perſpective Plane.
Problem V.
88.
To find the accidental Point of any Number
33Fig. 48. of Lines inclined to the Geometrical Plane.
33Fig. 48. of Lines inclined to the Geometrical Plane.
Let A B be the Direction of one of the in-
clined Lines, O the Eye in the Horizontal Plane,
and S the Station Point.
clined Lines, O the Eye in the Horizontal Plane,
and S the Station Point.
Operation.
Draw the Line O D, thro’ the Eye O parallel
to A B, meeting the Horizontal Line in D, which
will be the Accidental Point of the 4413, 14. of the given Line; and thro’ the Station Point
to A B, meeting the Horizontal Line in D, which
will be the Accidental Point of the 4413, 14. of the given Line; and thro’ the Station Point