3211on PERSPECTIVE.
For the Horizontal Plane, is parallel to the
Geometrical Plane.
Geometrical Plane.
Corollary III.
16.
The Repreſentations of all Lines parallel to
the ſtation Line, concur in the Point of Sight.
the ſtation Line, concur in the Point of Sight.
This follows, becauſe the principal Ray is
parallel to the ſaid Lines.
parallel to the ſaid Lines.
Corollary IV.
17.
Two or more equal Lines being perpendicular,
or equally inclined the ſame Way, to the ſame Line pa-
rallel to the Station Line, have their Repreſentations
concurring in the principal Point.
or equally inclined the ſame Way, to the ſame Line pa-
rallel to the Station Line, have their Repreſentations
concurring in the principal Point.
Becauſe all theſe Lines are parallel and equal,
the Line paſſing through their Vertices, is pa-
rallel to that paſſing through their Baſes, and
this being parallel to the Station Line, it fol-
lows, that the Appearances of the ſaid 1116. and parallel Lines concur in the principal
Point.
the Line paſſing through their Vertices, is pa-
rallel to that paſſing through their Baſes, and
this being parallel to the Station Line, it fol-
lows, that the Appearances of the ſaid 1116. and parallel Lines concur in the principal
Point.
Theorem V.
18.
The Appearance of an indefinite Line does not
alter, when the Eye moves in a Line parallel to a
propoſed Line.
alter, when the Eye moves in a Line parallel to a
propoſed Line.
The Repreſentation of this Line, is the In-
terſection of the perſpective Plane, and a Plane
paſſing through the Eye and the ſaid Line. Now
the Eye remains in the ſame Plane, when it
moves in a Line parallel to the propoſed Line;
and conſequently the Appearance of this laſt
Line, will not be changed by that Motion.
terſection of the perſpective Plane, and a Plane
paſſing through the Eye and the ſaid Line. Now
the Eye remains in the ſame Plane, when it
moves in a Line parallel to the propoſed Line;
and conſequently the Appearance of this laſt
Line, will not be changed by that Motion.
Note, This Demonſtration doth not extend
to any particular Part of the given Line, but on-
ly to the Line in general.
to any particular Part of the given Line, but on-
ly to the Line in general.
zoom in
zoom out
zoom area
full page
page width
set mark
remove mark
get reference
digilib