15viiThe PREFACE.
This I have done ſometimes;
but it often
would have been very long and troubleſome.
In Geometry, the eaſieſt and ſhorteſt Way, is
not always that which leads to Diſcoveries.
would have been very long and troubleſome.
In Geometry, the eaſieſt and ſhorteſt Way, is
not always that which leads to Diſcoveries.
In the following Chapter, the Practice of Per-
ſpective upon the perſpective Plane, or Picture,
conſider’d as upright, is explain’d: Wherein,
among the different Ways laid down for the
Solution of general Problems, you will find
ſome effected by a Ruler only; ſo that after
ſome Preparations, all Kinds of Objects may
be drawn without Compaſſes, and that eaſier
than by the common Operations. In that
Problem, to find the Appearance of a Point
out of the Geometrical Plane, it is commonly
conſider’d as the Extremity of a Perpendicu-
lar, whoſe Repreſentation muſt first be found,
before that of the Point can be had. But here
we avoid this round-about Way, and ſhew how
to find the Appearance of the Point given,
without being obliged to find the Perſpective
of its Seat.
ſpective upon the perſpective Plane, or Picture,
conſider’d as upright, is explain’d: Wherein,
among the different Ways laid down for the
Solution of general Problems, you will find
ſome effected by a Ruler only; ſo that after
ſome Preparations, all Kinds of Objects may
be drawn without Compaſſes, and that eaſier
than by the common Operations. In that
Problem, to find the Appearance of a Point
out of the Geometrical Plane, it is commonly
conſider’d as the Extremity of a Perpendicu-
lar, whoſe Repreſentation muſt first be found,
before that of the Point can be had. But here
we avoid this round-about Way, and ſhew how
to find the Appearance of the Point given,
without being obliged to find the Perſpective
of its Seat.
As to the Appearance of a Cone and Cy-
linder, we determine the viſible Portions of
the Baſe, and by this means avoid the uſe-
leſs Operations which the common Way is
ſubject to. It is very difficult, if not impoſ-
ſible, to throw a Sphere into Perſpective, by
means of general Problems; and in the Re-
preſentation of the Torus of a Column, it
linder, we determine the viſible Portions of
the Baſe, and by this means avoid the uſe-
leſs Operations which the common Way is
ſubject to. It is very difficult, if not impoſ-
ſible, to throw a Sphere into Perſpective, by
means of general Problems; and in the Re-
preſentation of the Torus of a Column, it