# Full text: Gravesande, Willem Jacob: An essay on perspective

on PERSPECTIVE. Sight to the Horizontal Line, equal in Length
to the principal Ray; and the Extremity of this
Perpendicular will be the Point ſought.

If nothing is determin’d, the Place of the Eye
may be taken at pleaſure in the Horizontal
Plane.

## 35. Method III.

29. The ſame Things being given as in the
precedent Method, about the Eye O, as a Cen-
ter; deſcribe the Arc of a Circle I H, touching
the Horizontal Line.

Fig. 9.

## 36. Operation .

About the given Point A, as a Center, de-
ſcribe the Arc of a Circle L C, touching the Baſe
Line: Then draw two Lines, C H and L I,
touching the two Circles L C and H I; and the
Point a, the Interſection of the ſaid two Lines,
will be the Appearance ſought.

## 37. Demonstration .

30. To demonſtrate this, draw the Line A B
perpendicular to the Baſe Line; O V perpendi-
cular to the Horizontal Line; and A C, O H
perpendicular to the Tangent H C. All theſe
Perpendiculars will cut the Lines to which they
are perpendicular, in the Points wherein theſe
laſt touch the Circle L B C, or H V I. Like-
wiſe draw the Line A E from the given Point
A, to the Point E, wherein the Line H C cuts
the Baſe Line. Finally, draw O D, from the
Eye O to the Point D, wherein the ſaid Line
HC cuts the Horizontal Line.

## Note to user

Dear user,

In response to current developments in the web technology used by the Goobi viewer, the software no longer supports your browser.