on PERSPECTIVE.
Perpendiculars f P, O H, muſt be let fall from

the Points f and O, on the Baſe Line, and the

Line P g drawn; then the Point V, wherein it

cuts the Perpendicular O H, is the Point of Sight

ſought, and the Parts O V, and V H determine

the Height and Diſtance of the Eye.

35. When the Appearance of a Point is known,

Let A be a Point in the Geometrical Plane,

and a its Repreſentation in the perſpective Plane,

it is requir’d to find the Appearance of the

Point B.

Fig. 11.

Without Compaſſes.

Draw a Line from the Point B to the Eye O,

and another from the Point E, wherein the

ſaid Line continued, cuts the Baſe Line, to the

Point A; then draw the Line E a, and where

it cuts B O, is the Point b ſought.

The Point E is its own Repreſentation; and

becauſe the Point a is the Repreſentation of A,

the Line E a is that of E A. Now ſince the

Point B is in the Line E A, the Appearance of

this Point will be likewiſe in E a, as alſo in
B O; therefore it is in b the Interſection of the

Lines E a, and B O.

27.

37. If the Point A be in the Line B O, or

the Line B A be parallel, or a very little inclined

to the Baſe Line, we cannot then uſe this Me-