The Theory and Practice of Perspective

by G. A. Storey

Fig. 296.

[ CLXVIII]

The Mirror at an Angle

If an object or line AB is inclined at an angle of 45° to the mirror RR, then the angle BAC will be a right angle, and this angle is exactly divided in two by the reflecting plane RR. And whatever the angle of the object or line makes with its reflection that angle will also be exactly divided.

Fig. 297.	Fig. 298.

Now suppose our mirror to be standing on a horizontal plane and on a pivot, so that it can be inclined either way. Whatever angle the mirror is to the plane the reflection of that plane in the mirror will be at the same angle on the other side of it, so that if the mirror OA (Fig. 298) is at 45° to the plane RR then the

reflection of that plane in the mirror will be 45° on the other side of it, or at right angles, and the reflected plane will appear perpendicular, as shown in Fig. 299, where we have a front view of a mirror leaning forward at an angle of 45° and reflecting the square aob with a cube standing upon it, only in the reflection the cube appears to be projecting from an upright plane or wall.