358. Besides the mirrors described above, others of
different forms are sometimes constructed, but they
always form distorted images of objects. Of this kind
are cylindrical and coniqal mirrors, the names of which
sufficiently indicate their forms. The effect of a cylin-
drical mirror may be seen by taking a bright sheet of tin-
plate in the two hands, and slightly bending its two op-
posite sides backward, and observing the image of the
face in it. Every part of the face will appear of the full
length, but will be diminished in breadth, giving the
whole a ludicrous aspect. If the upper and lower sides
of the plate are bent backward, the reverse effect will be
produced ; the parts of the face will appear of the usual
breadth, but greatly diminished in length.
359. Anamorphoses, — Sometimes dis-
torted pictures of objects are made, so that
seen in one of these mirrors, all the parts
of the object shall appear in their true
pi:oportions. Thus, let A be a cylindri-
cal mirror, standing perpendicularly upon
the paper, and let the figure, B C D E, be
observed as it will be reflected from its
surface. It will then appear as a perfect
__ _ square, F, the distortion in the picture

Anamorpho8e8. being ucccssary to give it this form after
reflection from a cylindrical surface.
