Catoptrics, is that part of science which treats of the laws and properties of light reflected from mirrors or specula. The whole doctrine of catoptrics depends on this simple principle, namely, that the angle of incidence is equal to the angle of reflection.

Catoptric Cistula. An arrangement of mirrors in a kind of box, by which objects are represented as multiplied, magnified, or deformed. A variety of pleasing phenomena are exhibited by machines of this kind.

Catoptric, or Reflecting Dial, is a kind of dial which shows the hours by means of a piece of looking-glass plate, adjusted to reflect the solar rays upwards to the ceiling of a room, on which the hour lines are delineated.

Catoptric Telescope. Instead of lenses, this telescope is furnished chiefly with mirrors, and exhibits remote objects by reflection instead of refraction.

Fig. 1.

Catoptrics 329

Fig. 2.

Catoptrics 330