=367. Multiple Reflection.=--If the light from an object is reflected by two or more mirrors various effects may be produced, as may be illustrated by the _kaleidoscope_. This consists of three plane mirrors so arranged that a cross-section of the three forms an equilateral triangle. The mirrors are placed in a tube across the end of which is a compartment with a translucent cover containing pieces of colored glass. On looking through the tube, the reflections from the several surfaces produce beautiful hexagonal designs. [Illustration: FIG. 357.--Perspective view of "Pepper's ghost."] [Illustration: FIG. 358.--Diagram of the "Pepper Ghost" illusion.] =368. Optical Illusions by a Plane Mirror.=--The _illusion_ called _Pepper's Ghost_ is typical of many illusions produced by reflection. It may be illustrated by taking a piece of plate glass, _M-N_, a tumbler of water, _W_, and a lighted candle, _C_, placed in a box, _B_, having one side open and arranged as shown in perspective in Fig. 357, and in section in Fig. 358. If the effect is produced in a darkened room, the observer at _E_ sees a virtual image of the lighted candle as if it were in the glass of water, the water being seen by transmitted light _through_ the plate glass, the latter forming a virtual image of the candle by reflection. Some of the illusions produced by this means are: (_a_) the figure suspended in mid air; (_b_) the bust of a person without a trunk; (_c_) the stage ghost; (_d_) the disappearing bouquet. [Illustration: FIG. 359.--Action of a concave mirror on parallel rays of light.] [Illustration: FIG. 360.--Real image formed by a concave mirror.]