THE KALEIDOSCOPE. 



1 Origin of the name. 2. Structure of the instrument. 3. Its optical 

 effect. 4. Varieties of its form. 5. Its occasional use in the arts. 

 6. Another optical toy depending on two reflections. 



1. THIS pretty optical toy, which is named from three Greek 

 words, K a\ov etios (Kalon eidos), a beautiful form, and MOW 

 (skopeo) I see, depends upon the properties of the looking-glass. 



2. Two oblong slips of looking-glass, A ace, and AabB, fig. 1, are 

 placed edge to edge at A a, inclined to each other at an angle of 60. 



Fig. i. 



Thus placed, they are fixed in a tube of tin or brass of correspond- 

 ing size, one end view of which is shown in fig. 2, where the circle 

 A c B represents the tube, and A B and A c the edges of the plates 

 of glass. One end of the tube is covered by two discs of glass, 

 between which broken pieces of coloured glass or other transparent 

 coloured object are placed loosely, so that they can fall from side 

 to side, and take an infinite variety of casual arrangements. The 

 external disc is ground-glass, to prevent the view of external 

 objects disturbing the effect. The other end of the tube is covered 

 by a diaphragm, with a small eye-hole in its centre, through 

 which the observer looks at the coloured objects contained in the 

 cell at the other end. He not only sees these objects, but also 

 their reflection in each of the inclined glasses ; and when the angle 

 of inclination is 60, the object will be seen five times repeated in 

 positions regularly disposed round the line formed by the edges 

 at which the glasses touch each other. 



3. The angular space, B A c, included between the glasses, and 

 every object within it, will be seen reflected in each glass. Thus 

 B A c will be seen in the glass B A, as if it were repeated in the 



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