THE KALEIDOSCOPE. 



them, these reflections will not be as vivid as the direct view of 

 the space B c; nor will they, compared one with another, be 

 equally vivid. The reflections B c' and c' c" will be less vivid than 

 the object B c, but more so than the second reflections c' c'" and 

 c" c"". The third reflection c'" c"" would be less vivid than the 

 second c' c'" and c" c"", if it proceeded only from one glass as do 

 the latter. But it must be remembered that being the combined 

 reflection of both glasses, the loss of brightness by the multiplied 

 reflections of each glass is to some extent compensated. 



4. We have here supposed that the glasses are inclined at 60, 

 but they may be inclined at any angle which is an aliquot part of 

 360. Thus if they are inclined at 90, the circular space or field 

 of view round A will be divided into four angular parts, and the 

 same observations are applicable. If the glasses are inclined at 

 an angle of 45, the field of view will be divided into eight equal 

 angular spaces, seven of which will be filled by the reflections. 



From what has been here explained, the unequal brightness of 

 the angular spaces seen in the kaleidoscope will be understood. 

 If, as is most common, the angle of the glasses be 60, this is per- 

 ceptible, but if it be 45, the repeated reflections so reduce the 

 brightness as to impair the beauty of the effect. 



5. The effects of the kaleidoscope are very striking, in conse- 

 quence of the endless variety of which they are susceptible, even 

 with a single cell at the object end of the instrument ; but it may 

 be so arranged that several cells, including different collections 

 of coloured objects, may be provided, and may be changed one 

 for another, fitting on the end of the tube like the cover of the 

 object glass of a telescope. 



The effects of this pretty little optical contrivance have been 

 occasionally rendered useful in the industrial arts, in suggesting 

 patterns for carpets and other products of the loom. 



6. An amusing optical toy is represented in fig. 3, by means of 



which objects may be seen, notwithstanding the interposition of 

 any opaque screen between them and the eye. The rays proceed- 

 ing from the object P entering the tube d strike on the mirror I 



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