60 History of Dr. Brewster's Kaleidoscope. [July, 



was an even or an odd aliquot part of a circle, when the object 

 was regular; or the even aliquot part of a circle when the object 

 was irregular. 



2. That out of an infinite number of positions for the object 

 both within and without the reflectors, there was only one position 

 where perfect symmetry could be obtained, namely, by placing 

 the object in contact with the ends of the reflectors. 



3. That out of an infinite number of positions of the eye, 

 there was only one where the symmetry was perfect, namely, as 

 near as possible to the angular point, so that the circular field 

 could be distinctly seen ; and that this point was the only one 

 out of an infinite number at which the uniformity of the light of 

 the circular field was a maximum. 



Upon these principles Dr. B. constructed an instrument, in 

 which he fixed permanently across the ends of reflectors pieces 

 of coloured glass, and other irregular objects, and he showed 

 the instrument in this state to some members of the Royal 

 Society of Edinburgh, who were much struck with the beauty of 

 its effects. In this case, however, the forms were nearly perma- 

 nent, and a slight variation was produced by varying the position 

 of the instrument, with respect to the light. The great step, 

 however, towards the completion of the instrument remained yet 

 to be made ; and it was not till some lime afterwards that the 

 idea occurred to Dr. B. of giving motion to objects, such as pieces 

 of coloured glass, 8fc. which were either jixed or placed loosely in a 

 cell at the end of the instrument. When this idea was carried into 

 execution, the kaleidoscope, in its simple form, was completed. 



In this state, however, the kaleidoscope could not be consi- 

 dered as a general philosophical instrument of universal applica- 

 tion ; for it was incapable of producing beautiful forms unless the 

 object was nearly in perfect contact with the end of the reflectors. 



The next, and by far the most important step of the invention, 

 was therefore to remove this limitation by employing a draw 

 tube and lens, by means of which beautiful forms could be 

 created from objects of all sizes, and at all distances from the 

 observer. In this way the power of the kaleidoscope was indefi- 

 nitely extended, and every object in nature could be introduced 

 into the picture in the same manner as if these objects had been 

 reduced in size, and actually placed at the end of the reflectors. 



When the instrument was brought to this state of perfection, 

 Dr. Brewster was urged by his friends to secure the exclusive 

 property of it by a patent ; and he accordingly took out a patent 

 for " A New Optical Instrument for creating and exhibiting 

 beautiful Forms." In the specification of his patent he describes 

 the kaleidoscope in two different forms. The first consists of 

 two reflecting planes, put together according to the principles 

 already described, and placed in a tube, with an eye-hole in the 

 particular position which gives symmetry and a maximum uni- 

 formity of light, and with objects such as coloured glass, placed 



o 



