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



Wood, requesting him to say if he had any idea of the effects of 

 the kaleidoscope when he wrote those propositions. To this 

 letter Dr. B. received the following handsome and satisfactory 

 answer : 



" St. John's, May 19, 1 818. 

 " Sir, — The propositions I have given relating to the number 

 of images formed by plane reflectors inclined to each other, 

 contain merely the mathematical calculation of their number and 

 arrangement. The effects produced by the kaleidoscope were never 

 in my contemplation. My attention has for some years been 

 turned to other subjects, and I regret that I have not time to 

 read your Optical Treatise, which 1 am sure would give me great 

 pleasure. I am, Sir, your obedient humble servant, 



"J. Wood." 



The next supposed anticipation of the kaleidoscope was an 

 instrument proposed by Mr. Bradley in 1717. This instrument 

 consists of two large pieces of silvered looking-glass, Jive inches 

 icide and four inches high, jointed together with hinges, and 

 opening like a book. These plates being set upon a geometrical 

 drawing, and the eye being placed in front of the mirrors, the 

 lines of the drawing were seen multiplied by repeated reflections. 

 This instrument was described long before by Kircher, and did 

 not receive a single improvement from the hands of Bradley. It 

 has been often made by the opticians, and was principally used 

 for multiplying the human face, when placed between the 

 mirrors ; but no person ever thought of applying it to any pur- 

 pose of utility, or of using it as an instrument of rational amuse- 

 ment, by the creation of beautiful fonns. From the very 

 construction of the instrument, indeed, it is quite incapable of 

 producing any of the singular effects exhibited by the kaleido- 

 scope. It gives, indeed, a series of reflected images arranged 

 round a centre ; but so does a pair of looking-glasses placed 

 angularly in an apartment, and so do the pieces of mirror glass 

 with which jewellers multiply the wares exhibited at their 

 windows. It might, therefore, be as gravely maintained that 

 any of these combinations of mirrors was a kaleidoscope, as that 

 Bradley's pair of plates was an anticipation of that instrument. 

 As the similarity between the two has been maintained by 

 ignorant and interested individuals, we shall be at some pains to 

 explain to the reader the differences between these two instru- 

 ments ; and we shall do this, first, upon the supposition that the 

 two instruments are applied to geometric lines upon paper. 



1. In Bradley's instrument, 1. In the kaleidoscope, the 

 the length is less than the length of the plates must be 

 breadth of the plates. four, or five, or six times their 



breadth. 



2. Bradley's instrument can- 2. The kaleidoscope cannot 

 not be used with a tube. be used without a tube. 





