History of the Kaleidoscope. 451 



" From both tliese contrivances, and from every optical in- 

 strument with which I am acquainted, the kaleidoscope appears 

 to differ essentially both in its effect and in the principles of its 

 construction. 



" As to the effect, the thing produced by the kaleidoscope is 

 a series of figures presented with the most perfect sj'mmetry, so 

 as always to compose a whole, in which nothing is wanting and 

 nothing redundant. It matters not what the object be to which 

 the instrument is directed: if it only be in its proper place, the 

 effect just described is sure to take place, and with an endless 

 variety. In this respect, the kaleidoscope appears to be quite 

 singular among optical instruments. Neither the instrument of 

 Bradley, nor the experiment or theorem in Wood's book, have 

 any resemblance to this ; they go no further than the multipli- 

 cation of the figure. 



" Next, as to the principle of construction, Dr. Brewster's 

 instrument requires a particular position of the eye of the ob- 

 server, and of the object looked at, in order to its effect. If 

 either of these is wanting, the symmetry vanishes, and the figures 

 are irregular and disunited. In the other two cases, no parti- 

 cular position, either for the eye or the object, is required. 



" For these reasons. Dr. Brewster's invention seems to me 

 quite unlike the other two. Indeed, as far as I know, it is quite 

 singular among optical instruments ; and it will be matter of 

 sincere regret, if any imaginary or vague analogy between it 

 and other optical instruments, should be the means of depriving 

 the Doctor of any part of the reward to which his skill, inge- 

 nuity, and perseverance, entitle him so well. 



" John Plavfair, 



" Professor of Natural Philosophy in 

 the University of Edinburgh. 



" P. S. — Granting that there were a resemblance between the 

 kaleidoscope and Bradley's instrument, in any of the particu- 

 lars mentioned above, the introduction of coloured and move- 

 able objects, at the end of the reflectors, is quite peculiar to Dr. 

 Brewster's instrument. Besides this, a circumstance highly de- 

 serving of attention, is the use of two lenses and a draw tube, 

 so that the action of the kaleidoscope is extended to objects of 

 all sizes, and at all distances from the observer, and united, by 

 that means, to the advantages of the telescope. J. P." 



Professor Pictet's opinion is stated in the following letter : 

 "Sir, — Among your friends, I have not been one of the least 

 painfully affected by the shameful invasion of your rights as an 

 inventor, which I have been a witness of lately in London. Not 

 only none of the allegations of the invaders of your patent, 

 grounded on a protended similarity between vour kaleidoscope 



l'f2' ' and 



