1818.] History of Dr. Brewster's Kaleidoscope 59 



Hoping these suggestions will lead to the improvement of the 

 articles made of steel, and that they may also induce other per- 

 sons, who may be possessed of processes not generally known, 

 to communicate them through your channel for the public good, 

 I have the pleasure to remain, Gentlemen, 



Your most obedient servant, 



Thomas Gill. 



Article IX. 



History of Dr. Brewster's Kaleidoscope, with Remarks on its 

 supposed Resemblance to other Combinations of plain Mirrors. 

 From a Correspondent.* 



As this instrument has excited great attention, both in this 

 country and on the Continent, the readers of the Annalswi\\ doubt- 

 less take some interest in the history of the invention. In the 

 year 1814, when Dr. Brewster was engaged in experiments on 

 the polarization of light by successive reflections between plates 

 of glass, which were published in the Phil. Trans, for 1815, and 

 honoured by the Royal Society of London with the Copley medal, 

 the reflectors were in some cases inclined to each other, and he 

 had occasion to remark the circular arrangement of the images 

 of a candle round a centre, or the multiplication of the sectors 

 formed by the extremities of the glass plates. In repeating, at 

 a subsequent period, the experiments of M. Biotonthe action of 

 fluids upon light, Dr. B. placed the fluids in a trough formed by 

 two plates of glass cemented together at an angle. The eye 

 being necessarily placed at one end, some of the cement which 

 had been pressed through between the plates appeared to be 

 arranged into a regular figure. The symmetry of this figure 

 being very remarkable, Dr. B. set himself to investigate the 

 cause of the phenomenon ; and in doing this he discovered the 

 leading principles of the kaleidoscope. He found that in order 

 to produce perfectly beautiful and symmetrical forms, three con- 

 ditions were necessary. 



1. That the reflectors should be placed at an angle, which 



* In Jhe last number of the Annnh (p. 451), we inserted some remarks upon 

 the kaleidoscope, n ore especially concerning its discovery by Dr. Brewster, and 

 the circumstances in which it essentially differs from those instruments that have 

 been supposed to bear a general resemblance to it. The subject is so generally 

 interesting, that we do not hesitate to present to our readers a second and more 

 extended communication on the same topic, in which the history of the discovery is 

 more minutely traced, and the differences more fully detailed between the kalei- 

 doscope and the apparatus described by Bradley. We have omitted the letter 

 from Prof. Play fair to Dr. Brewster, as it had already appeared in the Annals, 

 retaining only the postcript; and we have also curtailed the article in some other 

 part*, which seemed of less importance. 



