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



of the kaleidoscope, and that he has not even improved the 

 common catoptric cistula, which had been known long before. 

 The principle of inversion, and the positions of symmetry, were 

 entirely unknown to him. In the sixth scholium, he speaks of 

 rooms lined with looking-glasses, and of luminous amphitheatres, 

 which, as the Editor of the Literary Journal observes, have been 

 described and figured by all the old writers on optics.* 



The persons who have pretended to compare Dr. Brewster's 

 kaleidoscope with the combinations of plain mirrors described by 

 preceding authors, have not only been utterly unacquainted with 

 the principles of optics, but have not been at the trouble either 

 of understanding the principles on which the patent kaleido- 

 scope is constructed, or of examining the construction of the 

 instrument itself. Because it contains two plain mirrors, they 

 infer that it must be the same as eveiy other instrument that 

 contains two plain mirrors, and hence the same persons would, 

 by a similar process of reasoning, have concluded that a tele- 

 scope is a microscope, or that a pair of spectacles with a double 

 lens is the same as a telescope or a microscope, because all these 

 instruments contain two lenses. An astronomical telescope 

 differs from a compound microscope only in having the lenses 

 placed at different distances. The progress of the rays is exactly 

 the same in both these instruments, and the effect in both is 

 produced by the enlargement of the angle subtended by the 

 object. Yet surely there is no person so senseless as to deny 

 that he who first combined two lenses in such a manner as to 

 discover the mountains of the moon, the satellites of Jupiter and 

 Saturn, and all the wonders of the system of the universe, was 

 the author of an original invention. He who produces effects 

 which were never produced before, even by means which have, 

 been long known, is unquestionably an original inventor ; and 

 upon this principle alone can the telescope be considered as an 

 invention different from the microscope. In the case of the 

 kaleidoscope, the originality of the invention is far more striking. 

 Every person admits that effects are produced by Dr. Brewster's 

 instrument, of which no conception could have been previously 

 formed. 



All those who saw it, acknowledged that they had never seen 

 any thing resembling it before ; and those very persons who had 

 been possessors of Bradley's instrument, who had read Harris's 

 Optics, and who had used other combinations of plain mirrors, 

 never supposed for a moment, that the pleasure which they derived 

 from the kaleidoscope had any relation to the effects described 

 by these authors. 



No proof of the originality of the kaleidoscope could be 

 stronger than the sensation which it created in London and 



* The reader is requested to examine carefully the propositions in Harris's 

 Optics, which he will find reprinted in the Literary Journal, No. 10. He will 

 then he convinced that Harris placed both the eye and the object between the 

 mirrors, an arrangement which was known 100 years before his time. 



