History of the Kalridnscopp. 453 



glasses, and of luminous amphitheatres, which, as the Editor of 

 the Literary Journal oliservcs, have been described and figured 

 by all the o\<i writers on optics*. 



Tlie per'^vins who have pretended to compare Dr. Brewster's 

 kaleiil )'seope with the combinations of plain mirrors described by 

 preceding; autli'M-s, have not only been utterly unacquainted with 

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

 of understanding the principles on wliich the patent kaleidoscope 

 is constructed, or cf examining the construction of the in^'irument 

 itself. Because it contains two plain mirrors, they infer that it 

 must be the same as every other instrument that contains two 

 plain mirrors ; and herre the same persons would, by a similar 

 process of reasoinnsf, have concluded that a telescope is a micro- 

 scope, or that a pair of spectacles with a double lens is the same 

 as a telescope or a microscope, because all these instrumenla 

 contain l-vo lenses. An astronomical telescope differs from a com- 

 pound microscope only in having the lenses placed at different 

 <listances. Tlj€ progress of the rays is exactly the same in both 

 these instiument?, and the effect in both is produced bv the en- 

 largement of the angle sul)tended by the oiyect. Yet surely 

 there is no p.'rson so senseless as to deny that he who first com- 

 bined two lenses in such a manner as to discover the mountains 

 of the moon, the satellites of Jupiter and Saturn, and all the 

 'vonders of the system of the universe, was the author of an ori- 

 ginal invention. He who produces effects which were never pro- 

 duced before, even by means which have been long; known, is 

 unquestionably an original inver.tor ; and upon this princij>l3 

 alone can the telescope be considered as an invention different 

 from the microscope. In the case of the kaleidoscope, the ori- 

 ginalitv of the invention is far more striking. Every person ad- 

 mits chat effects are produced by Dr. Brewster's instnmient, of 

 which no conception could have been |)reviously formed. 



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

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

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

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

 never supposed for a moment, that the pleasure v,-hic!i thev de- 

 rived from the kaleidoscope had any relation to the effects de- 

 bcribed bv these authors. 



No proof of the originality ofthe kaleidoscope could be stronger 



• Th? reader is requested to examine carefully the propositions in liar-, 

 ris's Opticks, wT.ich he will find reprinted in the Literary Journal, No. I'>, 

 He will then be roiivinced, that Harris placed both the eye and the object 

 bef.vren the mirror?, an arranj^'cment which '.vas known 100 years befoi-e 

 his t)i»j<?, ■ . 



rn than 



