1818.] History of Dr> Bretvster's Kaleidoscope. 65 



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 1 have been a witness of lately in London. Not 

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

 grounded on a pretended similarity between your kaleidoscope 

 and Bradley's instrument, or such as Wood's or Harris's theories 

 might have suggested, appear to me to have any real foundation; 

 but I can affirm that neither in any of the French, German, or 

 Italian authors, who, to my knowledge, have treated of optics, 

 nor in Professor Charles's justly celebrated and most complete 

 collection of optical instruments at Paris, have I read or seen any 

 thing resembling your ingenious apparatus, which, from its 

 numberless applications, and the pleasure it affords, and will 

 continue to afford, to millions of beholders of its matchless 

 effects, may be ranked among the most happy inventions science 

 ever presented to the lovers of rational enjoyment. 



" M. A. PlCTET, 



Professor of Nat. Phil, in the 

 " To Dr. Brewster:' Academy of Geneva." 



The propositions in Harris's Optics relate, like Professor 

 Wood's, merely to the multiplication and circular arrangement 

 of the apertures or sectors formed by the inclined mirrors, and 

 to the progress of a ray of light reflected between two inclined 

 or parallel mirrors ; and no allusion whatever is made, in the 

 propositions themselves, to any instrument. In the proposition 

 respecting the multiplication of the sectors, the eye of the 

 observer is never once mentioned, and the proposition is true if 

 the eye has an infinite number of positions ; whereas, in the 

 kaleidoscope, the eye can only have one position. In the other 

 proposition (Prop. XVII.) respecting the progress of the rays, 

 the eye and the object are actually stated to be placed between 

 the reflectors ; and even if the eye had been placed without the 

 reflectors, as in the kaleidoscope, the position assigned it, at a 

 great distance from the angular point, is a demonstration that 

 Harris was entirely ignorant of the positions of symmetry either 

 for the object or the eye, and could not have comUnjd two 

 reflectors so as to form a kaleidoscope for producing beautiful or 

 symmetrical forms. The only practical part of Harris's proposi- 

 tions is the fifth and sixth scholia to Prop. XVII. In the fifth 

 scholium he proposes a sort of catoptric box or cistula, known 

 long before his time, composed of four mirrors, arranged in a 

 most unscientific manner, and containing opaque objects between 

 the speculmu. " Whatever they are," says he, when speaking 

 of the objects, " the upright figures between the speculum** 

 should be slender, and not too many in number, otherwise they 

 will too much obstruct the refected rays from coming to the eye." 

 This shows, in a most decisive manner, that Harris knew nothing 



Vol. XII. N° I. E 



