450 History ofllie Kaleidoscope. 



impunity by every person who chose to mannfacture Bradley's 

 instrument; but this was never tried*, and for the best of all 

 reasons, because nobody would have purchased it. 



We trust that no person, who wishes to judge of this subject 

 with candour, will form an opinion without having; actually seen 

 end used the instrument proposed by Bradley. Let any person 

 take Bradley's plates, and, having set them at an angle of 30'* 

 or 22i°, place them upon a cell containing fragments of coloured 

 glass, he will infallibly find that he cannot produce a picture of 

 any symmetry or beauty. The disunion of the sectors, the dark- 

 ness of the last reflections, and the enormous deviation from 

 symmetry, towards the centre of the figure, will convince him, 

 if he required conviction, that the instrument is entirely useless 

 as a kaleidoscope. To those, however, who are are not capable, 

 either for want of knowledge, or want of time, to make such a 

 comparison, we may present the opinion of three of the most 

 eminent natural philosophers of the present day, viz. the cele- 

 luated Mr. Watt, Professor Playfair, and Professor Pictet. 



" It has been said here," says Mr. Watt, " that you took the 

 idea of the kaleidoscope from an old book on gardening. Mv 

 friend the Rev. Mr. Corrie has procured me a sight of the book. 

 It is Bradley's Improvements of Planting and Gardening. Lon- 

 don 1731, part 2d, chap. 1st. It consists of two pieces of look- 

 ing-glass of equal bigness, of the figure of a long square, five 

 inches long and four inches high, hinged together, upon one of 

 the narrow sides, so as to open and shut like the leaves of a 

 book, which, being set upon their edges upon a drawing, will 

 show it iflultiplied by repeated reflections. This instrument I 

 have seen in my father's possession seventy years ago, and fre- 

 quently since, but what has become of it I know not. In mv 

 opinion, the application of the principle is very different from 

 that of your kaleidoscope." 



The following is Professor Playfair's opinion : 



" Edinburgh, May 1 1, 1818. 



" I have examined the kaleidoscope invented by Dr. Brewster, 

 and compared it with the description of an instrument which it 

 has been said to resemble, constructed by Bradley in 1717. I 

 have also compared its effect with an experiment to which it 

 may be thought to have some analogy, described by Mr. Wood 

 in his Optics, Prop. 13 and 14. 



* In illustration of this argument, wc may state the followinc; fact : Mr. 

 Carpenter of Birmingham, being anxious to evade Dr. Brewsttr's patent, 

 at a time when the manufacture of the patent kaleidoscope was in the hands 

 of another person, attempted to construct instruments in imitation of Brad- 

 ley's. After exercising his ingenuity for some time, he abandoned the at- 

 tempt as impracticable, and set off for Scotland for the purpose of offering 

 liis services in manufacturing the patent instrument. 



*' From 



