KALEIDOSCOPE. 



of tin; instrument being thus made public, the tinmen 

 and glaziers began to manufacture the detached parts 

 of it, in order to evade the (latent ; while others manu- 

 red and sold the instrument complete, without 

 being aware that the exclusive property of it had been 

 M cured by a p:'tent. 



In this way the invasion of the patent right became 

 general amongthat class of individuals against whom the 

 law is seldom enforced but in its terrors. Some workmen 

 of a higher class were encouraged to piracy by this uni- 

 versal opposition to the patent; but none of the respec- 

 table London opticians would yield to the clamours of 

 their customers, to encroach upon the rights of an in- 

 ventor, to whom they were at least indebted for a new 

 and a lucrative article of trade. 



In order to justify these piratical proceedings, it be- 

 came necessary to search for some combinations of plain 

 mirrors, which might be supposed t6 have a resem- 

 blance to Dr. Brewster's instrument ; and it would 

 have been strange, indeed, if some theorem or experi- 

 ment had not been discovered, which could have been 

 used to impose upon the great crowd who are entirely 

 ignorant of the principles and construction of optical 

 instruments. There never was a popular invention, 

 which the labours of envious individuals did not at- 

 tempt to trace to some remote period ; and, in the pre- 

 sent case, so many persons had hazarded their fortunes 

 and their characters, that it became necessary to lay 

 hold of something which could be construed into an 

 anticipation of the kaleidoscope. 



The first supposed anticipation of the kaleidoscope 

 was found in Prop. XIII. and XIV. of Professor Wood's 

 Optics, where that learned author gives a mathematical 

 investigation of the number and arrangement of the 

 images formed by two reflectors, either inclined or pa- 

 rallel to each other. These theorems assign no posi- 

 tion, either to the eye or to the object, and do not even 

 include the principle of inversion, which is absolutely 

 necessary to the production of symmetrical forms. The 

 theorems, indeed, are true, whatever be the position of 

 the object or of the eye. In order to put this matter 

 to rest, Dr. Brewster wrote a letter to Professor Wood, 

 requesting him to say if he had any idea of the effects 



of the kaleidoscope when he wrote these 



propo: 



isitions. 



To this letter, Dr. Brewster received the following 

 handsome and satisfactory answer : 



Si. Johns, May \$th, 1818. 



" Siu, The propositions 1 have given relating to 

 the number of images formed by plane reflectors inclin- 

 ed to each other, contain merely the mathematical cal- 

 culation of their number and arrangement. The effects 

 produced by Ike kaleidoscope n-ere never in my con empla- 

 tioii. My attention has for some years been turned to 

 other subjects, and 1 regret that I have not time to read 

 your Optical treatise, which I am sure would give me 

 great pleasure. I am, Sir, your most obedient humble 

 servant, 



" J. WOOD." 



The next supposed anticipation of the Kaleidoscope 

 was an instrument proposed by Mr. Bradley in 171?. 

 1 his instrument consists of two large pieces of silvered 

 Jooking-gluss. ii vc inches ivide, and four inches high, 

 jointed together with hinges, and opening like a book. 

 I hese plates being set upon a geometrical drawing, and 

 the eye being placed i n front of the mirrors, the lines 

 of the drawing were seen multiplied by repeated reflec- 

 tions This instrument was described long before by 



6 



Kircher, and did not receive a single improvement from 

 the hands of Bradley. It lias been often made by the 

 opticians, and was principally used for multiplying the 

 human face, when placet! between the imVrors ; but no 

 person ever thought of applying it to any purpose of 

 utility, or of using it as an instrument of rational amuse- 

 ment, by the creation of beautiful form*. From the 

 very construction of the instrument, indeed, it is quite 

 incapable of producing any of the singular effects exhi- 

 bited by the kaleidoscope. It gives, indeed a series of 

 reflected images arranged round a centre ; but so does 

 a pair of looking-glasses placed angularly in an apart- 

 ment, and so do the pieces of mirror glass with which 

 jewellers multiply the wares exhibited at theii; windows. 

 It might therefore be as gravely maintained that uny 

 of these combinations of mirrors was a kaleidoscope, as 

 that Bradley's pair of plates was an anticipation of that 

 instrument. As the similarity between the two has been 

 maintained by ignorant and interested individuals, we 

 shall be at some pains to explain to the reader the dif- 

 ferences between these two instruments ; and we shall 

 do this, first, upon the supposition that the two instru- 

 ments are applied to geometric lines upon paper. 



Kaleido. 

 scope. 



1. In Bradley's instru- 

 ment, the length is less 

 than the breadth of the 

 plates. 



2. Bradley's instrument 

 cannot be used with a 

 tube. 



3. In Bradley's instru- 

 ment, from the erroneous 

 position of the eye, there 

 is a great inequality of 

 light in the sectors, and 

 the last sectors are scarcely 

 visible. 



4. In Bradley's instru- 

 ment, the figure consists 

 of elliptical, and conse- 

 quently unequal sectors. 



5. In Bradley's instru- 

 ment, the unequal sectors 

 do nut unite, but are all se- 

 parated from one another 

 by a space equal to the 

 thickness of the mirror 

 glass. 



6. In Bradley's instru- 

 ment, the images reflected 

 from the first surface in- 

 terfere with those reflected 

 from the second, and pro- 

 duce a confusion and over- 

 lapping of images entirely 

 inconsistent with symme- 

 try. 



7. In Bradley's instru- 

 ment, the defects in the 

 junction of the plates are 

 all rendered visible by the 

 erroneous position of the 

 eye. 



1. In the kaleidoscope, 

 the length of the plates 

 must be four, or five, or 

 six times their breadth. 



2. The kaleidoscope 

 cannot be used without a 

 tube. 



3. In the kaleidoscope, 

 the eye is placed, so that 

 the uniformity of light is 

 a maximum, and the last 

 sectors are distinctly visi- 

 ble. 



4. In the kaleidoscope, 

 all the sectors are equal, 

 and compose a perfect cir- 

 cle, and the picture is per- 

 fectly symmetrical. 



5- In the kaleidoscope, 

 the equal sectors all unite 

 into a complete and per- 

 fectly symmetrical figure. 



6. In the kaleidoscope, 

 the secondary reflections 

 are entirely removed, and 

 therefore no confusion 

 takes place, 



7- In the kaleidoscope, 

 the eye is placed so that 

 these defects of junction 

 are invisible. 



The reader will observe, that in this comparison the 

 two instruments are supposed to be applied to geometric 

 lines iii>o>i paper, and that this was the only purpose to 



