KALEIDOSCOPE. 



*411 



i Brailley ever thought of applying iiis mirrors; 

 yet the kaleidoscope is in every respect a superior in- 

 ' ~tniment, even for that inferior purjxise, and gives true 

 symmetrical farms, which the odier instrument is in- 

 capable of doing. 



In the comparison which has now been made, we 



have degraded the kaleidoscope, by contracting it- ef- 



those which Bradley's instrument is capable 



r t!iese effects are not worth the looking 



at. When we attempt to employ Bradley 's instrument 



duce the effects which liave been so much admir- 

 ed in the kaleidoscope, namely, to produce beautiful 

 forms from transparent or opaque coloured objects con- 

 tained in a cell, and at the end of the reflectors, it fails 

 to entireK . that ni> person has succeeded in the attempt. 

 It i- indeed quite impossible to produce by it the beau- 

 tiful and symmetrical forms which the kaleidoscope dis- 

 play*. Had this been possible, Dr. Brewster's patent 

 might have been invaded with impunity by every per- 

 son who chose to manufacture Bradley'* instrument ; 

 but this was never tried, and for th* best of all reasons, 

 because nobody wduld have purchased it. 



\\ '< trust that no person, who wishes to judge of this 

 snhjtft with candour, will form an opinion without ha- 

 ving actually teen and uied the instrument proposed by 

 Bradley. Let any person take Bradley's plates, and, 

 having set them at an angle of SO 1 or 8*4, place them 

 upon a cell containing fragments of coloured glass, he 

 will infallibly rind that he cannot produce a picture of 

 any yntmrtry or beauty. The disunion of the sectors, 

 the darkaess of the last reflections, and the enormous 

 deviation from symmetry, towards the centre of the 

 figure, will run', ir.. i he required conviction, 



that the instrument is entirely useless as a kaleidoscope. 



<*e, however, who are nut capable, either for want 

 of knowledge, or want of time, to make such a compa- 

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

 eminent natural philosophers of the present dav 

 the celebrated Mr. \\ ,tt. Professor Playfair, and Pro- 

 CMBOT Pictet. 



has been said here," says Mr. Watt, thnt 

 took the idea of the kaleidoscope from an old book on 

 gardening. M> friend, the Rev. Mr. C'orrie, has pro- 

 cured me a sight of the U>k. It is Bradley's luiprmc- 

 of Planting and Gardening. London 1731, part 

 2d. chap. 1st. It consists of two pieces of looking glass 

 of equal bigness, of the figure of a long square, ti\ c 

 inches long and four inche. high, hinged together. >i|K.n 

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

 Ismvss of a book, which, being set upon their edges 

 upon a drawing, will shew it multiplied by repeated 

 reflection*. This instrument I have seen in my father's 

 possession 70 years ago, and frequently since, but what 

 has become of it I know- not. In my opinion, the ap- 

 plication of the principle is very different from that of 



..H ir k.-ileid.-4-ope." 



The following is Professor Pla yfair's opinion : 



I 



Edinburgh, ll/A May, 1818. 

 cammed the kaleidoscope invented In Dr. 

 r, and compared it with tlu .!.--< r.prmi of an 

 which it has been said to resemble, con- 

 I by Bradley in 1717. I have also com jured it* 

 with an experiment to which it may be thought 

 to have smne analogy, described by Mr. W.M| m |,j, 

 plies. Prop. 15 and 1 V 



- rom Ixith thee contrivances, and from every op- 

 tical instrument with which I am acquainted, the ka- 

 leidoscope appears to differ essentially both in its i 

 and in the principles of its maaUaiiUuii 



" As to the effect, the thing produced by the kalei- Kaleido- 

 doscope is a series of figures presented with the most ^ scope. 

 perfect symmetry, so as always to compose a wliole, in """V"^ 

 which nothing is wanting anil nothing redundant. It 

 matters not what the object be to which the instrument 

 is directed, if it only be in its proper place, the effect 

 ju-t ilescrilKtl is sure to take place, and with an endless 

 variety. In this respect, the kaleidoscope appears to 

 l>e quite singular among optical instruments. Neither 

 the instrument of Bradley, nor the experiment or theo- 

 rem in Wood's book, have any resemblance to this ; 

 they go no further than the multiplication of the 

 figure. 



" Next, as to the principle of construction, Dr. Brew- 

 ster's instrument requires a particular position of the 

 eye of the observer, and of the object looked at, in 'order 

 to its effect. If either of these is wanting, the symme- 



a vanishes, and the figures are irregular and disunit- 

 In the other two cases, no particular position, ei- 

 ther for the eye or the object, is required. 



" For these reasons, Dr. Brewster's invention seems 

 to me quite unlike the other two. Indeed, as far as I 

 know, it is quite singular among optical instruments ; 

 and it will bejiiattcr of sincere regret, if any imagina- 

 ry or vague analogy, between it and other optical in- 

 struments, should l>e the means of depriving the Doc- 

 tor of any part of the reward to which his skill, inge- 

 nuity, and perseverance, entitle him so well. 



JOHN PLAY FAIR, 



Profettor of Natural Philosophy in the 

 ''rtity of Edinburgh. 



" P. S. Granting that there were a resemblance be- 

 tween the kaleidoscope and Bradley 's instrument, in 

 any of the particulars mentioned above, the introduc- 

 tion of coloured and moveable objects, at the end of die 

 reflectors, b quite peculiar to Dr Hrcw-tcr's instrument. 



. ing of atten- 

 tion, is the u -< of two li n-c* .ind a draw tul>e. so that 

 tion of the kjjcidoscopc i* extended to objects of 

 all size*, and at all < I rom the observer, and 



united, by that mean*, to the advantages of the tele- 

 scope. J. P." 



Professor Pictet's opinion is stated in the following 



letter : 



Among \our friends, I have not been one of 

 the lc.i-t p-iinfully affected by the -liameful invasion of 

 your rights as an inventor, which I have been a witness 



y in London. Not only none of the allegations 

 of the invaders of your patent, grounded on a pretend- 

 ed similarity lirtw rrn your kaleidoscope and Bradley's 

 instrument, or such as Wood's or Harris 1 theories might 

 have s .i|i|i'ar to me to have any real founda- 



tion ; but, I can affirm that, neither in any of the 

 French, dermaii, or Italian authors, who, to my know- 

 ledge, have treated of optics, nor in Professor Charles' 



celebrated and most complete collection of opti- 

 cal instrument* at Paris, have 1 read or seen any thing 

 resembling your ingenious apparatus, which, from its 

 iiumlicrless applications, and the pleasure" it affords, and 

 will continue to afford, to millions of beholders of its 

 matchless effect*, m.iy b<- ranked among the most hap- 

 py inventions science ever presented to the lovers of 

 rational enjoy inent. 



M. A. PICTET, 

 Proft'unr of Mat. Phil in the 



Academy of Geneva. 

 To Dr. Brtivtter. 



