380 On the Kaleidoscope. 



which Dr. Brewster has employed in his Kaleidoscope ; but tlic 

 means by wjiich the latter presents to tlie reflecting surfaces the 

 objects that are to be reflected, are quite different. Even uith 

 Bradley the kind of objects and the means bv which he presented 

 these objects to the mirrors were what constituted his instru- 

 ment a new invention ; for the arrangement of the reflectors 

 themselves was not of Bradley's discovering, as we shall prove 

 immedialelv. 



We copy the following from Jolm Baplhta Porto's Natural 

 Magic, the English Translation published in 1658, 



*' To make a plain Glass that shall represent the Image 

 munijuld. 



" A glass is made that will make many representations, that 

 is, that many things may be seen at once ; for bv opening and 

 shutting it, you shall see twenty fingers for one, and more. You 

 shall make it thus : Rai<e two brass looking-glasses [metallic 

 mirrors], or of crystal, at right angles upon the same basis, and 

 let them be in a proportion called sesquialtera, that is one and 

 a half, or some other proportion, and let them be joined together 

 longways, that they may le shut and opened, like a book; and 

 the angles be divers, such as are made at Venice : For one face 

 being oljjected you shall see many in them both, and this by so 

 much the straighter, as you put them together, and the angles 

 are less : but they will be diminished bv opening them, and the 

 angles being more obtuse, aou shall see the fewer: so showing 

 one figure, there will be more seen: and furlher, the right parts 

 will show right, and the left to be left, which is contrary to 

 looking-glasses ; and this is done by mutual reflection and pul- 

 sation, whence ariseth the variety of images interchangeable." 



From the foregoing it is manifest whence Bradley derived the 

 principle which he apj)lied to the construction of his instrument, 

 for he borrows the very words of Porta, " that they (the mir- 

 rors) may le shut a?id opened like a look;" and hence it follows 

 that if the discovery of the principle cannot be allowed to the 

 French, so neither can it to the English : for Porta's work was 

 first published (at Naj)les we believe) in 1.538, m faur looks, 

 and 35 years after (that is about the year 1573), in its enlarged 

 form, comprising tiventy looks. Bradley was not called a pla- 

 giarist, — probably bccai!;-e liis instrument, though identically the 

 same as Porta's, was applied in a different way and to a different 

 purpose. Should Dr. Brewster then be considered in that light, 

 for having made use of the same principle in his instrument, 

 which in construction is different from either Porta's or Brad- 

 lev's ? Porta, by looking at objects before him, along the angle 

 formed at tbejoini igof his glasses, saw them multiplied: Bradlev, 



by 



