334 THE AMERICAN MONTHLY [Nov 



inHaciu-ed the design of Powell's No. 1. We suy i>ro- 

 bably, be<-ause it is possible that Poweirs No. I, or any 

 other form of microscope or apparatus, might have been 

 designed by an inventor wholly unacquainted with any 

 preceding form, thongh in the absence of any evidence to 

 the contrary such a liyi)othesis would be highly improb- 

 able. 



Those parts of this paper w^hicii treat of old micro- 

 scopes are not intended to be a history of the micro- 

 scopes; many iuteresting old forms will not even be 

 mentioned. For the most part attention will be drawn 

 to only those instruments that have been rungs in the 

 ladder of evolution. 



To begin, then, neither the name of the iuventi>r nor 

 the date of the first compound microscope has been 

 with certainty determined. There is an extensive litera- 

 ture on the subject, and the conclusion arrived at is that 

 the first n)icroscope was probably made by Jansen, a 

 spectacle maker, of Middelburg, in Holland, about the 

 year 1660. An old microscope, supposed to be a Jansen, 

 was exhibited at the loan collection of scientific instru- 

 ments at South Kensington in 1876 (catalogue No. 3.510), 

 the date of it given in the catalogue being 1590. This 

 instrument had neither stand, object-holder, nor stage; 

 the only mechanical movement with which it was fur- 

 nished was a draw tube for separating the two con\ex 

 lenses which formed tlie optical part of the instrumrnt 



(Fig. 1). 



The next step is to be found in ;i drawing of a .-iniplc' 

 microscope by Descartes in his "Dioptrique" in 1637. 

 This shows a jdano convex lens j)lact'd at the vertex of a 

 concave mirror: in short it is an instruu)ent now known ;i> 

 a Lieberkuhn. It is curious to note that while Descarics 

 is very particular about the ]»arabi)li(' curves of his mii'- 

 rors and the hyperbolic curves of his lenses the figun^s 

 show the lenses turned the wrong way, which would 



