120 THE HISTORY AND DEVELOPMENT OF THE MICROSCOPE 



probable (but by no means certain) that Hans and Zacharias Jaiisson. 

 spectacle makers, of Middelburg, Holland, were the inventors. But 

 it would appear that the earliest microscope was constructed for 

 observing objects by reflected light only. 



At the Loan Collection of Scientific Instruments in London in 

 1876 an old microscope, which had been found at Middelburg, was 

 shown, which, Professor Harting considered, might possibly have 

 been made by the Janssens. It is drawn in fig. 90, and consists of 

 a combination of a convex object-lens and a convex eye- 

 lens, which form was not published as an actual con- 

 struction until 1646 by Fontana, which, as Mr. Mayall 

 points out, does not harmonise with the assumption 

 that this instrument was constructed by one of the 

 Janssens. 



It is strictly a compound microscope, and the dis- 

 tance between the lenses can be regulated by two 

 draw-tubes. There are three diaphragms, and the eye- 

 lens lies in a wood cell, and is held there by a wire ring 

 sprung in. The object-lens, a, is loose in the actual 

 instrument, but was originally fixed in a similar way 

 to b. 



It cannot be an easy task if it be even a pos- 

 ' sible one to definitely determine upon the actual indi- 

 JanssenV vidual or individuals by whom the compound micro- 

 compound scope was first invented. Recently some valuable 

 evidence has been adduced claiming its sole invention 

 for Galileo. In a memoir published in 1888 l Professor 

 G. Govi, who has made the question a subject of large and continuous 

 research, certainly adduces evidence of a kind not easily waived. 



Huyghens and, following him, many others assign the invention 

 of the compound microscope to Cornelius Drebbel, a Dutchman, in 

 the year 1621 ; but it has been suggested that he derived his know- 

 ledge from Zacharias Janssen or his father, Hans Janssen, spectacle 

 makers, in Holland about the year 1590; while Fontana, a Nea- 

 politan, claimed the discovery for himself in 1618. It is said that 

 the Janssens presented the first microscope to Charles Albert, Arch- 

 duke of Austria ; and Sir D. Brewster states, in his * Treatise on the 

 Microscope,' that one of their microscopes which they presented to 

 Prince Maurice was in 1617 in the possession of Cornelius Drebbel, 

 then mathematician to the Court of James I., where 'he made 

 microscopes and passed them off as his own invention.' 



Nevertheless we are told by Viviani, an Italian mathematician, 

 in his ' Life of Galileo,' that ' this great man was led to the discovery 

 of the microscope from that of the telescope,' and that 'in 1612 he 

 sent one to Sigismund, King of Poland.' 



We now receive evidence through the researches of Govi that 

 the invention was solely due to Galileo in the year 1610. Professor 

 Govi understands by ' simple microscope ' an instrument ' consisting 

 of a single lens or mirror,' and by ' compound microscope ' one ' con- 



1 Atti R. Acad. Sci. Fis. Nat. Napoli, vol. ii. series ii. ' II microscopic composto 

 inventato da Galileo,' Journ. R.M.S. Pt. IV. 1889, p. 574. 



