68 THE MICROSCOPE. 



quently magnifying powers. When closed itwasi6 inches long and 

 gave 41 diam.; next length 90 diam.; 3d length iii diam., and 4th 

 143 diam. We find nothing to lead us to suppose Divini changed 

 his objectives. The amplifier, arrangement of lenses in eye-piece 

 and the construction allowing of change of eye-pieces as well as the 

 draw tubes, were all novelties. 



Same year (1660) Philip Bonnani produced and described two 

 microscopes. The more notable he described as having had three 

 glasses mounted in cylintlrical tube placed in horizontal position, 

 behind (below, if vertical) the stage was small tube with convex 

 lens at each end, beyond this was a lamp; the whole stand was 

 capable of various adjustments and regulated by rack and pinions. 

 The small tube was used as a substage condenser. The novelties 

 in this instrument were the motions by rack and pinion and the 

 condenser. 



Dr. Hooke produced, a few years later, a microscope in no way 

 superior to the foregoing, but being used by so prominent a man, 

 it certainly deserves mention and description. In the preface to 

 his Micrographia he speaks of it as an instrument 7 feet long, 5 

 diameters, 4 draws, 3 glasses, objective, amplifier, and ocular (deep). 



Hart.socker, in same period, 1674, long after Hooke's invention 

 of same, improved the single microscope by the use of small globules 

 of glass by means of which he made the discovery of spermatozoids. 

 I can find no statement of the size of his lenses. Priestley says 

 (Optics, p. 218), "were it not for the difficulty of applying objects 

 to these magnifyers, the want of light and the small field of distinct 

 vision, they certainly would have been the most perfect of all 

 microscopes." In other words, were it not for their imperfection 

 they would be quite perfect. 



Leuwenhoek, however, though not the most ingenious man in 

 this period, was certainly the most unremitting and successful 

 worker. Strange to say he never used a compound microscope, but 

 made all his discoveries during the many years of his life (died 

 aged 91) with the simple microscopes made entire with his own 

 hands. He rejected the compound as being unreliable owing to the 

 uncorrected aberrations. For each object or couple of objects he had 

 a microscope, so that according to his own statement he had hun- 

 dreds of instruments: " iVtihi quidem sunt centum centenque 

 microscopia." (L., vol. 2, p. 290.) Priestley incorrectly says 



