352 E, M. NELSON ON THE EVOLUTION OF THE MICROSCOPE. 



by a link and butterfly nut, q ; obviously, therefore, the object 

 can be placed in any desired position by these combined move- 

 ments. 



The lamp also was attached to a separate upright support by 

 a ring and screw nut, very much in the same way as it is fixed 

 at the present time. There was an engraver's 

 globe, n, filled with water for a primary condensing 

 bull's eye, and a plano-convex lens, turned in its 

 proper position, f, as a secondary condensing lens 

 was fitted to a double-jointed arm. The illu- 

 minating apparatus was therefore suitable for 

 opaque objects, and must be regarded as being 

 very complete and efficient in its day. 



Fig. 4 shows Divini's microscope (1667). The in- 

 terest in this instrument is not in the mount, which 

 is of the crudest form, but in the optical part, for 

 in place of the biconvex eye lens two plano-convex 

 lenses, with their convex surfaces in contact, were 

 used. This plan would halve the amount of the 

 spherical aberration. 

 Fig. 5 exhibits an improvement on 

 the preceding form, by Cherubin 

 d'Orleans (1671). The body was 

 more rigidly mounted by the en- 

 largement of the tripod foot. A 

 screw movement was fitted to the 

 stage for focussing. In the optical 

 part there is an erector. Cherubin 

 d'Orleans was the first to apply an 

 erector to his monocular microscope, 

 and he was also the first to construct 

 a binocular microscope. The bino- 

 cular instrument would, according 

 to the drawing, have given a pseudo- 

 stereoscopic image. 



In 1672 Sir Isaac Newton suggested 

 a reflecting microscope of the form of a Herschelian telescope. 

 It probably was never made. 



Leeuwenhoek's microscopes, constructed in 1673, are remark- 

 able more on account of the man who used them than for their 



Fig. 4. 



Fig. 5. 



