336 



THE AMERICAN MONTHLY 



[Nov 



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

 proper position, t, as a secondary condensing- lens was 

 littod to a double-jointed arm. The illuniinating- ajipar- 

 atus was therefore suitable for opa(j[ue objects, and must 

 be regarded as being very complete and edicieiit in its 

 day. 



Fig. 4 shows Divini's microscope (1067). Tin' interest 

 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 s[)herical aberration. 



Fig. 5 exhibits an improvement on the preceding form, 

 by Cherubin d'Orleans (1671). The body was more ) ig- 

 idly mounted by the enlargement of the tri])od foot. A 

 screw movement was fitted to the stage for foi iissiii<i. 

 Tn the optical ]).'irt there is an erector. Cheniliiii 

 d'Orleans was the Urst to ap])ly an erectoi" to his monoc- 

 ular microscope, an<l lie was also ihc first to constiuct a 

 binocular microscoi)*-. The l)inoculai- insti uiniMit woiihl, 

 according to the drawing, have <rivrn a jiseudostcico- 

 scopic image. 



