132 THE HISTOEY AND DEVELOPMENT OF THE MICROSCOPE 



In 1672 Sir Isaac Newton communicated to the Royal Society 

 a note and diagram for a reflecting microscope ; we have, however, 

 no evidence that it was ever constructed. But in 1673 Leemven 

 hoek began to send to the Royal Society his microscopical discoveries 

 Nothing was known of the construction of his instruments, except 

 that they were simple microscopes, even down to so late a period as 

 1709. We know, however, that his microscopes were mechanically 

 rough, and that optically they consisted of simple bi-convex lenses, 

 with worked surfaces mounted between two plates of thin metal 

 with minute apertures through which the objects were directly seen. 

 At his death Leeuwenhoek bequeathed a cabinet of twenty-six of his 

 microscopes to the Royal Society ; unhappily, they have mysteriously 



_^^ disappeared. But Mr. May 



ISjjV all was enabled to figure one 

 """''* lodged in the museum of the 

 Utrecht University, which i> 

 given in figs. 99 and KM) in 

 full size. The lens is seen in 

 the upper third of the plate. 

 It has a J-inch focus. The 

 object is held in front of the 

 lens, on the point of a short 

 rod, with screw arrange- 

 ments for adjusting the 

 object under the lens. 



Many modifications of 

 this and the preceding in- 

 struments are found with 

 some early English forms, 

 but no important construc- 

 tive or optical modification 

 immediately presents itself. 

 But some ingenious arrange- 

 ments are found in the 

 simple microscopes de v i s d 

 by Musschenbroek in the 

 early years of the eighteenth 

 century. 



Grindl figured a microscope in hip ' Micrographia Nova ' in 

 1687, in which optical modifications arise. Divini had, as was 

 stated, combined two plano-convex lenses, with their convex surfaces 

 facing, to form an eye-piece : this idea was carried further in 1 668 

 by a London optician, who used two pairs of these lenses ; Grindl 

 did this also, but in addition he used two similar (but smaller) lenses 

 in the same manner as an objective. The form of the microscope 

 itself was copied from that of Cherubiii d'Orleans (fig. 97), but was 

 modified by the application of an external screw. 



In 1691 Bonannus modified preceding arrangements by devising 

 a means of clipping the object between two plates pressed away from 

 the object-lens by a spiral spring, the focussing being then effected 

 by a ' screw-barrel.' 



FIG. 99. FIG. 100. 



Leeuwenhoek's microscope (1C>7:1 . 



