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Historic Microscopy. 



By E. M. Nelson. 



(Read Nov. 27th } 1885.) 

 During mv absence from town this summer I came across some 



'O 



quaint old descriptions of microscopes, which interested me so 

 much that 1 determined to make some notes of them, in the hope 

 that they might interest you also. My object in bringing this 

 paper before you is not to enter any debatable ground as to 

 whether A or B introduced a new principle or improvement with 

 regard to the microscope, but merely to trace the growth of human 

 intellect as expressed in the optical and mechanical parts of the 

 microscope, from the early simple type to the modern complex one. 



The earliest magnifying glass or simple microscope known is the 

 rock-crvstal biconvex lens in the British Museum. This was found 

 at Nineveh, and is probably not less than 2,500 years old. 



After a lapse of 22 centuries, we come to .the compound micro- 

 scope of Zacharias Jansen, in 1590. It consisted of two biconvex 

 lenses in a tube. The instrument was exceedingly rude, having no 

 stage, focussing, or illuminating apparatus. 



In 70 years we come to a great improvement by Hooke, who, in 

 1664, added a field glass to the eye-piece. This is practically the 

 compound microscope which is still in use, viz., eye-piece, formed 

 of fin eye glass and a field glass, and an objective. The instru- 

 ment was fitted with a very rough focussing apparatus, and an 

 illuminating lens formed of a globe filled with water, a method 

 still used by watch-makers and engravers. This microscope had no 

 stage. 



In 1668 Eustachio Divini invented a compound non-aplanatic 

 object glass. 



S. Campani, a contemporary of Divini and of Huyghens, used an 

 eye-piece which we now call Hnyghenian, but which the French 

 call after Campani. I believe, however, that there is no doubt 

 about its being the invention of Huyghens. 



