E. M. NELSON ON EVOLUTION OF THE MICROSCOPE. 



105 



in an English microscope. The mirror is concave. The very 

 inappropriate name " reflecting " given to this microscope was 

 owing to the iUuminating mirror ; it was essentially a dioptric and 

 not a catoptric instrument. Dr. Smith, in his account of it, 

 suppresses the word " reflecting." 



As Fig, 16 explains itself, it -will only be necessary to notice a 



Fig. 16. 



few minor points : first the unscrewing of the objective on the 

 nose piece was used as a fine adjustment, the coarse adjustment 

 being performed by placing the sliding tube to a mark. The 

 three brass pillars constituting a non-inclinable rigid tripod were 

 an improvement on the Divini and Cherubin d'Orleans. This 

 microscope is by Baker in 1742 called an improvement of J. 

 Marshall's, but this is surely a mistake, as they have nothing in 

 common except the octagonal box foot. 



