802 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



upper surface of tlie condenser to mark the centre. The focus of the 

 condenser is adjusted by rack-and-pinion movement. 



The principal novelty, however, is in the application of a lever to the 

 parallel-spring fine- adjustment of Bausch and Lomb, by which Messrs. Swift 

 have greatly lessened the speed of the movement, at the same time reversing 

 the action of the focusing screw.* 



Stephenson's Erecting Binocular Microscope. — Mr. J. W. Stephenson's 

 Erecting Binocular Microscope has approved itself to microscopists, and 



Fig. 209. 



especially to botanists, as by far the most practical and convenient form 

 hitherto devised where high powers are to be used. Indeed, with the 



* See infra, p. 808. 



