236 THE HISTORY AND DEVELOP3IENT OF THE MICROSCOPE 



rack and pinion, while the fine adjustment is the now celebrated 

 lever employed liy this firm. One revolution of the milled head 



FIG. IMI. Widson's 'Fram ' microscope (1898). 



the :; , 1 1 ,,th of an inch. A.S we have seen (p. 170, 

 "U 11 -' 11 " 1 "' is sound in principle. ;md in practice all 



