1 88 THE HISTOKV AND DEVELOPMENT OF THE MICROSCOPE 



.UK! from the front in tig. 151. This is brought round at one end 

 Mt right angles to the front, The fulcrum of this lever is at C, and 

 it fits under the pin I > \vhich is attached to a dovetailed piece, having 

 .it tin- back of it enclosed in a metal casing the counteracting spring 



FIG. l."o. FIG. 151. 



\VaW>n's sub-stage fine adjustment (1899). 



shown in fig. 151 ; when, therefore, the lever is depressed at B, the 

 sub-stage is raised at D and vice versa. The milled head A is placed 

 sit the side of the stage of the microscope towards the back slightly 



higher than the surface of the 

 stage. 



The fine sub-stage adjust- 

 ment of these makers as applied 

 to their ' Royal ' microscope is 

 shown as it is in its complete 

 form in fig. 152. 



Another sub-stage fine ad- 

 justment has been devised by 

 linker, which, we are of opinion, 

 it will be of advantage to the 

 student to understand. It em- 

 ploys tin- differential screw, and 

 JJBt'i by this means obtains a very 



i r,-. Sub-stu-.' line ncljustmrni com- sl(INV 11HA V1 ' "'' |j '-'"I"' student has 

 !'''' in Royal 1 microscope already understood that the prin- 



ciple of this screw is the cutting 



breads of a dim-rent - pitch/ one at either end of the screw, 

 the proportion of one to the other determining the amount of move- 

 breads found most Miitable for their sub sta-v fine ad- 

 justmenl were lo.-md 5n to the inch. In fiu. 15;; the screw AC 



