and at one end the screw comes to a stop and at 

 the other goes beyond the limit of movement and 

 becomes inoperative. It should always be kept as 

 near as possible at the medium point of its range. 

 Grasp the milled head of the fine adjustment between 

 the thumb and forefinger of one hand (right) turning 

 the screw in either direction to focus in different planes 

 of the object, while the other hand (left) moves the 

 object. 



" In the manipulation of the microscope it is not 

 uncommon to observe the operator rolling the milled 

 head of theflne adjustment instead of firmly grasping 

 it between the finger and thumb and governing, to the 

 minutest fraction of arc, the amount of alteration he 

 desires. It is undesirable and an entirely inexpert 

 procedure to roll the milled head, and cannot yield the 

 fine results which a delicate mastery of this part of the 

 instrument necessitates and implies. To use aright 

 the fine adjustment of a first-class microscope is not 

 the first and easiest thing mastered by the tyro. We 

 have already intimated that the fine adjustment should 

 never be resorted to while the coarse adjustment can 

 be efficiently employed. The focus should always be 

 found, even with the highest powers, by means of the 

 coarse adjustment." (Carpenter, The Microscope and 

 its Revelations.) 



Use of Substage Diaphragm. The intelligent 

 use of the diaphragm is a great aid to good results, 



129 



