22 



must be sufficient to retain the slide firmly in posi- 

 tion. This causes a certain amount of friction 

 between the lower surface of the slide and the upper 

 one of the stage, which at times is very annoying, in 

 that it is difficult to move the object to a point 

 desired, with certainty. The motion is "jerky" and 

 disagreeably harsh unless the stage is very clean. 



A large number of plans have been devised to 

 overcome this difficulty, which have proven very 

 efficient. They may be termed semi-mechanical, in 

 that the fingers do not come in direct contact with 

 the slide. Usually glass is brought in contact with 

 the metal, but so arranged as to offer as few and 

 small points of contact as possible. 



Fig. 7. 



In Fig. 7 we show a so-called glass-stage and slide- 

 carrier, in which the stage is merely for the support 

 of the slide-carrier. This latter is arranged to 

 receive the slide and rests upon the glass by small 

 points. At its ends are two projecting tongues 

 which are bent downward and inward and act as 

 springs against the lower surface of the glass plate. 

 While the movements must be carried out by the 

 hands, they are smooth and steady and work with 

 ease, even under high powers. 



