J. Coarse Adjustment, a mechanism for moving 

 the body quickly back and forth for adjusting the 

 focus approximately. It consists of a slide attached 

 to the body, and a straight rack, the former being 

 fitted to a recess, the latter engaging the teeth of a 

 pinion which is stationary in the arm. In instruments 

 of very simple form the coarse adjustment is obtained 

 by fitting the body in an outer stationary sheath. 



K. Milled-Heads, the large buttons attached 

 to the shanks of the pinion, which is revolved by 

 means of them. They are usually large to give 

 sensitiveness to the movement, and should be placed 

 wide apart so that the fingers may be entirely free 

 from the body. 



L. Micrometer Screw, a fine screw provided 

 with milled head. It acts upon the body either 

 directly or by levers. It has a slow and delicate 

 movement and provides the fine adjustment. This as 

 well as the coarse adjustment should be extremely 

 sensitive and should not have the least side or lateral 

 motion. The fact that either of them has it, is 

 evidence of poor workmanship. 



M. Stage, consists of a strong metal plate, placed 

 at a right angle to the body, and provided with an 

 opening for the passage of light iiom below. The 

 object is placed upon it for examination. 



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