is very seldom any occasion for this, however, if used 

 with reasonable care. 



If the fine adjustment does not respond to the 

 turning of the micrometer screw, or if it comes to a 

 stop, it indicates that the adjustment screw has come 

 to the limit of its motion at either end. It should by 

 no means be forced ; it should at all times be kept at 

 a medium point. 



The micrometer screw should never be removed 

 unless after long use it works with a pronounced gritty 

 feeling. In this case unscrew from its bearing, wipe 

 clean with a cloth moistened with benzole, and after 

 wiping dry apply good tallow, being careful to start the 

 threads properly. If they are not properly started 

 much mischief may be done. In some instruments the 

 threads are left handed. In removing the screw 

 observe whether there is a small steel pin in a recess 

 in it, and if so be careful that this is in proper position 

 when returned or else the fine adjustment will be 

 inoperative. 



Screw- Driver. Ordinary screw-drivers are not fit 

 for use on the microscope. A properly made screw- 

 driver should be ground on its two large surfaces so 

 that they are parallel and not wedge shaped, so that it 

 will exactly fit in the slot of the screw head. In using, 

 turn the screw with a slow, steady motion, pressing the 

 screw-driver slowly into the slot. No screw head will 

 ever be injured or marred if these points are observed. 



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