secure the pin and put it in place. This ought to be 

 done by the maker or an experienced mechanic. 



In some cases, especially in microscopes (continental 

 type) where the prism is used in the fine adjustment the 

 lubricant in the prism becomes gummed so that the 

 adjustment fails to respond promptly, and then jumps. 

 The bearings should be thoroughly cleaned and oiled 

 with paraffin oil or watch oil. This ought to be done 

 by the manufacturers because the mechanism is so 

 delicate that even though safely taken apart, it would 

 be put together and adjusted with great difficulty. 



Draw Tube. The draw tube should work easily 

 and smoothly. With those which are nickeled and 

 sliding in a cloth lined sleeve, little trouble will be found. 

 Where they are not nickeled, care must be given them 

 similar to that described for the sliding tube coarse 

 adjustment. In pushing in the draw tube be careful not 

 to push down the body tube and thereby run the front 

 of the objective into the cover glass. 



Substage. The rules given above apply to the parts 

 of the substage in general. The threads on the quick 

 acting screw on the instruments so provided are apt to 

 become gummed, making it hard to focus the condenser. 

 This gum is easily "cut" with xylol or chloroform, per- 

 mitting the screw to work easily. 



If the leaves of the iris diaphragms become rusted or 

 gummed, clean them with xylol, and oil them thoroughly 

 by opening and closing the diaphragm several times to 

 evenly distribute the oil over the leaves. Should the 

 leaves become bent or misplaced, submit them to the 

 maker or a skilled workman. 



IMoseplece. When bought at the same time the 

 nosepieces and objectives of all the best makers are now 

 10 



