the surface of a lens with the bare hands. The perspira- 

 ion is hard to remove. 



Objectives. If the front lens of an objective be- 

 comes soiled so that gently wiping will not clean it, 

 breathe upon it and then wipe gently with lens paper or 

 some soft linen. If this does not remove the soil, moisten 

 the paper with xylol or chloroform, being careful not to 

 use too much. Although the necessity of using these 

 reagents is unfortunate, it is better to use them and wipe 

 the lens gently than to apply too much friction. 



An immersion objective should always be cleaned 

 immediately after using. It can then be cleaned by 

 gen:ly wiping with a piece of lens paper. If the oil is 

 allowed to dry, xylol or chloroform must be used to 

 clean the lens. The oil collects dust and grit, which are 

 apt to scratch the lens. 



If any dust settles on the back lens of the objective 

 it is best removed by a earners hair brush. An eyepiece 

 should always be left in the tube to keep dust from 

 settling into the objective on the lower end. 



Never attempt to take an objective apart. If it has any 

 ailment serious enough for this it is serious enough to go 

 to the maker. 



Oculars. The oculars should be wiped as directed 

 for the objectives. Sometimes a grayish film forms on 

 the inner surfaces of the lenses. This necessitates re- 

 moving the lenses from the tube and wiping their surfaces. 



Condenser. What has been said of the eyepiece 

 applies to the condenser. The inner surfaces of the 

 lenses of the condenser should be cleaned if the condenser 

 is not clear after cleaning the outer surfaces. The objec- 

 tive cannot do its best work unless the condenser is clean. 



Mirror. The surfaces of the rr.irror demand the 

 same care and treatment as the lenses. 

 12 



