Care of Objectives and Eyepieces. Every 

 outfit should be provided with a camel's hair brush 

 and a well washed piece of linen. On account of its 

 fine texture chamois skin is desirable, but only after it 

 has been repeatedly washed. No dust should be per- 

 mitted to settle upon nor should the fingers come in 

 contact with any of the surfaces. Occasional cleaning 

 is desirable even when they (o and e p ) are not used, 

 as a film settles upon the outer as well as the inner 

 surfaces of the eyepiece and the rear surface of the 

 objective, and creates a cloudiness in the image. 



When not in use objectives and eyepieces should 

 be kept in their receptacles. If objectives are left 

 attached to the microscope either singly or on revolv- 

 ing nose-pieces, leave the eyepiece in the tube so that 

 no dust can enter and settle upon the rear lens of 

 the objective. 



Objectives especially should be kept where they 

 are not subject to extreme and sudden changes of 

 temperature as the expansion and contraction may 

 cause the cement between the lenses to crack. Also 

 avoid direct sunlight, as the cement may soften 

 sufficiently to ooze out. 



Eyepiece. Visible defects in the field are always 

 traceable to impurities in the eyepiece, not in the 

 objective, and are easily recognized by revolving it. 

 Indistinctness in the image or loss of light may be due 



