to soiled or coated surfaces in either eyepiece or 

 objective. 



Dust if on either the eye-lens or field-lens is apparent 

 as dark, indistinct spots. 



To dean the surfaces, breath upon them and, 

 giving a revolving motion to the eyepiece, wipe with 

 well washed linen and finally blow upon the surface, or 

 use camel's hair brush to remove particles of lint. 



At regular periods unscrew the eye-lens and field- 

 lens and clean the inner surfaces. 



Objective. This should be used with the utmost 

 care. The systems should never be separated, even if 

 they can be unscrewed, as they are liable to become 

 decentered and dust may enter. 



Avoid all violent contact of the front lens with the 

 cover glass. The oil immersion objectives are partic- 

 ularly sensitive and easily ruined. 



Screw into the nose-piece and unscrew by grasping 

 the, knurled edge and keeping in line with the tube. 



Occasionally examine the rear surface of the objec- 

 tive with magnifier and if dust be present remove with 

 camel's hair brush. 



Clean an immersion objective immediately after it 

 has been used by removing the fluid with moist cloth 

 and wiping clean with dry cloth or lens paper. 



While cleaning give the objective a revolving motion. 



201 



