34 PRACTICAL MICROSCOPY. 



the varnish around the edge of the cover will stiffen, and eventually 

 become solid. Do not paint colored rings around the specimen. 

 Nothing can present a neater appearance than the simple mount, as I 

 have described it, after having been properly labelled. Labels 

 seven-eighths of an inch square may be put on one or both ends, with 

 the name of the object, date, method of staining, or whatever par- 

 ticulars you may prefer. 



Specimens should be kept in trays or boxes so as to always lie 

 flat. 



CARE OP THE MICROSCOPE. 



The objectives constitute the most valuable part of the instrument. 

 The lenses should never be touched with the fingers; indeed the same 

 rule applies to all optical surfaces. When the glasses become soiled, 

 they may ce cleaned, but it should be done with great care. While 

 the effect of a single cleaning would probably not be to the slightest 

 appreciable injury to the glass, repeated wiping with any material, 

 however soft, will destroy the perfect polish, and result in obstruction 

 of light and consequent dimness in the field. Never use a chamois 

 leather on an optical surface, as these skins contain gritty particles. 

 Old, well-worn linen and Japanese paper are by far the best mate- 

 rials for wiping glasses. If a lens be covered with dust, brush it 

 off ; breathe on the surface, and wipe gently with the linen or paper. 

 Should you get clove oil on the front lens of the objective (as fre- 

 quently happens when examining temporary mounts) wipe it dry and 

 then clean with the linen moistened with a drop of alcohol. Dammar 

 varnish can be very readily removed from any surface after having 

 softened it with oil of cloves. The front lens of the objective, being 

 the only one exposed, is the one usually soiled. 



Particles of dirt on the objective, as I have said, cause a dimness in 

 the field the image is blurred. Dust on the lenses of *t he eye-piece, 

 however, appears in the field. These lenses are readily cleaned by 

 dusting, and wiping with the linen, after having breathed on the 

 surface. Never wipe a lens when dusting with a camel's hair brush 

 will answer the purpose. 



The microscope should either be covered with a shade or cloth, or 

 put away in its case, when not in use. The delicate mechanism of the 

 fine adjustment becomes worn and shaky if not kept free from dirt. 



