CARE OF THE MICROSCOPE 43 



of the forceps may be placed beneath the cover -glass, the tip of the 

 forefinger pressing lightly over it, and you will be enabled to carry 

 the thin glass wherever desired. 



As the cover settles down the air is pressed out, until finally the 

 section appears imbedded in the varnish the latter filling the space 

 between the cover and the slide. 



The object is "mounted." You have a permanent specimen. 

 The slide must be kept flat, as the balsam is soft. After some 

 weeks, the varnish around the edges 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 we have described it, after having been properly 

 labeled. 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 particulars you may prefer. 



Specimens should be kept in trays or boxes in such manner that 

 they may always lie flat. 



CARE OF THE MICROSCOPE 



The objectives constitute the most valuable part of the instru- 

 ment. 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 be cleaned, but it should be done with 

 great care. While the effect of a single cleaning would probably 

 not be of the slightest appreciable injury to the glass, repeated 

 wiping w r ith 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 materials 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 frequently happens when 

 examining temporary mounts) wipe it dry, and then clean with the 

 linen moistened with a drop of alcohol. Canada balsam 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 dim- 

 ness in the field the image is blurred. Dust on the lenses of the 



