OF THE MICROSCOPE. 233 



nish, it prevents the evaporation of the turpentine, and the 

 ultimate drying and cracking of the balsam. Where glycerine 

 jelly, glycerine, or glycerine and gum are used, it becomes 

 indispensable. 



The process employed for finishing slides in this way is as 

 follows: The objects having been mounted, the slides are laid 

 away until the balsam, cement, etc., have been hardened, when 

 all superfluous matters of this kind are easily removed with a 

 small chisel made out of a brad-awl ground thin and sharp. A 

 small chisel-pointed piece of hard wood, and a little water, will 

 remove the last traces of balsam or varnish, and if necessary a 

 final cleaning may be given with a rag moistened with alcohol. 

 The slide is then placed on the turn-table, and a neat ring of 

 varnish, either plain or colored, is run around the edge. The 

 varnish used for this purpose should be selected according to 

 the material in which the object is mounted. Thus, for ob- 

 jects in glycerine, glycerine jelly, or gum, the best coating is 

 shellac varnish, which may be left quite transparent and 

 colored with some of the aniline colors. Shellac also answers 

 on Canada balsam, wh^n the latter has become hard, but gold 

 size is better, and the gold size may either be colored with 

 the ordinary artists' colors, which are sold in tubes, and 

 which give an opaque-colored ring, or transparent colors may 

 be used. 



Labeling the Slides. The proper labeling of slides and 

 material is a most important matter. All bottles should bo 

 labeled, not only on the bottles themselves, but on the corks 

 or stoppers, and the slides should be kept labeled or numbered 

 during every stage of their progress. Our system is as follows: 

 Before the object is mounted the slide is labeled on the under 

 side with a very thin gummed label. Numbering with tho 

 writing diamond is deferred until the mount is completed, be- 

 cause, if spoilt, the whole may be thrown into a jar to be soaked 

 off, and this cannot be done with figures written or scratche 1 

 in with a diamond. As soon as the slide is finished the regular 

 label is attached, and the slide numbered with a writing dia- 

 mond. Of this number a record is kept, so that even if the label 

 should fall off or get soaked off, a nevr label may l>3 provided ; 



