180 



SELECTION AND USE 



if gold size be used as the varnish, 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 turntable, and a neat ring of 

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



The proper labeling of the slides is an important matter. 

 Oar system is as follows: As soon as the object is mounted, the 

 slide is labeled on the under side with a very thin gummed 

 label, and it is also numbered on the upper side with a writing 

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

 label should fall off or get soaked off, a new label may be pro- 

 vided. As soon as the slide is finished, the regular label is 

 attached, and the small label removed. As regards designs, 

 etc., for labels, the variety is -endless. Each microscopist will 

 probably select the one that accords most nearly with his own 

 taste. 



The Mai t wood Finder. This is a most important ac- 

 cessory to every microscope, as it not only facilitates inter- 

 change of notes between 

 microscopists living at a dis- 

 tance from each other, but 

 it enables observers to make 

 sure of the identity of the 

 objects under examination 

 at different times. It con- 

 sists of a glass slip, a little Fi S- 49< 

 wider than an ordinary slide, 



upon which is a photograph occupying a space 1 by 1 inch. 

 This space is divided into 2,500 squares (50 divisions on each 



