The Microscope. 331 



tion is always ab©ve the slips and that it is not allowed to dry 

 on them, since it can then be removed with great diflSculty, 

 usually not at all, as it appears to have a chemical action on the 

 glass. 



But as already intimated, the reader will scarcely ever need 

 any chemical preparation for the cleaning ©f his slips. I have 

 been using them for several years and never have I felt the need 

 of anything except warm water and soap, with the occasional 

 application of a little saliva. I am sure that the reader's expe- 

 rience will be the same. 



When the slips have been cleaned, it is necessary to keep them 

 clean, as well as free from scratches. To do these things some 

 microscopists pack them away in drawers, after having arranged 

 little pieces of blotting paper between the ends. Others arrange 

 them in little packages and surround the four sides of each 

 package with tissue paper, pasting it so that no dust can enter, 

 and so that there may be no sliding movement among the slips. 

 Each one is then easily removed by breaking the thin paper, 

 and without disturbing any of the others. 



An equally simple and as useful a method, is to store them in 

 rack boxes with tightly fitting covers. These rack boxes are 

 mcde of the proper size, and have along the sides strips of wood 

 cut in grooves, into which the ends of the slips are placed, and 

 from which they may be easily removed. The reader can doubt- 

 less devise some method of his own, that will serve the purpose 

 as well as an}*^ of the ways already described by working micro- 

 scopists. One's own methods are often more satisfactory to 

 one's self, than are the devices offered in the books or by micro- 

 scopical friends. The only purposes to be remembered and 

 aimed at, are the cleanliness of the slips and their freedom from 

 injury. The methods by which these things are accomplished 

 are of little importance. 



Slips and covers are made of crown glass, and for a reason 

 that the beginning microscopist would not be likely to guess. 

 There is usually a good reason for all things and methods micro- 

 scopical, although the microscopist that uses the one and does the 

 other may not be able to give that reason. Slips and covers are 

 made of crown glass because the front lens of the objective with 

 which they are to be used is made of it. The light, thus passing 

 through the same kind of glass, suffers the same amount of 

 22 



