THE MICROSCOPE. 



and finishing of the mount, properly, is of prime importance to its 

 continuance, I shall include some articles among the essentials 

 which might be considered luxuries in balsam mounting. Per- 

 fectly flat slips 7nust be procured, and good covering glasses, 

 flat also. If glass cells are to be used, I should advi.se 

 purchasing them ready made, as but few have patience suf- 

 ficient to prepare them properly for themselves. They are not 

 so very costly if purchased unattached to the slips, and the method 

 of so doing with marine glue will be given presently. The same 

 may be said of block tin cells, which cost about one half as much 

 as those of glass. To resume, wax in sheets, with a proper punch, 

 as described in my paper on balsam mounting ; a turn-table — self- 

 centering, by all means ; white zinc cement, properly made ; a few 

 needles in handles, a pair of curved forceps, some delicate spring 

 clips, or a Smith's mounting instrument ; a good sized camel's hair 

 brush, some absorbent cotton or blotting paper, and capillary or 

 dropping bottles to contain the preservative fluids will be about all 

 the tools we shall require for our work. 



% Fig. 17. Self-Centering Turn-Table. 



The simplest form of cell is of course one constructed of 

 cement only, and we will make our beginning with this. What have 

 we ready that so shallow a receptacle is suited to ? Here is a 

 potato ; let us scrape a small portion of its juicy whiteness into this 

 beaker and add a little cold waiter. The white mass which settles 

 at the bottom of the glass is almost all starch, many of the grains 

 free, others bound together in their parent cells, as our microscope 

 will presently show. After repeated washings, in cold water, and 



