MOUNTING OF MICROSCOPIC OBJECTS. 23 



small vial, which fill with distilled or pure filtered water, and allow 

 the diatoms to settle to the bottom, when the fluid must be carefully 

 poured off, and the vial again filled with water. The object of this 

 is to get rid of almost every trace of the alcohol, which contained 

 the diatoms in the stock bottle, and which, if not removed, would 

 prevent them from being evenly distributed over the covers. I say 

 covers, for diatoms should always be mounted upon these, and not 

 upon the slides. Now place upon the table as many covers as you 

 desire to mount, separated some little distance from each other, and 

 with the glass tube drop a portion of the contents of the small vial 

 of diatoms in water upon each. The vial should be gently shaken 

 between each dip, to distribute the diatoms evenly, and the amount 

 of fluid placed on each cover should be sufficient to extend to the 

 edge, and assume a convex form over it. The diatoms will distri- 

 bute themselves evenly over the whole surface, care being taken not 

 to disturb them by any jarring of the table. The dip is to be 

 made from the vial by thrusting the tube down nearly to the bottom 

 and closing the top with the forefinger: the contents are deposited 

 upon each cover, by gently raising the finger and allowing the air to 

 enter. A little practice is necessary to perform this successfully 

 always. Our covers now being all ready, with watery burden cover- 

 ing the tiny diatoms, we light our spirit lamp 

 and carefully apply its flame beneath the 

 table, moving it back and forth and occasion- 

 ally withdrawing it altogether, our object 

 jbeing to slowly evaporate the water, without 

 :ausing it to boil or in any way' disturb the 

 I diatoms. As soon as the evaporation is com- 

 plete, the lamp may be left untouched and 

 the table heated to the highest degree pos- 

 sible, in order to insure a thorough drying of 



the diatoms, which are now ready for the 

 Fig. 15- Glass Vial,. fina , mounting 



Place a slide upon the mounting plate and a minute drop of 

 pure balsam in its centre, and grasping one of the hot covers with 

 the forceps, turn it over upon the balsam, which will quickly spread 

 out to its edges, and the mounting is complete: done as quickly as 

 I can tell of it. If desired, the slide may be heated over the lamp 

 until all the turpentine is driven off, when, upon cooling, the cover 



