MOUNTING OF MICROSCOPIC OBJECTS. 13 



time, and more patience be consumed in getting it back, together 

 with the added risk of destroying it in the attempt. But if it be 

 placed m close contact with the surface of the slide, it will become 

 firmly fixed. The forceps having been wiped clean (it is still better 

 to have a second and heavier pair for this purpose), one of the 

 cleansed covers is taken up by them, slighly warmed over the lamp, 

 and gently laid upon the balsam, which will spread out under its 

 warmth, if the operation be successfully performed, as the cover 

 settles down to its level. This can be aided by carefully warming 

 the slide over the lamp, holding it in a perfectly level position, and 

 the warming should be continued until the fluid balsam has reached 

 the edge of the cover all around, when the slide should be set aside 

 in a moderately warm place for say 24 hours. On no account 

 should the cover be touched or pressed down at this time, and no 

 notice should be taken of any bubbles that may appear, as they will 

 move out to the edges and depart of their own accord. On the fol- 

 lowing day the slide may be again very gently warmed, and the cover 

 very slightly pressed down with the forceps, after which, if we 

 possess the luxury of a drying oven (see figure 9), we will place 

 it therein, and by the aid of a small kerosene lamp, maintain a tem- 

 perature of about 120 Fahrenheit for a week or ten days, when the 

 preparation may be taken out to remain, we trust, " a thing of 

 beauty and a joy forever." 



The same process that we have followed to its end with the 

 wing, suffices for all the other portions of our fly, and indeed, for 

 all specimens not thick enough to require a cell; for these special 

 directions will be given in a future article. 



If our work has been entirely successful, the slide is now fin- 

 ished, with the exception of labeling. But if (as is more likely), 

 there was an excess of balsam, which has exuded from beneath the 

 cover, it must be cleaned off with a knife, and being by this time 

 hard and resinous, this is very readily done, after which a little soap 

 and water will remove all traces of it. Most persons will prefer to 

 finish their slides with a ring of cement, and for this purpose a 

 turn-table, which I have enumerated among the non-essentials for 

 balsam mounts, must be provided. The slide having been accu- 

 rately centered, a ring of the shellac cement is to be applied, fol- 

 lowed by successive ones of white zinc, until the space between the 

 surfaces of the slide and covering glass is quite filled up, care being 



