142 THE MICROSCOPE. 



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 maybe 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 illustration), 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 w-ith 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 

 taken to allow each coat to harden before applying a fresh one, 

 which is rapidly accomplished with this invaluable cement. A nar- 

 row ring of some bright color makes a pleasing finish, and can be 

 readily made by adding to the ordinary damar medium a sufficient 

 quantity of any desired color, ground in a little oil. All these ce- 

 ments should be applied by small red sable brushes, and the best 

 mode of using them is to have the bottles in which they are con- 

 tained, filled with long, tapering corks, into the under side of which 

 the brushes are to be fastened. They are thus always immersed in 

 the cement when not in use, and never can become stiff and dry; 

 whilst they undergo no apparent deterioration. I am now using in 

 my white zinc bottle the same brush that I placed there six years ago. 



