208 The Microscope. 



In diying, air spaces will often appear at the edge of the cover- 

 glass. Applying balsam will fill these spaces. 



Without heat, three or four weeks must elapse before it will be 

 safe to clean the slip. Most of the surplus balsam may be removed 

 with a knife blade heated in an alcohol flame. Chloroform on a 

 handkerchief will quickly remove the remainder; but the chloro- 

 form softens the balsam about the edge of the cover, therefore do not 

 dwell long in this process, but put the slip away to reharden, after 

 which make a final cleaning by the use of soap suds and a soft brush, 

 rinsing after with water and wiping with a handkerchief. 



The completion of an insect mount may be hastened by cleaning 

 off the balsam two or three days after mounting, using chloroform 

 with great care as to disturbing the cover-glass, then placing the 

 slip in a turn table, apply several coats of shellac dissolved in 

 alcohol about the cover-glass, giving time for each coat to dry, which 

 it will quickly do. 



This of itself will be a nice finish ; but if desired the shellac ring 

 may be covered with white zinc cement in the usual way. On this 

 circle fine colored lines may be made with a small brush, using 

 Canada balsam which has been tinted with any desired color of tube 

 oil paint thinned with benzol. 



The circle of shellac will prevent the subsequently-applied white 

 zinc cement from running under the cover, which would certainly 

 happen if the shellac were omitted. It may be trite to add that in 

 insect preparation as in all microscopical work, the utmost clean- 

 liness should be obsei'ved and dust avoided as much as possible. For 

 this purpose it is best not to have a woolen carpet in the work 

 room. Some of its dust will be sure to appear in the mounted slide. 



Some interesting insects are too large for ordinary 3x1 in. slips. 

 For these can be obtained 3x1^ in. slips from the Palmer Slide Co., 

 Geneva, N. Y., with covers round or square to match. This com- 

 pany, for a very reasonable charge, will grind the edges of covers, 

 thus enabling a nicer finish. 



MOUNTING INSECTS AS OPAQUE OBJECTS. 



In this work none of the preceding processes of preparation are 

 required. The most to be done is in providing a suitable cell, which 

 is quite fully explained in the text books. It is desirable to have a 

 good, dark background on which to place the insect. This may be 

 made by brushing a coat of water-color lamp-black on the bottom of 

 the cell. When dry, put in a drop of Asphalt cement, on which place 

 and press down a cover-glass small enough to go inside the cell. On 



