74 



THE AMERICAN MOKTHLY 



[April, 



spread it over the cover ; put the 

 Hghted spirit-lamp beneath, so the 

 flame plays directly upon the metal 

 and causes rapid boiling, which dis- 

 tributes the forms well, and immedi- 

 ate drying ; continue heating as much 

 as the glass will bear for several 

 minutes. During the heating pre- 

 pare one of the slides by running a 

 second coat of alcoholic shellac over 

 the dried rings to act as a cement. 

 Then, w^hen the cover-glass is cool, 

 invert it over the cell, and press it 

 down on the fresh shellac until it is 

 in contact all arovmd. Set it aside 

 for a few minutes, and then apply a 

 third coat of shellac, running it over 

 the edge of the cover to ensure per- 

 fect sealing of the cell. The mount 

 is now perfectly safe, if it is not 

 handled roughly. It may be put 

 away until a number have accumu- 

 lated to be finished together. The 

 methods of finishing will be given 

 further on. 



It will be obvious that any trans- 

 parent objects may be mounted in 

 the same way, placing them upon 

 the slide itself instead of upon the 

 cover. The scales or "wing-dust of 

 moths and butterflies will aflbrd the 

 novice good specimens to experiment 

 with in this kind of mounting. 



Mounting Thiti Opaque Objects. 

 — The method of preparing the cells 

 is the same as that just described, 

 except that the cells are made opaque 

 inside of the shellac ring, being either 

 wholly covered with a black, opaque 

 varnish or paint, as is usually the 

 case, or a central spot only is cov- 

 ered, leaving an annular clear space 

 around it, as when the lieberkuhn is 

 to be used. For this purpose as- 

 phalt is frequently used, but ivory 

 drop black is much to be preferred, 

 as it gives a dead black surface. We 

 have used with much satisfaction a 

 fine black paint manufactured by 

 Messrs. F. W. Devoe & Co., of New- 

 York, which dries upon glass with- 

 out cracking, and gives a dead black 

 surface. It is ver}- useful in mount- 

 ing. 



The lieberkuhn is an illuminator 

 much less used than it deserves to 

 be. Light is thrown up from the 

 mirror all around the opaque spot 

 upon which the object is mounted, 

 and is reflected down upon the ob- 

 ject from the lieberkuhn, giving par- 

 ticularly fine effects. Mounting very 

 minute objects upon small opaque 

 spots is an excellent plan apart from 

 its advantages for the lieberkuhn, as 

 it makes neat slides. It is especially 

 ada2Dted to such specimens as the 

 spicules of sea-fans or gorgonias. We 

 have one slide w^ith four or five 

 opaque spots under one -l-inch cover- 

 glass, each of which has a different 

 variety of spicules from any of the 

 others. Each of these opaque spots 

 is surrounded b}^ a fine ring of as- 

 phalt. Objects are made to adhere 

 to the opaque ground by the use of a 

 dilute solution of gum. A drop of 

 gum-water is allowed to dry sponta- 

 neously upon the ground, when it 

 can be moistened sufficiently to be- 

 come sticky by gently breathing up- 

 on it. Spicules or other light objects 

 may then be sprinkled upon it, or 

 they may be arranged in groups, and 

 on drying they will be found securely 

 attached. 



The subject of mounting opaque 

 objects will be continued next month, 

 our space being already well filled 

 for this issue, when instructions for 

 finishing the cells will be given. 



( To be continued.^ 



— Messrs. Bausch & Lomb promise 

 some novelties in their forthcoming 

 catalogue, of some of which v\^e have 

 already seen the illustrations. Among 

 other things they have designed a new 

 microscope of the German style, which 

 will doubtless be favorably received. 

 It is true that this form of stand is not 

 popular in this covmtry, but for the 

 investigator it possesses certain ad- 

 vantages of convenience and small 

 size which will commend it to many 

 persons. 



