222 Modern Microscopy 



with a needle-point until it adheres firmly to the slide all 

 round. If the specimen is small it must be fastened in 

 the cell with some gum, as for opaque mounts, then put it 

 away until the gum has dried, apply a cover, and finish 

 off as directed for opaque mounts. Leaves of plants and 

 wings of butterflies should be mounted on a thin slide, so 

 that both sides may be examined. No gum will be required 

 for these specimens, but a piece of the leaf or wing should 

 be cut or punched out as nearly the size of the cell as 

 possible, and a thin cell should be used, so that the cover 

 may rest on the object and keep it flat. In all dry mounts 

 great care must be taken that all the cements used to 

 fasten the object in position are quite dry before the cover 

 is put on ; if not, any moisture remaining will condense on 

 the under surface of the cover and spoil the preparation. 



Opaque Mounts of Pollens. — Make an opaque cell, 

 and apply a thin layer of gum water all over its floor ; 

 then take some perfectly dry pollen and put it in the cell, 

 shake the slide so that the pollen spreads evenly all over 

 the cell, and let it dry. Then apply some enamel to the 

 upper surface of the ring of the cell, and when this is about 

 half dry apply the cover-glass. 



LESSON XIV. 

 FINISHING OFF SLIDES. 



Canada Balsam — Quick Method. — Take a small saucer 

 of chloroform and a soft brush, and carefully wash away 

 the exuded balsam. Allow the slide to dry, then place it 

 in a turn-table and apply a coat of black shellac cement. 

 Let this dry, then wash the slide quite clean with turpen- 

 tine and apply another coat of cement. 



Canada Balsam — Exposure Method. — Put the slide into 

 a saucer of methylated spirit, and with a small piece of 

 soft rag gently rub away the excess of balsam ; dry the 



