1893.] MICROvSCOPICAL JOURNAL. 261 



curely ; however carefully done, there is almost sure to be some 

 excess of balsam })ressed out at the edges. It is better to remove 

 this at once while the balsam is soft, with the point of a pen- 

 knife, having a small quantity of wood spirit (methyle alcohol) 

 by your side in a porcelain capsule to dip in the point of the 

 knife to keep it from getting sticky; jjut the slide on one side for 

 a day or two to harden, when if necessary the edges can be fur- 

 ther trimmed with the point of the pen-knife dipped in wood 

 spirit. 



The slide can then be cleaned with a bit of clean rag dip- 

 ped in wood spirit and after two or three wipings all round, it 

 will be clean enough to ring with black asphalt. Wood spirit 

 seems to be by far the best solvent of Canada balsam, not smear- 

 ing so much as spirits of wine or turpentine. The slides can be 

 left without ringing if preferred by warming them on the 

 hot-plate after cleaning. The edge of the balsam will become 

 bright and glassy, but as in time the balsam hardens and is 

 likely to spring off, it is better to take the trouble of putting a 

 black ring round. Centre the circle carefully on the turn-table. 

 By holding the point of a knife near the edge of the glass cover 

 and turning the table slowly round you can see at once which 

 way it is out of the centre, then adjust and so on till it is right. 

 A nice round sable brush mounted in metal, not too large, should 

 be selected ; dip it in the black varnish ; whirl the table round 

 and apply the brush in a sloping position so as to cover the edge 

 of the circle and touch the slide, the table being turned in direct- 

 ion so as not to meet the brush. Do not take up much varnish on 

 the brush, nor turn the table too quickly, for streaks of varnish 

 will be likely to cross the cover from one side to another; nor 

 should the brush be pressed too much. A capsule containing 

 a little benzole should be kept ready at the side to dip the brush 

 in when it gets clogged and should the black ring look thickened 

 in places and uneven in height, dip the cleaned brush in ben- 

 zole and run it on the turn table over the ring, when it will, be- 

 come smooth and bright. 



Put the finished slides away in a box for a day or two to 

 harden, when the slides can be cleaned and labelled. It is al- 

 ways desirable to record on the label the date and the medium 

 in which the preparation is mounted. 



{To he continued). 



