MOUNTING OBJECTS IN CANADA BALSAM. 



215 



Fig. 101. 



enow*, recourse may be had to a simple Spring-Press made by a 

 slight alteration of the 'American clothes-peg which is now in 

 general use in this country for a variety of purposes ; all that is 

 necessary being to rub-down the opposed surfaces of the clip 

 with a flat-file, so that they shall be parallel to each other when an 

 ordinary slide with its cover is interposed between them (Fig. 101). 

 This contrivance, 

 however, is defec- 

 tive in not allowing 

 of the graduated 

 pressure which may 

 be made by the 

 Mounting Instru- 

 ment. — Great care 

 should be taken to 

 keep these imple- Spring Press, 



ments free from 



soils of Balsam ; since the slides and glass-covers are certain 

 to receive them. The readiest mode of cleansing the Needles 

 (their 'temper' being a matter of no consequence for these pur- 

 poses) is to heat them red-hot in the lamp, so as to burn-off the 

 balsam ; and then carefully to wipe them. The Forceps, both of 

 wood and of metal, should be cleansed with Oil of Turpentine or 

 with Methylated Spirit. 



160. Much of the success of mounting Objects in this mode will 

 depend upon their previous preparation. Such hard objects as 

 sections of Shells or Echinus-spines, should be first well cleansed 

 with water, and should then be thoroughly dried. Insect structures, 

 on the other hand, are best macerated for some time in Oil of Tur- 

 pentine, which will remove any greasiness they may contain, and 

 will at the same time increase their transparence. When Forami- 

 nifera are to be mounted in Canada Balsam, long-continued 

 maceration in Oil of Turpentine generally causes its entrance into 

 their cavities ; so that as the Turpentine is afterwards replaced by 

 the Balsam, air-bubbles (of which it is otherwise very difficult 

 to get rid) are avoided. Not only dry but moist objects (such as 

 Fish-scales, Tongues of Mollusks, or Injected preparations) may be 

 mounted in Canada Balsam, by soaking them successively for ten 

 or fifteen minutes in Alcohol, Pyroxylic spirit, and Oil of Turpen- 

 tine ; the Water they at first contained being finally replaced by the 

 last of these menstrua, which in its turn gives place to the Balsam. 

 ~In mounting an ordinary Object, a sufficient quantity of liquid 

 balsam should be laid in the centre of the slide ; this should be 

 warmed but not boiled ; and any air-bubbles which may make 

 their appearance should either be caused to burst by touching them 

 with the needle-point, or should be drawn to one side. The object, 

 if it can be held in the fine-pointed forceps, should then be plunged 

 into the drop of balsam ; and, if it be not completely covered, a 



