DRY TRANSPARENT OBJECTS. 13 



balsam. If the object to be mounted in balsam be 

 small, it is thoroughly dried, and then a drop of oil 

 of turpentine added to it upon a slide ; the slide is 

 then gently warmed, which causes the turpentine to 

 evaporate. When this has nearly all evaporated, a 

 drop of balsam is allowed to fall upon the object from 

 the end of a wire held at a distance above the flame 

 of a spirit-lamp. A warmed cover is next laid upon 

 the balsam, and gentle pressure applied until the 

 cover is sufficiently depressed. The slide is then 

 kept at a gentle heat until the balsam is quite hard 

 when cold. The superfluous portions may be re- 

 moved with the point of a knife, and any residues 

 cleaned off with turpentine or a little benzole on a 

 cloth. 



Another way consists in laying a cover upon the 

 dry object on a slide, adding a drop of turpentine, 

 and warming the whole over a spirit-lamp until all 

 air-bubbles are displaced, then continuing the appli- 

 cation of the heat until most of the turpentine has 

 evaporated. A drop or more of the balsam may next 

 be applied to the edge of the cover, when it will run 

 in and mix with the turpentine. The whole is then 

 gently heated until the balsam is hard when cold, 

 more balsam being added if necessary, to replace the 

 turpentine which has evaporated. 



When the objects are large, they should be pressed 

 as flat as possible without injury between two slides, 

 being retained until dry by enclosure between the 

 prongs of an American clothes-peg; or the slides 

 may be fastened at the ends by sealing-wax. When 

 perfectly dry, the object should be immersed in tur- 

 pentine, kept in a common gallipot, until all the air- 

 bubbles have been entirely displaced, and the object 

 appears very transparent. It is then removed from 

 the turpentine with forceps, drained, laid upon a 

 slide, and melted balsam dropped upon it until it is 

 quite covered. A clean dry slide is then laid upon 



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