12 MOUNTING. 



The main points to be observed are, that the object 

 and varnish are completely dry, and that the cell is 

 thoroughly closed. If the latter be not the case, 

 more varnish must be applied to any little openings 

 which may have been left ; and it is better to apply 

 the varnish in very small quantities at a time, the 

 application being renewed as soon as the previous 

 layer is quite dry. 



Dry transparent objects are usually small and deli- 

 cate; for, unless they are so, their structure cannot 

 be well seen. In mounting these, a square piece of 

 note-paper or tracing-paper, with the centre cut out, 

 may be fastened to a clean slide with a little paste, 

 gum, or shellac varnish. When this is thoroughly 

 dry, the object is placed in the vacant space, a clean 

 dry cover laid on, and the varnish applied by means of 

 a hair-pencil to the edges in very small quantities. 

 This will run in between the under surface of the 

 edges of the cover and the upper surface of the paper, 

 and when dry will cement the two together. 



Supposing that the object is so delicate that it 

 cannot be removed from the surface of a slide, if it 

 will not be injured by heat, a good plan is to draw a 

 square or circle around the object with a little black 

 japan, then to heat the slide gradually until the japan 

 is not indented with the finger-nail when cold. A 

 clean slide is then laid upon the ring of japan, 

 the whole again gently warmed, until the varnish is 

 softened, and the cover lightly pressed so as to be in 

 contact all round with the varnish. The slide must 

 then be rapidly cooled, by being laid upon a piece of 

 metal, which prevents the varnish from running in so 

 as to spoil the object. 



Many dry transparent objects can be preserved by 

 mounting in Canada balsam. This is the best pro- 

 cess for mounting objects in general; but only those 

 can be so preserved which are not injured by drying, 

 and which are not rendered too transparent by the 



