56 PREPARATION AND MOUNTING 



so as to show the feet, &c., extended, they must be dried with a 

 gentle pressure betwixt blotting-paper if possible. But this will 

 be treated more fully in Chapter III. 



The eyes of insects are sometimes allowed to dry in their natural 

 shape, and mounted as opaque objects ; but generally they are 

 used as transparencies in balsam or liquid, so the description of 

 the treatment which they require will be deferred to Chapter III. 



Hairs, when not too dark, are sometimes transparent enough 

 when mounted dry, but are usually mounted in balsam. These 

 also will be more fully noticed in another place. 



These are a few of the objects which are often mounted dry, but 

 some of them should be shown in balsam or liquid also, and there 

 is much difference of opinion as to the best way of preserving 

 others. This, however, is explained by the transparency which 

 the balsam gives interfering with one property of the object and 

 yet developing another which would have remained invisible if 

 preserved dry. The only method of overcoming this difficulty is 

 to keep the object mounted in both ways, which is comparatively 

 little trouble. 



I may here mention that many prefer the lieberkuhn for the 

 illumination of opaque objects ; and a good back-ground is gained 

 by putting upon the under side of the slide, immediately beneath 

 the object, a spot of black varnish, which does not interfere 

 materially with the light. 



