118 PREPARATION AND MOUNTING 
cooking, the scales may be easily taken from the inner 
surface. They must then be washed and thoroughly 
cleaned. After drying, soak for a day in turpentine, and 
mount in the ordinary manner with balsam. This is a 
good polarizing object; but the interest, and I think the 
beauty, is increased by procuring a piece of eel’s skin with 
the scales in situ, washing and drying under pressure, and 
mounting in balsam as before. The arfangement of the 
scales produces beautiful “ waves” of colour, which are 
quite soothing to the eye after examining some of the very ~ 
gorgeous salts. 
There are many scales of fish which are good subjects for 
the polariscope when mounted in balsam; but as they re- 
quire no particular treatment, they need no mention by 
name. | 
Among hairs we find some which are beautiful when 
mounted in balsam and examined by polarized light, Some, 
when wanted as common objects, are always used dry, as 
before mentioned ; but if they are intended to be shown as 
polarizing objects, they must be placed in some medium. 
The Micrographic Dictionary mentions a mode of making 
an interesting object by plaiting two series of white horse- 
hairs at an angle, mounting in balsam, and using with the 
polariscope. All hairs, however, must be steeped in tur- 
pentine for a short time before mounting, as they will thus 
be rendered cleaner and more transparent. When this is 
done, there is no difficulty in mounting them. 
Many of the “tongues” of fresh-water and marine 
mollusca are deeply interesting and most beautiful objects 
when examined by polarized light. As these are usually 
mounted in balsam, I mention them in this place; but as 
they must be removed from the animals by dissection, 
particulars respecting them will not be entered into until 
we come ‘to the part in which that operation is described 
(Ckapter VI.). | 
The manner of preparing and mounting many of the 
Polyzoa and Zoophytes has been before described; but any 
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