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 arrangement of the 

 scales produces beautiful " waves " of colour, which aro 

 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 

 (Chapter VI.). 



The manner of preparing and mounting many of the 

 Polyzoa and Zoophytes has been before described ; but any 



