OF MICROSCOPIC OBJECTS. 



quired portion may then be removed ; or if a piece of skin can be 

 procured as stripped off in cooking, the scales may be easily taken 

 from the inner surface. They must then be washed and thorough- 

 ly cleaned. After drying, soak for a day in turpentine, and mount 

 in the ordinary manner with balsam. This is a good polarising 

 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 are quite soothing to the eye after examining some of the 

 very gorgeous salts, &c. 



There are many scales of fish which are good subjects for the 

 polariscope when mounted in balsam ; but as they require no par- 

 ticular 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 Diction- 

 ary" mentions a mode of making an interesting object by plait- 

 ing two series of white horse-hairs at an angle, mounting in bal- 

 sam, and using with the polariscope. All hairs, however, must be 

 steeped in turpentine 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 men- 

 tion them in this place ; but as they must be removed from the 

 animals by dissection, particulars respecting them will not be en- 

 tered into until we come to the part in which that operation is 

 described (Chapter V.). 



The manner of preparing and mounting many of the Polyzoa 

 and Zoophytes has been before described ; but any notice of 

 polarizing objects would be incomplete without some allusion to 

 them. A small piece of the Flustra avicularis, well prepared, is 

 beautiful when examined in this manner. No selenite is needed, 

 and yet the colours are truly gorgeous. It is often met with upon 



