74 HOLLAND: MICA DEPOSITS OF INDIA. 



It can also be rolled in thinner form as micanite cloth or paper for 

 repairing transformers, armatures, etc., and in this form it is sold in rolls 

 many feet long or in separate sheets cut to various sizes. The inven- 

 tion of micanite has created a new opening for the use of the smaller 

 grades of mica formerly rejected as waste, and in India, where simple 

 skilled labour is so cheap, the riving of thin films from waste heaps has 

 lately given new life to many mines. 



Thin sheets are used also where it is desirable to combine lightness 

 with a certain amount of rigidity, as in the vanes of an anemometer, 

 such as in Dickinson's or Biram's anemcyneter, used for testing the 

 ventilation currents in mines. Similar sheets can be silvered for 

 mirrors and reflectors bent to any required shape. They are also used 

 for lantern-slides painted with transparent pigments ; for covering 

 photographs and pictures, and as a substitute for glass-plates and 

 celluloid films in preparing photographic plates, from which the nega- 

 tive with a thin carrying film may be subsequently split. For mounting 

 soft and collapsible natural history specimens for exhibition in spirit, 

 thin sheets of mica are admirably adapted, and no convenient substitute 

 can be found to remain unaffected by the spirit and at the same time 

 transparent and soft enough to permit the free use of needle and 

 thread for purposes of attachment. For the preparation of microscopic 

 sections of small fossils, and for various optical purposes, the peculiar 

 properties of mica give the mineral uses which are interesting, though 

 of small value to the industry. 



Besides the large sheets and plates, the smaller waste scrap and 

 artificially pulverised mica have been turned to account in various 

 ways. As an electric insulator it has been used to replace porcelain 

 cups on telegraph poles. The chief use of ground mica depends on its 

 non-conductivity for heat, and it consequently forms no?i-conducting 

 packings and jackets for boilers and steam-pipes. For these purposes 

 mica appears to combine advantages which render it superior to all 

 other forms of laggings. The parallel disposition of the flakes increase 

 its resistance to the passage of heat by conduction or radiation to a 

 degree not possible in materials with fibres disposed in all directions. 

 ( 64 ) 



