USES OF MICA. 75 



It will stand any usual high temperature which would calcine hair-felt 

 or other organic fibre, and will not disintegrate by vibration in the 

 proximity of machinery ; it is free from moisture and acids which 

 would attack iron structures, and in the presence of moisture resists 

 decomposition. Being soft at the same time, its accidental inclusion 

 in a bearing would have none of the abrasive properties of, for instance 

 slag or glass-wool. For non-conducting jackets, mica waste is now 

 used on most of the railways in the United States and Canada. 



Scrap mica in a similar way can be used as a protection against 

 heat, a layer in the roof of a house, carriage or article of clothing form- 

 ing a most effectual guard against the sun's heat in tropical climates, 

 an appreciable relief being obtained by the use of a very thin layer. 

 Mr. Mervyn Smith informs the writer that a layer of mica-waste, 

 £-inch thick, placed under an ordinary tiled roof exposed to the hot- 

 weather sun in Bengal, made an average difference of 15 in the tem- 

 perature of the air immediately under the roof. The same device is of 

 course correspondingly effectual in keeping in the heat during a cold 

 weather night, and for a similar reason it may be used as a packing for 

 ice-boxes or freezing machines. 



Various other uses, besides ornamental, have been suggested for 

 pulverised mica. It has been used, mixed with graphite or grease, as 

 a lubricant for bearings working under heavy pressures ; as a base for 

 soap, and as an inert, absorbent medium, instead of infusorial earth, for 

 taking up nitro-glycerine in the manufacture of a form of dynamite. 



As far as India is concerned, the most extensive use of mica is for 

 decorative and ornamental purposes, either alone or coloured, and in 

 the form of plates, as well as in the pulverulent condition. Pliny 

 refers to the employment of it, under the name lapis specularis, to 

 produce a brilliant glistening effect on the arena of the ancient Roman 

 amphitheatre, whilst in America quantities of the mineral have been 

 found in the ancient graves of Indian tribes, by whom it appears to 

 have been used for ornamental purposes, and its occurrence in some 

 localities indicate a certain amount of commercial intercourse among 

 widely separated tribes during prehistoric times. 



F ( 65 ) 



