Insulators made from crushed granite invented

Crushed granite insulators for electric light purposes may take the place of the glass insulator now in use. Crushed granite is a late invention of a New York man, who has not yet secured a patent upon it. The granite is crushed in a retort with about 3,600 degrees of heat. It is then subjected to an enormous hydraulic pressure and formed into any shape desired. Its particular advantage is that it will stand 20,000 volts, while 1,500 volts will split an ordinary glass insulator.