CD 1963056 E&MP 23.009
Electric Insulating and Insulators
The work of the high tension laboratory includes the testing of insulators, used in high tension power transmission to determine the voltage at which the insulating properties break down. This insulator, of "Pyrex" glass, withstood a potential of 125,000 volts before "flashing over" as shown. The photograph was made at the high tension laboratory at the University of Wisconsin.