The C. H. Pond insulator and Moses G. Farmer's new stoneware insulator

p. 109

ELECTRIC INSULATORS.—C. H. Pond proposes to manufacture insulators of a compound formed of one part of coal-tar, and two parts of charcoal, saw-dust, or tan-bark. These last ingredients must be thoroughly dried and incorporated with the tar. The articles are moulded of the desired shape and baked in an oven, and an insulator may thus be produced which is said to be hard, yet slightly flexible, and very cheap.

p. 120

A NEW insulator, introduced by Moses G. Farmer, is composed of earthen or stoneware baked in the usual manner and then saturated in a mixture of twenty-four parts of rosin, sixteen of bees-wax, eight of spermaceti, and one of oil.

p. 125

INSULATOR TESTS.

IN a test of glass insulators of the Compromise pattern, where the tie-wire is attached to the centre of the insulator, after one year's exposure and during a heavy rain, the resistance per insulator was found to be 4,030,000 ohms; and during a heavy fog 11,000,000 ohms.

In a test of glass insulators of the new Western Union pattern, after an exposure of one month, tested during a thirty-six hours' rain, the resistance per insulator was found to be 49 megohms.

In a test of the Pond insulator, under the same circumstances, and with a similar exposure, the resistance per insulator was found to be 850 megohms.

A test of the same glass insulators, after a forty-eight hours rain, showed a resistance of 30 megohms per insulator, and Pond's insulator, under the same circumstances, gave 525 megohms per insulator.