This is a test of an insulator to be used by the Southern Power Company. The insulator is a Thomas tri-shelled multipart from around 1910. The test purpose was to see if the insulator could withstand the powerlines estimated "flashover" voltage and to see if it chipped, cracked, or damaged the insulator. The insulators passed the test and were used on a powerline in Great Falls, SC. ***This image is from Transactions / American Institute of Electrical Engineers, Volume 30, Part 1***