Although petroleum had been discovered in August, 1859 in Titisville, Pennsylvania, both lighting and machine lubrication still depended upon whale oil. Since electricity didn't arrive in Edgartown until the late 1890s whale oil was still in demand until then. Dr. Daniel Fisher, the richest man on the Island, owned the largest industry in Edgartown, a spermaceti candle factory and whale oil manufactory.
Captain Jernegan and other New England whalers had found that the seasonal search for whales in the Arctic Ocean enabled them to spend winters in the warmer South Pacific Ocean. Between seasonal voyages, oil and whalebone would be shipped back to New England, making room on board for more. That system was working well, and so they continued the hunt, keeping New Englanders' homes lighted and their machines lubricated.
Martha's Vineyard Museum