Some of the earliest ship lamps burned whale oil, either refined from the blubber of a right whale or harvested from the head of a sperm whale. In the 18th and 19th centuries, sperm oil was particularly prized because it burned longer than blubber. That combined with its relative scarcity made it more expensive, which is why sperm whale was mostly used at sea by naval vessels whose governments could afford the additional cost.
Whale oil was often burned in a lamp called the besser, the German word for better, which was bastardized into the word betty by English-language speakers. The lamp the betty was better than was the crusie, in which a wick floated in a pool of oil. The betty covered that oil tight so it wouldn’t spill, and secured the wick so it wouldn’t sink into the oil and go out.
Inside a ship, lamps were mounted on gimbals so they could pivot and stay horizontal in rolling seas. The best lamps were made of copper and pewter, but many were made of brass, tin, or tin-plated iron. Outside, poop lanterns, or lanthorns, adorned a ship’s stern. While these lamps were often painted on their exteriors, they remained unfinished near the flame, the better to reflect their flickering flames into what must have seemed to be an infinite expanse of darkness.
After the Civil War, kerosene largely replaced whale oil in lamps. Eventually, color-coded running lights (green on starboard, red on port) were installed, aiding navigation in harbors and at sea.