For centuries, it was believed that a great unknown continent encompassed much of the southern end of the globe. Attempting to locate this land in 1772-75, James Cook, a British explorer, became the first to cross the Antarctic Circle and to sail around the continent (although not sighting it). His voyage neither proved nor disproved the continent's existence, but did indicate that if there were any such land its size had been greatly exaggerated.
During 1819-21, a similar circumnavigation of Antarctica was made by Fabian von Bellingshausen, a Russian captain. He discovered and named Peter I and Alexander I islands, within the Antarctic Circle.