Prior to Cook’s day, an accurate measurement of longitude was virtually impossible. There was no way to determine the exact time of day, the ship’s position, and the exact time at a fixed point on shore. After 1735, a device invented by Englishman John Harrison made this possible. He invented a sea clock called a chronometer, which kept perfect time under rough sea conditions. Because of this instrument, Cook was one of the first ship’s commanders to know his exact position on the globe while sailing uncharted seas. He carried four chronometers aboard the Resolution and the Adventure.
The ships headed south around the Cape of Good Hope and toward Antarctica. They crossed the Antarctic circle for the first time in January, 1773. Too much ice blocked Cook’s way to find the continent of Antarctica and eventually his ships headed for warmer waters to the east. After stops in New Zealand and Tahiti, Cook discovered more islands in the south Pacific. By November, 1773, theResolution was underway once again in search of the southern continent. After reaching the Antarctic Circle in January, 1774, Cook had sailed farther south than any other explorer. But he never sighted the continent of Antarctica. Having been separated from its sister ship, the Adventure made its way back to England. Cook returned to warmer waters and continued explorations of the Pacific. He arrived back in England on July 29, 1775.
Courtesy of: The Mariners Museum