Undaunted, he had turned his sights upon a last great venture-the crossing of the Antarctic continent from the Weddell to the Ross Sea. By the time Shackleton headed south again in 1914, the prize of the South Pole, which he had twice sought, had been claimed by others. Yet for all the heroism of these earlier efforts, neither had accomplished what it had set out to do.

When Shackleton embarked upon his Imperial Trans-Antarctic Expedition, he was already a national hero with two polar expeditions behind him, including one that had taken him to within 100 miles of the South Pole, the farthest south anyone had travelled at that time. Meanwhile, the leisurely, unrelenting northerly drift of the Weddell Sea carried the Endurance within the pack farther and farther from the land it had come so close to reaching. Days later, the temperature plummeted to 9, as good as cementing the loose pack for the winter. A northeast gale blowing on and off for six straight days compressed the pack against the Antarctic ice shelf, trapping the ship fast within it. One hundred miles short of her intended harbor, new ice conditions brought the Endurance to a halt. Since December 1914, the Endurance had battled unusually heavy ice conditions, travelling more than 1,000 miles from the remote whaling stations on the island of South Georgia, at the gateway to the Antarctic Circle. Shackleton had been intent on an ambitious mission: He and his men had travelled to the south to claim one of the last remaining prizes in exploration, the crossing on foot of the Antarctic continent. Their ship, Endurance, was trapped at latitude 74 south, deep in the frozen waters of Antarctica's Weddell Sea. The speaker was Sir Ernest Shackleton, one of the most renowned polar explorers of his day, and the third man was Frank Wild, his second-in-command. It may be a few months, and it may be only a question of weeks, or even days.

You had better make up your mind that it is only a matter of time. Sometimes, the little ship would quiver and groan in response, her wooden timbers straining as the pressure from millions of tons of ice, set in motion by some faraway disturbance, at last reached her resting place and nipped at her resilient sides. Away in the distance, the ice would groan, and Worsley and his two companions would listen to its ominous voice as it travelled to them across the frozen miles. From time to time, the shriek of the wind outside broke all conversation. The temperature was -30 Fahrenheit, and around the ship, extending to the horizon in all directions, was a sea of ice, white and mysterious under the clear, hard stars. It was July, midwinter in Antarctica, and the darkness of the long polar night had been upon them for many weeks. The captain of the ship, Frank Worsley, would remember the day vividly ever afterward.

The Endurance by Caroline Alexander