When the way was barred by a floe of moderate thickness we would drive the ship at half speed against it, stopping the engines just before the impact. At the first blow the Endurance would cut a V-shaped nick in the face of the floe, the slope of her cutwater often causing her bows to rise till nearly clear of the water, when she would slide backwards, rolling slightly. Watching carefully that loose lumps of ice did not damage the propeller, we would reverse the engines and back the ship off 200 to 300 yards. She would then be driven full speed into the V, taking care to hit the center accurately. The operation would be repeated until a short dock was cut, into which the ship, acting as a large wedge, was driven. At about the fourth attempt, if it was to succeed at all, the floe would yield. A black, sinuous line, as though pen-drawn on white paper, would appear ahead, boradening as the eye traced it back to the ship. Presently it would be broad enough to receive her, and we would forge ahead. Under the bows and alongside, great slabs of ice were being turned over and slid back on the floe, or driven down and under the ice and ship. In this way the Endurance would split a 2-ft. to 3-ft. floe a square mile in extent. Occasionally the floe, although cracked across, would be so held by other floes that it would refuse to open wide, and so gradually would bring the ship to a standstill. We would then go astern for some distance and again drive her full speed into the crack, till finally the floe would yield to the repeated onslaughts.
— Ernest Shackleton, South