Now to the right, now to the left, the cruiser advanced, as the men blasted her zigzag channel course. As each new forward step was taken, the pressure of the vast jam closed the way and the channel was left behind. It was slow work, but sure. Behind the adventurers the sun came slowly on his southern path, turning dim twilight into weak and pallid day. Steadily as they worked, ten days passed and saw the blasters little more than a third of the way across the enormous jam. All around them thundered and crashed the ice in the grip of the great breaking forces. At times the uproar of smitten bergs and cracking floes made the sound of their exploding lyddite seem a puny and futile mockery of nature's mighty hammers. On the decks of the _Minnetonka_ uneasy men paced restlessly, and worn by waiting and danger, cursed or prayed, according to their natures. In their long hutches, the Alaskan dogs, still more uneasy, snarled and howled. Seeking to turn the delay to some advantage, Polaris selected from the forty-odd dogs on the ship seven of the likeliest, and, with sledge and harness, left the ship to acquaint himself with them. It was time that they knew the master whom they must carry both fast and far. Huskies they were, from the finest of the Yukon strains, big and shaggy, their coats splotched with brown and white, but they were not the equals in size or strength of gray Marcus and his fellows, which the son of the snows had driven aforetime. He found them not at all lacking in temper. On a level spot in the floe, not far from the ship, Polaris laid out his harness, and chose his animals for the positions in which he would have them run. Largest of all the brutes was the tawny Boris, sullen and vicious, but intelligent. Polaris selected him as the team leader, and the lessons began. Awed at first by their strange surroundings, affrighted by the thundering ice and the occasional shuddering of the floe, the brutes flinched and whimpered, paying little attention to the man. Then over their backs and about their ears shrieked and cracked an eighteen-foot lash that demanded notice. With ears laid flat, the dogs cowered into a tense group, burning eyes alternating from the writhing whip, which snapped above them, but fell not, to the man who wielded it.