"We must defend ourselves!" cried Andy. "Those beasts will tear us apart! They are as savage as wolves! Oh, for my rifle!" "Haven't you a revolver?" cried Jack. "Of course! I forgot," said Andy, bringing out his two weapons. "Washington has one, too! Hurry up with it, Washington!" "I'll give mine to Jack!" yelled the negro, handing the boy the weapon, and then, taking to his heels, ran away from the on-coming brutes. The animals were now fifty feet off and advancing rapidly. Their eyes flashed with the mad rage of hunger and fear, while foam dripped from their jaws. Taking careful aim, Andy fired both revolvers at the pack of animals. They were so close together he could not help hitting some. Two fell, killed or badly wounded. Jack also fired and dropped one dog. But the others came on, never halting. "Fire as fast as you can!" cried Andy. "It is our only chance! We must stop them!" The old hunter and Jack pulled the triggers of their weapons rapidly. Spurts of flame and small clouds of smoke issued from the muzzles, and several more of the dogs were killed. There were at least a dozen dogs left when the revolver chambers were empty, and with wild bounds they leaped upon the adventurers. The yelping and barking sounded loud above the hoarse shouts of the men and boys, who, with their fists, prepared to fight the wild dogs. "Hit 'em with chunks of ice!" called Andy. His advice came just in time. Each one grabbed up a chunk of the frozen water. It was as hard as a stone. One big brute leaped for the professor's throat. In his weakened condition, caused by his exposure in the ice chamber, it seemed as if the old inventor would be killed. Suddenly a white object flew through the air. It struck the dog on the head, and the brute, with a howl, fell back. Jack had launched his chunk of ice just in time. "Good shot!" cried Andy. He hit another of the brutes over the skull with some of the frozen stuff, and Washington, whose courage had returned, did likewise. Tom and Bill disabled the two dogs nearest them. Mark aimed at once fierce beast, but missed his shot, and, slipping on the ice, fell right in the animal's path. In an instant the brute was upon him. "Lie on your back and cover your head with your arms!" shouted Andy, as he ran toward the animal. Mark did as he was told. The dog endeavored to bite him, but the stout furs on his back prevented much damage being done. Then, having secured a large chunk of ice, Andy ran up behind the beast and stretched it out with a well-directed blow. Mark was saved, and scrambled to his feet uninjured. Suddenly there sounded a series of sharp reports as if a rifle was being discharged. The refugees looked up, expecting to see some armed force coming to their aid. Instead, they beheld the Esquimaux driver approaching on the run. He was swinging his long-lashed whip, which he had secured from the crack in the ice where he had stuck it, and was snapping it vigorously.