They had been dozing several hours when a series of wild yelps and barks outside roused them.  With an exclamation the driver jumped to his feet and rushed toward where he had tied the dogs.

The professor and the others crawled from the tent to see what the trouble was.  They saw that which filled them with fear.

The Esquimaux dogs, never any too tame, had gone half mad and wild from fear at seeing the water all around them, and from lack of food.  They were fighting among themselves, snarling, biting and barking viciously.

Just before the driver reached them they broke loose from the thongs that held them, and started for the tent.  The Esquimaux tried to stop them, but two of the savage brutes sprang at him and soon had him down on the ice.  The other dogs rushed on toward the group of adventurers, who stood still, awaiting the onslaught, and not knowing what to do.

“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.