But Altamont must know the why and wherefore of everything.

"But Doctor," he said, "can you reckon on your match so exactly that you can be quite sure it will fire the mine at the right moment?"

"I don't need to reckon at all; that's a difficulty easily got over."

"Then you have a match a hundred feet long?"

"No."

"You are simply going to lay a train of powder."

"No, that might miss fire."

"Well, there is no way then but for one of us to devote his life to the others, and go and light the powder himself."

"I'm ready," said Johnson, eagerly, "ready and willing."

"Quite useless my brave fellow," replied the Doctor, holding out his hand. "All our lives are precious, and they will be all spared, thank God!"

"Well, I give it up!" said the American. "I'll make no more guesses."

"I should like to know what is the good of learning physics," said the Doctor, smiling, "if they can't help a man at a pinch like this. Haven't we an electric battery, and long enough lines attached to it to serve our purpose? We can fire our mine whenever we please in an instant, and without the slightest danger."

"Hurrah!" exclaimed Johnson.

"Hurrah!" echoed the others, without heeding whether the enemy heard them or not.

The Doctor's idea was immediately carried out, and the connecting lines uncoiled and laid down from the house to the chamber of the mine, one end of each remaining attached to the electric pile, and the other inserted into the keg of powder.

By nine o'clock everything was ready. It was high time, for the bears were furiously engaged in the work of demolition. Johnson was stationed in the powder-magazine, in charge of the cord which held the bait.

"Now," said Clawbonny to his companions, "load your guns, in case our assailants are not killed. Stand beside Johnson, and the moment the explosion is over rush out."

[Illustration: ]

"All right," said Altamont.

"And now we have done all we can to help ourselves. So may Heaven help us!"

Hatteras, Altamont, and Bell repaired to the powder-magazine, while the Doctor remained alone beside the pile.

Soon he heard Johnson's voice in the distance calling out "Ready."

"All right," was the reply.

Johnson pulled his rope vigorously, and then rushed to the loop-hole to see the effect. The thin shell of ice had given way, and the body of the fox lay among the ruins. The bears were somewhat scared at first, but the next minute had eagerly rushed to seize the booty.

"Fire!" called out Johnson, and at once the electric spark was sent along the lines right into the keg of powder. A formidable explosion ensued; the house was shaken as if by an earthquake, and the walls cracked asunder. Hatteras, Altamont, and Bell hurried out with the guns, but they might spare their shot, for four of the bears lay dead, and the fifth, half roasted, though alive, was scampering away in terror as fast as his legs could carry him.

"Hurrah! Three cheers for Clawbonny," they shouted and overwhelmed the Doctor with plaudits and thanks.

CHAPTER XIV.

AN ARCTIC SPRING.

The prisoners were free, and their joy found vent in the noisiest demonstrations. They employed the rest of the day in repairing the house, which had suffered greatly by the explosion. They cleared away the blocks piled up by the animals, and filled up the rents in the walls, working with might and main, enlivened by the many songs of old Johnson.

Next morning there was a singular rise in the temperature, the thermometer going up to 15° above zero.

This comparative heat lasted several days. In sheltered spots the glass rose as high as 31°, and symptoms of a thaw appeared.

The ice began to crack here and there, and jets of salt water were thrown up, like fountains in an English park. A few days later, the rain fell in torrents.

Thick vapour rose from the snow, giving promise of the speedy disappearance of these immense masses. The sun's pale disc became deeper in colour, and remained longer above the horizon. The night was scarcely longer than three hours.

[Illustration: ]

Other tokens of spring's approach were manifest of equal significance, the birds were returning in flocks, and the air resounded with their deafening cries.