Koku had already seen the opening of a considerable cavity in one wall of the gorge. He advanced cautiously. The cavern appeared to be very deep. It was dark beyond the entrance. As the party hesitated before the opening they could distinctly feel a draught of air blowing from the hole.
“It’s a tunnel, I bet,” said Ned. “What say? Think it goes clear through this ice mountain to the plain beyond?”
“Why not?” demanded Tom. “These ice cliffs seem honeycombed with such caves.”
Koku suddenly shouted and darted forward into the mouth of the cave. There was a savage roar in reply—but it was no human voice that answered the giant’s challenge.
“A bear!” exclaimed Tom, and he was first to follow the excited Koku into the half darkened cavity.
Ned was close on the young inventor’s heels.
“Tom, do have a care!” he shouted.
“No time for care!” panted Tom. “Koku’s fearless! No telling what he’ll do!”
The giant thrust mightily with his spear and the challenging roar of the bear changed instantly to a scream of pain. With a crash of ice and breaking spear-handle, the huge beast appeared in the entrance to the cave.
Koku was overturned. He fell sprawling, with the broken handle still clutched in his mighty grip. The bear reared, plucking at the staff that impaled it. It stood taller than Captain Karofsen, or even Koku. It was a drab-white polar bear of fierce aspect, and its rumbling growls reverberated from the walls of ice, making a deafening clamor.