ole of extreme narrowness. The same glimpse
made clear to Hamp that some one had created the depression by breaking
through the crust of snow and gliding into an underlying cavity of
unknown depth. For a fraction of a second Hamp stuck on the brink. He
clutched vainly at air and snow. Then he shot down the abyss, feet
first, and vanished through the black fissure at the bottom!

Jerry heard his companion's horrified cries. He knew that some
catastrophe must have happened. He forgot all about his recent
discovery, and plunged recklessly forward. The natural result was that
the sleds banged him violently from the rear. Then came a dizzy drop
through space, and a collision with something soft, that yelled lustily
in Hamp's familiar tones.

"I--I couldn't help it," grasped Jerry, as he rolled to one side.

A second later it was his turn to sing out. A rifle, a haunch of
venison, and half-a-dozen tin dishes pelted him in quick succession on
the head and shoulders. He looked up with blinking eyes. Then he
understood what the avalanche meant.

Ten feet overhead was the gap through which he had fallen. Both sleds
had stuck there, and blocked it so completely that only a slim crevice
of light was visible. The straps on one of the sleds had broken,
allowing part of the contents to fall through.

Jerry held his breath for an instant, expecting another avalanche. When
nothing more fell, he recovered his presence of mind.

"That you, Hamp?" he whispered. "Are you hurt?"

"I don't think so. I fell on a pile of snow."

"Neither am I," declared Jerry. "It was a lucky escape for both of us. I
haven't got a bruise."

"No wonder," replied Hamp, in an injured tone. "You landed right on top
of me. I'm just getting my wind back."

"I'm awfully sorry," said Jerry, "but I couldn't help it."

"Oh, that's all right. Only if I had known you were coming, I would have
crawled out of the way. Where are we, anyhow?"

"That's what I want to know," Jerry replied. "It must be a cavern, Hamp.
The entrance was on top, and it got snowed over in the big storm."

"Some one broke through the crust before us," said Hamp, "for I saw the
marks as I was falling."

"Then he's in here now, whoever he is," whispered Jerry, in a startled
voice. "He couldn't have reached the hole to get out."

There was a moment of terrible silence. The boys huddled close together
and shivered with fear. Their hearts beat loudly and rapidly.

"I don't hear anything,