th a large
salt mine. Once we are in there we can make our way out. We'll soon be
free."

"Ask him if he's heard anything of my airship?" asked Tom. Mr.
Petrofsky put the question rapidly in Russian and then translated the
answer.

"It's in the same place."

"Hurray!" cried Tom.

Working rapidly, the Nihilist guard soon had the cell doors open, for
he had the keys, and our friends stepped out into the corridor.

"This way," called Ivan Petrofsky, as he followed their liberator, who
spoke in whispers. "He says he will lead us to the salt mine, tell us
how to get out and then he must make his own escape."

"Then he isn't coming with us?" asked Ned.

"No, it would not be safe. But he will tell us how to get out. It seems
that years ago some prisoners escaped this way, and the authorities
closed up the tunnel. But a cave-in of the salt mine opened a way into
it again."

They followed their queer guide, who led them down the corridor. He
paused at the end, and then, diving in behind a pile of rubbish, he
pulled away some boards. A black opening, barely large enough for a man
to walk in upright, was disclosed.

"In there?" cried Tom.

"In there," answered Mr. Petrofsky. He and the guard murmured their
good-byes, and then, with a lighted candle the faithful Nihilist had
provided, and with several others in reserve, our friends stepped into
the blackness. They could hear the board being pulled back into place
behind them.

"Forward!" cried the exile, and forward they went.

It was not a pleasant journey, being through an uneven tunnel in the
darkness. Half a mile later they emerged into a large salt mine, that
seemed to be directly beneath the town. Work in this part had been
abandoned long ago, all the salt there was left being in the shape of
large pillars, that supported the roof. It sparkled dully in the candle
light.

"Now let me see if I remember the turnings," murmured Mr. Petrofsky.
"He said to keep on for half an hour, and we would come out in a little
woods not far from where our airship was anchored."

Twisting and turning, here and there in the semi-darkness, stumbling,
and sometimes falling over the uneven floor, the little party went on.

"Did you say half an hour?" asked Tom, after a while.

"Yes," replied the Russian.

"We've been longer than that," announced the young inventor, after a
look at his watch. "It's over an hour."

"Bless my timetable!" cried Mr. Damon.

"Are you sure?" ask