st I can burn kerosene in my motor," Tom
explained, for he had perfected an attachment to this end. "You can get
kerosene almost anywhere in Russia."

At last word was received from Russia, from some Revolutionist friends
of the exile, stating that his brother was supposed to be working in a
certain sulphur mine north of the Iablonnoi mountains, and half way
between that range and the city of Iakutsk.

"But it might be a salt mine, just as well," said Mr. Petrofsky, when
he told the boys the news. "Information about the poor exiles is hard
to get."

"Well, we'll take a chance!" cried Tom determinedly.

The preparations went on, and by strict watchfulness none of the spies
secured admission to the shop where the air glider was being finished.
The big airship was gotten in shape for the voyage, and then, after a
final trial of the glider, it was taken apart and put aboard the
Falcon, ready for use on the gale-swept plains of Siberia.

The last of the stores, provisions and supplies were put in the big car
of the airship, a route had been carefully mapped out, and Tom, after
saying good-bye to Mary Nestor, his father, the housekeeper, and
Eradicate, took his place in the pilot house of the airship one
pleasant morning at the beginning of Summer.

"Don't you wish you were going, Rad?" the young inventor asked, for the
colored man had decided to stay at home.

"No indeedy, Massa Tom," was the answer. "Dat's a mighty cold country
in Shebeara, an' I laik warm wedder."

"Well, take care of yourself and Boomerang," answered Tom with a laugh.
Then he pulled the lever that sent a supply of gas into the big bag,
and the ship began to rise.

"I guess we've given those spies the slip," remarked Ned, as they rose
from the ground calling good-byes to the friends they left behind.

"I hope so," agreed Tom, but could he have seen two men, of sinister
looks, peering at the slowly-moving airship from the shelter of a glove
of trees, not far off, he might have changed his opinion, and so would
Ned.

Then, as the airship gathered momentum, it fairly sprang into the air,
and a moment later, the big propellers began revolving. They were off
on their long voyage to find the lost platinum mine, and rescue the
exile of Siberia.

CHAPTER XI

A STORM AT SEA

Tom had the choice of two routes in making his voyage to far-off
Siberia. He could have crossed the United States, sailed over the
Pacific ocean, and approached the l