loon and aeroplane,
and could be used as either, the necessary gas being made on board. It
was large enough to enable the air glider to be taken on it in sections.

It was about a week after their first meeting with him, that Ivan
Petrofsky paid a visit to the Swift home. He was warmly welcomed by the
aged inventor and Mr. Damon, and, closeted in the library of the house,
he proceeded to go more into details of his own and his brother's exile
to Siberia, and to tell about the supposed location of the lost
platinum mine.

"I don't believe we can start for several weeks yet," said Tom, after
some discussion. "It will take me that long to make the glider."

"And I, too, need a little time," said the Russian. "I will write to
some friends in St. Petersburg and perhaps they can get some
information for us, as to where my brother is.

"That will be good," declared Mr. Damon. "Bless my icicle! But the more
I think of this trip the better I like it!"

It was arranged that the Russian should call again soon, when the plans
would be nearer in shape, and in the meanwhile he must learn all he
could from revolutionary friends in Siberia.

It was a week after this, during which Tom, Ned and the others had been
very busy, that Tom decided to take a trip to see their Russian friend.
They had not heard from him since his visit, and Tom wanted to learn
something about the strength of the Siberian winds.

He and Ned went in one of the small airships and soon they were
hovering over the grounds surrounding the lonely house where Ivan
Petrofsky lived.

"He doesn't seem to be at home," remarked Ned, as they descended and
approached the dwelling.

"No, and it looks quite deserted," agreed the young inventor. "Say, all
the doors are open, too! He shouldn't go away and leave his house open
like that--with the valuable platinum there."

"Maybe he's asleep," suggested Ned.

They knocked on the opened door, but there was no answer. Then they
went inside. To their surprise the house was in confusion. Furniture
was overturned, tables and chairs were broken, and papers were
scattered about the room.

"There's been a fight here!" cried Tom.

"That's right," agreed Ned. "Maybe he's been hurt--maybe burglars came
for the platinum!"

"Come on!" cried Tom, making a dash for the stairs. "We'll see if he's
here."

The house was small, and it took but a moment to show that Mr.
Petrofsky was not there. Upstairs, as below, was the same
con