d Ned.

"No matter," said Tom. "If we find any platinum we'll stay here all
night, and longer if necessary to get a good supply. This is better
than the city of gold, for we're in the open."

"I should say we were," observed Mr. Damon, as he bent to the blast,
which was strong, sheltered even as they were.

"Will it be safe to remain all night?" asked Mr. Borious, with a glance
about the desolate country.

"We have plenty of food," replied Tom, "and a good place to stay, in
the car of the glider. I don't believe we'll be attacked."

"No, not here," said the elder Petrofsky. "But we still have to go back
across Siberia to escape."

"We'll do it!" cried Tom. "Now for the platinum treasure!"

They went forward, and it was no easy work. For the wind still blew with
tremendous force though nothing like what it did higher up. And the
ground was uneven. They had to cling to each other and it was very
evident that no airship, not even the powerful Falcon, could have
reached the place. Only an air glider would answer.

It took them half an hour to get to the opening of the ancient mine,
and by that time it was nearly dark. But Tom had thought to bring
electric torches, such as he had used in the underground city of gold,
and they dispelled the gloom of the small cavern.

"Will you go in?" asked Ivan Petrofsky, when they had come to the
place. He looked at Tom.

"Go in? Of course I'll go in!" cried our hero, stepping forward. The
others followed. For some time they went on, and saw no traces of the
precious metal. Then Ned uttered a cry, as he saw some dull, grayish
particles imbedded in the earth walls of the shaft.

"Look!" he cried.

Tom was at his chum's side in a moment

"That's platinum!" cried the young inventor. "And of the very highest
grade! But the lumps are very small."

"There are larger ones beyond," said the younger Russian brother.

Forward they pressed, and a moment later coming around a turn in the
cavern where some earth had fallen away, evidently recently, Tom could
not repress a cry of joy. For there, in plain sight, were many large
lumps of the valuable metal, in as pure a state as it is ever found.
For it is always mixed with other metals or chemicals.

"Look at that!" cried Tom. "Look at that! Lumps as large as an egg!"
and he dug some out with a small pick he had brought along, and stuffed
them into his pocket.

"Bless my check book!" cried Mr. Damon, "and that stuff is as valuable