Like a bird descending from some dizzy height, the Vulture landed close to the pool of black water. It was a small lake and the darkness must have been caused by its depth, for later when they took some out in a glass it was as clear as a crystal. Then, too, there might have been black rocks on the bottom.

"Can it he possible that we are here at last?" cried Tom, above the noise of the gale, for the wind was blowing at a terrific rate. But our friends knew better now how to adjust themselves to it, and the lake was down in a valley, the sides of which cut off the power of the gale. As for the glider it was only necessary to equalize the balance and it would remain stationary in any wind.

"This is the place! This is the place!" cried Ivan Petrofsky. "Don't you remember, Peter?"

"Indeed I do! I have good cause to! This is where we found the platinum!"

"Bless my soul!" cried Mr. Damon. "Where is it, in the lake?"

"The mine itself is just beyond that barrier of broken and twisted trees," replied the elder Russian brother. "It is an irregular opening in the ground, as though once, centuries ago, an ancient people tried to get out the precious metal. We will go to it at once."

"But it is getting late," objected 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 New 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 bad brought along, and stuffed them into his pocket.

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

"More so!" cried Tom enthusiastically.

"Oh, here's a whopping big one!" cried Ned. I'll bet it weighs ten pounds."

"More than that!" cried Tom, as he ran over and began digging it out, and they found later that it did. Platinum is usually found in small granules, but there are records of chunks being found weighing twenty pounds while others, the size of pigeons' eggs, are not uncommon.

"Say, this is great!" yelled Ned, discovering another large piece, and digging it out.

"I am glad we could lead you to it," said the elder Russian brother. "It is a small return for what you did for us!"

"Nonsense!" cried Tom. "These must be a king's ransom here. Everybody dig it out! Get all you can."

They were all busy, but the light of the two torches Tom had brought was not sufficient for good and efficient work, so after getting several thousand dollars worth of the precious metal, they decided to postpone operations until morning, and come with more lights.

They were at the work soon after breakfast, the night in the air glider having passed without incident. The treasure of platinum proved even richer than the Russians had thought, and it was no wonder the Imperial government had tried so hard to locate it, or get on the trail of those who sought it.

"And it's all good stuff!" cried Tom eagerly. "Not like that low-grade gold of the underground city. I can make my own terms when I sell this."

For three days our friends dug and dug in that platinum mine, so many years lost to man, and when they got ready to leave they had indeed a king's ransom with them. But it was to be equally divided. Tom insisted on this, as his Russian friends had been instrumental in finding it. Toward the end of the excavation large pieces were scarce, and it was evident that the mine was what is called a "lode."

"Well, shall we go back now?" asked Tom one day, after the finish of their mining operations. The work was comparatively simple, as the platinum lumps had merely to be dug out of the sides of the cave. But the loneliness and dreariness of the place was telling on them all.

"Can't we carry any more?" asked Ned.

"We could, but it might not be safe. I don't want to take on too much weight, as my glider isn't as stable as the airship. But we have plenty of the metal.

"Indeed we have," agreed Ivan Petrofsky. "Much of mine and my brother's will go toward helping relieve the sufferings of the Siberian exiles," he added.

"And mine, too," said Alexis Borious.

They started back early the next morning in a more terrific gale than in any the glider had yet flown. But she proved herself a stanch craft, and soon they were at the place where they had left the airship. It was undisturbed.

Four days were spent in taking apart the glider and packing it on board the Falcon. Then, with the platinum safely stored away Tom, with a last look at the desolate land that had been so kind to them, sent his craft on her homeward way.

It was when they were near the city of Pirtchina, on the Obi river, that what might have proved a disastrous accident occurred. They were flying along high, and at great speed, for Tom wanted to make all the distance he could, to get out of Siberia the more quickly. They had had a fair passage so far, and were congratulating themselves that they would soon be in civilization again.

Suddenly, Mr. Damon, who had been on the after deck, taking observations through a telescope, came running forward, crying out:

"Tom! Tom! What is that water dripping from the back part of the airship?"

"Water?" exclaimed Tom. "No water is dripping from there."

"Come and look," advised Mr. Damon.

The young inventor raced back with him. He saw a thin, white stream trickling down from the lower part of the craft. Tom sniffed the air suspiciously.

"Gasolene! It's gasolene!" he cried. "We must have a leak in the supply tanks!"

He dashed toward the reserve storeroom, and at that moment, with a suddenness that was startling, the motor stopped and the Falcon lurched toward the earth.