"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 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.