"Bless my bank book! Of course I'll go," he said. "But don't say anything about it to my wife--that is, just yet. I'll bring her around to it gradually. She has always wanted a diamond ring set in platinum, and now I can get it for her. I know she'll let me go if I break it to her gently." It may be mentioned here that many valuable diamonds are now set in platinum instead of gold. "I want to keep busy," said Mr. Damon, so Tom set him, Ned and Eradicate at the task of getting the big airship in shape for the trip. This air craft has not figured in any of my previous stories, but as it is so nearly like the one that was crushed in the caves of ice, I will not give a description of it here. Those who care to may refer to the book telling of Tom's trip to the caves of ice for a detailed account of the craft. Sufficient to say that this latest airship, named the Falcon, was the largest Tom had ever built. It contained much room, many comforts, and could sail for several thousand miles without descending, except in case of accident. It was a combined dirigible balloon 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.