They came down in a big field, and, almost before the bicycle wheels had ceased revolving, under the application of the brakes, several men came running toward them. "Here they come!" cried Mr. Damon. "They are only farmers," said the exile. He had donned his dark glasses again, and looked like anything but a Russian. "Lively, Ned!" cried Tom. "Let's see if we can't make repairs and get off again." The two lads frantically began work, and they soon had the magneto in running order. They could have gone up as an aeroplane, leaving the repairs to the gas bag to be made later but, just as they were ready to start, there came galloping out a troop of Cossack soldiers. Their commander called something to them. "What is he saying?" cried Tom to Mr. Petrofsky. "He is telling them to surround us so that we can not get a running start, such as we need to go up. Evidently he understands aeroplanes." "Well, I'm going to have a try," declared the young inventor. He jumped to the pilot house, yelling to Ned to start the motor, but it was too late. They were hemmed in by a cordon of cavalry, and it would have been madness to have rushed the Falcon into them, for she would have been wrecked, even if Tom could have succeeded in sending her through the lines. "I guess it's all up with us," groaned Ned. And it seemed to; for, a moment later, an officer and several aides galloped forward, calling out something in Russian. "What is it?" asked Tom. "He says we are under arrest," translated the exile. "What for?" demanded the young inventor. Ivan Petrofsky shrugged his shoulders. "It is of little use to ask--now," he answered. "It may be we have violated some local law, and can pay a fine and go, or we may be taken for just what we are, or foreign spies, which we are not. It is best to keep quiet, and go with them." "Go where?" cried Tom. "To prison, I suppose," answered the exile. "Keep quiet, and leave it to me. I will do all I can. I don't believe they will recognize me. "Bless my search warrant!" cried Mr. Damon. "In a Russian prison! That is terrible!" A few minutes later, expostulations having been useless, our friends were led away between guards who carried ugly looking rifles, and who looked more ugly and menacing themselves. Then the doors of the Russian prison of Owbinsk closed on Tom and his friends, while their airship was left at the mercy of their enemies. CHAPTER XIX LOST IN A SALT MINE The blow had descended so suddenly that it was paralyzing. Tom and his friends did not know what to do, but they saw the wisdom of the course of leaving everything to Ivan Petrofsky. He was a Russian, and he knew the Russian police ways--to his sorrow.