"After we get well away we can turn on the electrics," remarked Tom, "and if they see us at a distance they may take us for a meteor. But, so close as this, they'd get wise in a minute." Mr. Damon, who had done all that Tom needed in the starting of the craft, went to the forward port rail, and idly looked down on the black forest they were leaving. He could just make out the clearing where they had rested for over a week, and he was startled to see lights bobbing in it. "I say, Mr. Petrofsky!" he called. "Did we leave any of our lanterns behind us?" "I don't believe so," answered the exile. "I'll ask Tom." "Lanterns? No," answered the young inventor. "Before we started I took down the only one we had out. I'll take a look." Setting the automatic steering apparatus, he joined Mr. Damon and the Russian. The lights were now dimly visible, moving about in the forest clearing. "It's just as if they were looking for something," said Tom. "Can it be that any of your Nihilist friends, Mr. Petrofsky are--" "Friends--no friends--enemies!" cried the Russian. "I understand now! We got away just in time. Those are police agents who are looking for us! They must have received word about our being there. Androwsky and the others never carry lights when they go about. They know the country too well, and then, too, it leads to detection. No, those are police spies. A few minutes later, and we would have been discovered." "As it is we're right over their heads, and they don't know it," chuckled Tom. The airship was moving silently along before a good breeze, the propellers not having been started, and Tom let her drift for several miles, as he did not want to give the police spies a clew by the noise of the motor. The twinkling lights in the forest clearing disappeared from sight, and the seekers went on in the darkness. "Well, we've got the hardest part of our work yet ahead of us," remarked Tom several hours later when, the lights having been set aglow, they were gathered in the main cabin. There was no danger of being seen now, for they were quite high. "We've done pretty well, so far," commented Ned. "I think we will have easier work rescuing Mr. Petrofsky's brother than in locating the mine. "I don't know about that," answered the Russian. "It is almost impossible to rescue a person from Siberia. Of course it is not going to be easy to locate the lost mine, but as for that we can keep on searching, that is if the air glider works, but there are so many forces to fight against in rescuing a prisoner." They had a long journey ahead of them, and not an easy route to follow, but as the days passed, and they came nearer and nearer to their goal, they became more and more eager. They were passing over a desolate country, for they avoided the vicinity of large towns and cities. "I wonder when we'll strike Siberia?" mused Tom one afternoon, as they sat on the outer deck, enjoying the air.