From the pursuing aircraft came a series of sharp explosions that fairly rattled through the clear air.

"Look out for bombs!" yelled Ned.

"Bless my safety match!" cried Mr. Damon. "Are they anarchists?"

"It's only their motor hack-firing," cried Tom. "It's all right, They're done for now, well leave them behind."

He was a true prophet, for with a continued rush and a roar the airship of our friends opened up a big gap between her rear rudders and the forward planes of the craft that was chasing her. The three men were working frantically to get their motor in shape, but it was a useless task

A little later, finding that they were losing speed, the three police agents, or spies, whatever they might be, had to volplane to earth and there was no need for the Falcon to maintain the terrific pace, to which Tom had pushed her. The pursuit was over.

"Well, we got out of that luckily," remarked Ned, as he looked down to where the spies were making a landing. "I guess they won't try that trick again."

"I'm afraid they will," predicted Mr. Petrofsky. "You don't know these government agents as I do. They never give up. They'll fix their engine, and get on our trail again."

"Then we'll make them work for what they get," put in Tom, who, having set the automatic speed accelerator, had rejoined his companions. "We'll try a high flight and if they can pick up a trail in the air, and come up to us, they're good ones!"

He ran to the pilot house, and set the elevation rudder at its limit. Meanwhile the spies were working frantically over their motor, trying to get it is shape for the pursuit. But soon they realized that this was out of the question, for the Falcon was far away, every moment going higher and higher, until she was lost to sight beyond the clouds.

"I guess they'll have their own troubles now," remarked Ned. "We've seen the last of them."

"Don't be too sure," spoke the Russian. We may have them after us again. We're over the land of the Czar now, and they'll have everything their own way. They'll want to stop me at any cost."

"Do you think they suspect that we're after the platinum?" asked Tom.

"They may, for they know my brother and I were the only ones who ever located it, though unless I get in the exact neighborhood I'd have trouble myself picking it out. I remember some of the landmarks, but my brother is better at that sort of work than I am. But I think what they are mostly afraid of is that I have some designs on the life of, say one of the Grand Dukes, or some high official. But I am totally opposed to violent measures," went on Mr. Petrofsky. "I believe in a campaign of education, to gain for the down- trodden people what are their rights."

"Do you think they know you are coming to rescue your brother?" asked Tom.

"I don't believe so. And I hope not, for once they suspected that, they would remove him to some place where I never could locate him."

Calmer feelings succeeded the excitement caused by the pursuit, and our friends, speculating on the matter, came to the conclusion that the aeroplane must have started from some Prussian town, as Mr. Petrofsky said there were a number of Russian secret police in that country. The Falcon was now speeding along at a considerable height, and after running for a number of miles, sufficient to preclude the possibility that they could be picked up by the pursuing aeroplane, Tom sent his craft down, as the rarefied atmosphere made breathing difficult.

It was about three days after the chase when, having carefully studied the map and made several observations through the telescope of the Country over which they were traveling, that Ivan Petrofsky said:

"If it can be managed, Tom, I think we ought to go down about here. There is a Russian town not far away, and I know a few friends there, There is a large stretch of woodland, and the airship can be easily concealed there.

"All right," agreed the young inventor, "down we go, and I hope you get the information want."

Flying high so as to keep out of the observation of the inhabitants of the Russian town, the young inventor sent his craft in a circle about it, and, having seen a clearing in the forest, he made a landing there, the Falcon having come to rest a second time since leaving Shopton, now several thousand miles away.

"We'll hide here for a few days," observed Tom, "and you can spend as much time in town as you like, Mr. Petrofsky,"

The Russian, disguising himself by trimming his beard, and putting on a pair of dark spectacles, went to the village that afternoon.

While he was gone Tom, Ned and Mr. Damon busied themselves about the airship, making a few repairs that could not very well be done while it was in motion. As night came on, and the exile did not return, Tom began to get a little worried, and he had some notion of going to seek him, but he knew it would not be safe.

"He'll come all right," declared Ned, as they sat down to supper. All about them was an almost impenetrable forest, cut here and there by paths along which, as Mr. Petrofsky had told them, the wood cutters drove their wagons.

It was quite a surprise therefor, when, as they were leaving the table, a knock was heard on the cabin door.

"Bless my electric bell!" cried Mr. Damon. "Who can that be?"

"Mr. Petrofsky of course," answered Ned.

"He wouldn't knock--he'd walk right in," spoke Tom, as he went to the door. As he opened it he saw several dark- bearded men standing there, and in their midst Mr. Petrofsky.

For one moment our hero feared that his friend had been arrested and that the police bad come to take the rest of them into custody. But a word from the exile reassured him.

"These are some of my friends," said Mr. Petrofsky simply. "They are Nihilists which I am not, but--"

"Nihilists yes! Always!" exclaimed one who spoke English. "Death to the Czar and the Grand Dukes! Annihilation to the government!"

"Gently my friend, gently," spoke Mr. Petrofsky. "I am opposed to violence you know." And then, while his new friends gazed wonderingly at the strange craft, he led them inside. Tom and the others were hardly able to comprehend what was about to take place.