Tom had the choice of two routes in making his voyage to far-off Siberia. He could have crossed the United States, sailed over the Pacific ocean, and approached the land of the Czar from the western coast above Manchuria. But he preferred to take the Atlantic route, crossing Europe, and so sailing over Russia proper to get to his destination. There were several reasons for this.

The water voyage was somewhat shorter, and this was an important consideration when there was no telling when he might have an accident that would compel him to descend. On the Atlantic he knew there would be more ships to render assistance if it was needed, although he hoped he would not have to ask for it.

"Then, too," he said to Ned, when they were discussing the matter, "we will have a chance to see some civilized countries if we cross Europe, and we may land near Paris."

"Paris!" cried Ned. "What for?"

"To renew our supply of gasolene, for one thing," replied the young inventor. "Not that we will be out when we arrive, but if we take on more there we may not have to get any in Russia. Besides, they have a very good quality in France, so all told, I think the route over Europe to be the best."

Ned agreed with him, and so did Mr. Petrofsky. As for Mr. Damon, he was so busy getting his sleeping room in order, and blessing everything he could think of, that he did not have time to talk much. So the eastern route was decided on, and as the big airship, carrying our friends, their supplies, and the wonderful air glider rose higher and higher, Tom gradually brought her around so that the pointed nose of the gas bag aimed straight across the Atlantic.

They were over the ocean on the second day out, for Tom did not push the craft to her limit of speed, now they had time to consider matters at their leisure, for they had been rather hurried on leaving.

The machinery was working as nearly to perfection as it could be brought, and Tom, after finding out that his craft would answer equally well as a dirigible balloon or an aeroplane, let it sail along as the latter.

"For," he said, "we have a long trip ahead of us "and we need to save all the elevating gas we can save. If worst comes to worst, and we can't navigate as an aeroplane any more, we can even drift along as a dirigible. But while we have the gasolene we might as well make speed and be an aeroplane."

The others agreed with him, and so it was arranged. Tom, when he had seen to it that his craft was working well, let Ned take charge and devoted himself to seeing that all the stores and supplies were in order for quick use.

Of course, until they were nearer the land of the Czar, and that part of Siberia where Mr. Petrofsky's brother was held as an exile, they could do little save make themselves as comfortable as possible in the airship. And this was not hard to do.

Naturally, in a craft that had to carry a heavy load, and lift itself into the air, as well as propel itself along, not many things could be taken. Every ounce counted. Still our friends were not without their comforts. There was a well stocked kitchen, and Mr. Damon insisted on installing himself as cook. This had been Eradicate's work but the eccentric man knew how to do almost everything from making soup to roasting a chicken, and he liked it. So he was allowed free run of the galley.

Tom and Ned spent much time in the steering tower or engine room, for, though all of the machinery was automatic, there was need of almost constant attention, though there was an arrangement whereby in case of emergency, the airship would steer herself in any set direction for a certain number of hours.

There were ample sleeping quarters for six persons, a living room and a dining saloon. In short the Falcon was much like Tom's Red Cloud, only bigger and better. There was even a phonograph on board so that music, songs, and recitations could be enjoyed.

"Bless my napkin! but this is great!" exclaimed Mr. Damon, about noon of the second day, when they had just finished dinner and looked down through the glass windows in the bottom of the cabin at the rolling ocean below them. "I don't believe many persons have such opportunities as we have."

"I'm sure they do not," added Mr. Petrofsky. "I can hardly think it true, that I am on my way back to Siberia to rescue my dear brother."

"And such good weather as we're having," spoke Ned. "I'm glad we didn't start off in a storm, for I don't exactly like them when we're over the water."

"We may get one yet," said Tom. "I don't just like the way the barometer is acting. It's falling pretty fast."

"Bless my mercury tube!" cried Mr. Damon. "I hope we have no bad luck on this trip."

"Oh, we can't help a storm or two," answered Tom. "I guess it won't do any harm to prepare for it."

So everything was made snug, and movable articles on the small exposed deck of the airship were lashed fast. Then, as night settled down, our friends gathered about in the cheerful cabin, in the light of the electric lamps, and talked of what lay before them.

As Mr. Damon could steer as well as Tom or Ned, he shared in the night watch. But Mr. Petrofsky was not expert enough to accept this responsibility.

It was when Mr. Damon finished his watch at midnight, and called Tom, that he remarked.

"Bless my umbrella, Tom. But I don't like the looks of the weather."

"Why, what's it doing?"

"It isn't doing anything, but it's clouding up and the barometer is going down."

"I was afraid we were in for it," answered the young inventor. "Well, we'll have to take what comes."

The airship plunged on her way, while her young pilot looked at the various gages, noting that to hold her way against the wind that had risen he would have to increase the speed of the motor.

"I don't like it," murmured Tom, "I don't like it," and he shook his head dubiously.

With a suddenness that was almost terrifying, the storm broke over the ocean about three o'clock that morning. There was a terrific clap of thunder, a flash of lighting, and a deluge of rain that fairly made the staunch Falcon stagger, high in the air as she was.

"Come on, Ned!" cried Tom, as he pressed the electric alarm bell connected with his chum's berth. "I need you, and Mr. Damon, too."

"What's the matter?" cried Ned, awakened suddenly from a sound sleep.

"We're in a bad storm," answered Tom, "and I'll have to have help. We need more gas, to try and rise above it."

"Bless my hanging lamp!" cried Mr. Damon, "I hope nothing happens!"

And he jumped from his berth as the Falcon plunged and staggered through the storm that was lashing the ocean below her into white billow of foam.