Rapidly the airship ascended, and, when it was high over the town of Shopton, Tom headed the craft due west. Looking down he tried to descry Mary Nestor, in her carriage, but the trees were in the way, their interlocking branches hiding the girl. Tom did see crowds of other persons, though, thronging the streets of Shopton, for, though the young inventor had made many flights, there was always a novelty about them, that brought out the curious.

"A good start, Tom Swift," complimented Mr. Parker. "Is it always as easy as this?"

"Starting always is," was the answer, "though, as the Irishman said, coming down isn't sometimes quite so comfortable."

"Bless my gizzard! That's so," cried the eccentric Mr. Damon. "Can we vol-plane to earth in the Red Cloud, Tom?"

"Yes, but not as easily as in the Butterfly. However I hope we will not have to. Now, Mr. Damon, if you will just take charge of the steering apparatus for a minute, I want to go aft."

"What for?"

"I wish to see if everything is all right. I can't imagine why Eradicate was making those queer motions."

Mr. Damon, who knew how to operate the Red Cloud, was soon guiding her on the course, while Tom made his way to the rear compartments, through the motor room, where the stores of supplies and food were kept. He made a careful examination, looking from an after window, and even going out on a small, open platform, but could discover nothing wrong.

"I guess Rad was just capering about without any special object," mused Tom, but it was not long after this that they learned to their dismay, that the colored man had had a method in his madness.

On his way back through the motor room Tom looked to the machinery, and adjusted some of the auxiliary oil feeders. The various pieces of apparatus were working well, though the engine had not yet been speeded up to its limit. Tom wanted it to "warm- up" first.

"Everything all right?" asked Mr. Damon, as Tom rejoined them in the pilot house, which was just forward of the living room in the main cabin.

"Yes, I can't imagine what made Rad act that way. But I'll set the automatic steering gear now, Mr. Damon, and then you will be relieved."

Mr. Jenks was gazing off toward the west--to where he hoped to discover the secret of Phantom Mountain.

"How do you like it?" asked Tom.

"It's great," replied the diamond man. "I've never been in an airship before, and it's different than what I expected; but it's great! It's the only craft that will serve our purpose among the towering mountain peaks, where the diamond makers are hidden. I hope we can find them."

In a little while the Red Cloud was skimming along at faster speed, guided by the automatic rudders, so that no one was needed in the pilot house, since there was no danger of collisions. Airships are not quite numerous enough for that, yet, though they may soon become so.

Tom and the others devoted several hours to arranging their staterooms and bunks, and getting their clothing stowed away, and when this was done Mr. Parker and Mr. Jenks sat gazing off into space.

"It's hard to realize that we are really in an airship," observed the diamond man. "At first I thought I would be frightened, but I'm not a bit. It doesn't seem as if anything could happen."

"Something is likely to happen soon," said Mr. Parker, suddenly, as he gazed at some weather instruments on the cabin wall.

"Bless my soul! Don't say that!" cried Mr. Damon. "What is it?"

"I think, from my observations, that we will soon have a hurricane," said the scientific man. "There is every indication of it"'; and he seemed quite delighted at the prospect of his prediction coming true.

"A hurricane!" cried Mr. Damon. "I hope it isn't like the one that blew us to Earthquake Island."

"Oh, I think there will be no danger," spoke Tom. "If it comes on to blow we will ascend or descend out of the path of the storm. This craft is not like the ill-fated Whizzer. I can more easily handle the Red Cloud; even in a bad storm."

"I'm glad to hear that," remarked Mr. Jenks. "It would be too bad to be wrecked before we got to Phantom Mountain."

"Well, I predict that we will have a bad storm," insisted Mr. Parker, and Tom could not help wishing that the scientist would keep his gloomy forebodings to himself.

However the storm had not developed up to noon, when Tom, with Mr. Damon's help, served a fine meal in the dining-room. In the afternoon the speed of the ship was increased, and by night they had covered several hundred miles. Through the darkness the Red Cloud kept on, making good time. Tom got up, occasionally, to look to the machinery, but it was all automatically controlled, and an alarm bell would sound in his stateroom when anything went wrong.

"Bless my napkin!" exclaimed Mr. Damon the next morning, as they sat down to a breakfast of fruit, ham and eggs and fragrant coffee, "this is living as well as in a hotel, and yet we are-- how far are we above the earth, Tom?" he asked, turning to the young inventor.

"About two miles now. I just sent her up, as I thought I detected that storm Mr. Parker spoke of."

"I told you it would come," declared the scientist, and there was a small hurricane below them that morning, but only the lower edge of it caught the Red Cloud, and when Tom sent her up still higher she found a comparatively quiet zone, where she slid along at good speed.

That afternoon Tom busied himself about some wires and a number of complicated pieces of apparatus which were in one corner of the main cabin.

"What are you doing now?" asked Mr. Jenks, who had been talking with Mr. Parker, and showing that scientist some of the manufactured diamonds.

"Getting our wireless apparatus in shape," answered the lad. "I should have done it before, but I had so much to do that I couldn't get at it. I'm going to send off some messages. Dad will want to know how we are doing."

As he worked away, he also made up his mind to send another message, in care of his father, for there was a receiving station in the Swift home. And to whom this message was addressed Tom did not say, but we fancy some of our readers can guess.

Finally, after several hours of work, the wireless was in shape to send and receive messages. Tom pulled over the lever, and a crackling sound was heard, as the electricity leaped from the transmitters into space. Then he clamped the receiver on his ear.

"All ready," he announced. "Has anybody any messages they wish sent?" For, with the courtesy of a true host he was ready to serve his guests before he forwarded his own wireless notes.

"Just tell my wife that I'm enjoying myself," requested Mr. Damon. "Bless my footstool! But this is great! We're off the earth yet, connected with it."

Mr. Jenks had no one to whom he wanted to send any word, but Mr. Parker wish to wire to a fellow scientist the result of some observations made in the upper air.

Tom noted all the messages down, and then, when all was in readiness he began to call his home station. He knew that either his father or Mr. Jackson, the engineer, could receive the wireless.

But, no sooner had the young inventor sent off the first few dots and dashes representing "S. I."--his home station call--than he started and a look of surprise came over his face.

"They're calling us!" he exclaimed.

"Who is?" asked Mr. Jenks.

"My house--my father. He--he's been trying to get us ever since we started, but I didn't have the wireless in shape to receive messages. Oh, I hope it's not too late!"

"Too late! Bless my soul, too late for what?" gasped Mr. Damon, somewhat alarmed by Tom's manner.

The lad did not answer at once. He was intently listening to a series of dots and dashes that clicked in the telephone receiver clamped to his left ear. On his face there was a look of worriment.

"Father has just sent me a message," he said. "It's a warning flashed through space! He's been trying to get it to me since yesterday!"

"What is it?" asked Mr. Jenks, rising from his seat.

"The mysterious man is aboard the airship--hidden away!" cried Tom. "That's what Eradicate was trying to call to our attention as we started off. Eradicate saw his face at a rear window, and tried to warn us! The mysterious man is a stowaway on board!"