"Just sneaking along the window here as if listening."

"Maybe he was trying to hear what we were talking about,"

suggested Jack.

"Or trying to discover my secret," added Mr. Roumann quickly.

"Fortunately I never talk about the secret of the power. But I shall be anxious about the machine shop."

"Suppose we go out and take a look around it," proposed Mark.

"Ned and Sam will know if any intruder has been sneaking around there."

They all went out where the Annihilator was in process of building, but the machinists said they had not been disturbed, and they were sure no one had stolen anything.

There was no further disturbance that night, but when Mr. Roumann paid an early visit to the machine shop the next morning, he uttered a cry of surprise.

"What is it?" asked Jack, who accompanied him.

"The plates--the plates of the Etherium motor!" cried the scientist. "They have been stolen!"

CHAPTER IX

A CRAZY MACHINIST

For a moment Jack stared at Mr. Roumann. He did not appreciate the seriousness of the announcement. The scientist was hurrying here and there, looking under benches and on tables for missing plates.

"Do you mean the plates that make the motor go?" asked Jack.

"No, not those, but the plates from which the mysterious force is projected into s.p.a.ce--the plates that give the forward motion to the projectile. They have been stolen. They were taken last night, and the man Andy fired at stole them!"

"Will that prevent us from making the trip?"

"No. I have duplicate plates."

"Then little harm is done."

"No particular harm is done to the projectile, but I am afraid that, with the plates in his possession, the man may discover the secret of the power that I use. Oh, I should have locked them up, but I thought they would be safe."

"What has happened?" asked Mr. Henderson, entering the machine shop at that moment. The scientist told him, and expressed his fear.

"Do you really think there is any danger that the man, whoever he was, will learn how to use the plates?" inquired the professor.

"Perhaps, and then, again, perhaps not. I think it will be very difficult for him to work out the secret of the power from the plates, for they are only a small part of the mechanism. Still, he may do so. I am convinced now that this man is either the same one of whom I stand in fear, or he is some one hired by him to steal my secret."

"Then we had better notify the police," suggested Mark.

"No, that would never do," answered Mr. Roumann. "I would have to describe the plates, in order to have the authorities identify them in the possession of the thief, and I do not care to do that. No; the best plan will be to hasten work or the Annihilator, and start for Mars before the thief can gain any advantage from the plates. If he should succeed in discovering from the plate how to make the power that is discharged in wireless currents, it will take him a long time, and we can be away before then. Let us hasten our work and start for Mars."

"You say you have duplicates of the plates?" asked Jack.

"Yes. I was afraid lest something happen to one set, so I made three. Well, it will do no good to worry, but I wish I had the plates back."

"I don't see how he got them," observed Mark. "There doesn't seem to be anything broken, to indicate how the thief got in, and he certainly didn't touch Professor Henderson's live wire."

Not a window or a door had been forced, and the two machinists, who slept in the shop, declared they had heard no suspicious sounds during the night. It was a mysterious theft, and there seemed to be no means of solving it.

At Mr. Roumann's suggestion they all increased their hours of work on the Annihilator. They wanted to have it finished ahead of the time set, and it seemed that this would be done.

Day after day, and far into the night, they labored. Bit by bit the machinery was installed, the supplies were gathered together, the great water tanks were built, to provide a supply of the fluid in case of any accident to the distilling apparatus. The Etherium motor was almost finished, and the other, motor, which was to drive the Annihilator through the earth's atmosphere, was nearly ready to install. The steering apparatus necessitated considerable labor, and when it was finished Amos Henderson declared they had made a mistake, and would have to build it all over again.

This lost them a week, and time was precious, as there was no telling what the thief would do with the stolen plates.

"I tell you what, but we're going to have a better ship than any of the others we built," remarked Jack one day, as he and Mark were putting the finishing touches to the living-room.

"This isn't a ship," said Mark. "It's a projectile."

"I guess I can call it a ship if I want to," was the retort.

"It's going to sail through the air, and it's an airship, of course. Wait until you see the one I'm going to build when I get that new gas invented."

"I'll not go with you," said Mark. "There's too much danger of being blown up."

"There won't be, after I have it perfected. But say, won't it be fine when we're shooting through s.p.a.ce to sit here in an easy chair and read a book and eat sandwiches?"

"I guess you think as much of eating as you do of reading, Jack."

"Well, almost, that's a fact. I must cut out some of my eating, too. I've gained five pounds this week, because of not doing any studying. But wait until I get to Mars. Then I'll weigh less."

"I hope Mr. Roumann lets us help run the machinery," went on Mark.

"I guess he'll have to. He'll need help, and I understand that he and the professor, you and I, and Washington and Andy are the only ones going along. He and the professor can't run the affair all alone, and they'll have to have our help. Wash and Andy won't be much good at machinery."

"That's so. My! Think of steering a two hundred-foot projectile through s.p.a.ce, when we're moving at the rate of one hundred miles a second!"

"Great, isn't it?" commented Jack.

"It would be a bad thing if it ever got away from us," said Mark.

"Yes; or if we steered into a comet."

"That's so. We may run into one of those things--or a shooting star."

"As long as we don't fall into the sun and get burned up we'll be all right," went on Jack. "And when we get to Mars I know what I'm going to do."

"What?"

"Go for a sail on one of the big ca.n.a.ls. Mars is covered with them, astronomers say."