"Hu! Den I 'spects I'se got t' go," said the colored man, scratching his head in perplexity. "I can't let de perfesser go alone, wid n.o.body t' do his cookin' fer him. Well, I'll go, but--but I'se mighty skeered, jest de same."

"You needn't be, Washington," said Mr. Henderson kindly. "We will be perfectly safe in the Annihilator, and when we get to Mars I am sure you will like it there."

"I've got to, wedder I does or not," said Washington simply.

"Well, t' t'ink ob me seein' dis work goin' on, day after day, an' me nebber suspectin' dat yo' was goin' on sech a transmigatory flight in de direction ob an interplanetary sphere what transmits effulgent rays transversely an' pyritiferilously changes 'em inter crimson light most advantageously."

"I guess you're all right now, after getting that out of your system," observed Mark.

It was two days after this that Jack and Mark, who were working in the shop with Mr. Roumann, suddenly heard him utter a cry.

"Has anything happened?" called Jack, dropping his tools and hastening to the engine-room, where the scientist was.

"Yes!" cried the German.

"What?"

He was pacing rapidly up and down the contracted s.p.a.ce, waving a piece of metal above his head. Jack thought he might have hurt himself.

"I have discovered what was the matter with my Etherium motor!"

exclaimed Mr. Roumann. "I didn't bend this piece of metal properly. That was why the machine did not work satisfactorily.

Now it is all right. We can start in a week."

"That's good!" said Mark, who had joined his chum. "Are you sure it will work now, Mr. Roumann?"

"Quite sure. But we will have a test to make certain. Send Professor Henderson here, Please."

The other scientist came from the house, and the test was made.

To the delight of all the Etherium motor worked perfectly. The slight adjustment of the piece of metal had been all that was needed.

"Now we can get ready to leave in a week," repeated the German enthusiastically.

In fact, the projectile was finished, and all that was necessary was to put in the stores and some supplies, turn on the power, and they would be off through s.p.a.ce.

The actual starting of the Annihilator was, of course, to be left entirely to Mr. Roumann. He had not disclosed to his companions the secret of the force that was to make it move, nor had he told them how to work the Etherium and atmospheric motors. He would start the machinery in operation, and he had promised to show the professor and the boys how to control it, but the secret of the wonderful power he kept to himself.

"I think we can let the two machinists go now," said Mr. Henderson at the conclusion of the tests. "We shall not need them any more if we are almost ready to start."

"No, we can dispense with their services," agreed Mr. Roumann; and, accordingly, Ned and Sam were paid off, and left, promising to say nothing of the wonderful apparatus on which they had been working.

The next week was a busy one. Mr. Roumann spent most of his time in the engine-room, a.s.sembling the machinery of the two motors, and arranging the connections between them and the pilot house in the "nose" of the projectile. The strange gas had been forced in between the two sh.e.l.ls of the projectile, to absorb the heat that would be generated by friction, and nearly all the stores had been put aboard.

The electric guns were installed, ready to be run out of the openings of the living-room to repel any attack of the Martians, and then the ports were closed tightly.

Finishing touches were being put on the Annihilator, and Mr.

Henderson and his German friend were kept very busy. As for the boys, they helped wherever they could, and did considerable work, for they had been well trained by their guardian.

Andy remained on guard at the door with his gun. He said he was going to take no more chances with the crazy machinist.

Nothing further had been seen or heard of the mysterious thief who had stolen the plates, and it was supposed that he was unable to make any use of them.

One afternoon, about three days before the time set to start for Mars, Mr. Roumann was working alone in the machine shop. The boys and Professor Henderson had done all there was for them to do, and the Annihilator was practically finished.

"Are you going to take along any extra-sized bullets, Andy?"

asked Jack of the old hunter, who was on guard, as usual, at the door.

"I don't see why I should. I guess the regular ones will do when I get to Mars."

"I don't know about that," went on Jack. "We may find bigger game than elephants or sea lions there."

"If we do, I'll use a new kind of explosive electric bullet Mr.

Roumann told me about," declared Andy. "It has a charge of electricity in it, and he says it will kill the biggest animal that ever lived, with one shot."

"Then you're all right," said Mark. "Well we'll soon be on our way now."

"I suppose Washington will want to take some of his chickens along?" ventured Jack.

"Well, I don't see why he can't," said Andy. "They take pigeons up in balloons, and I guess chickens would live in the Annihilator--at least, until we ate them."

They stood about the entrance to the machine shop, talking of various topics, but they always came back to the subject of the wonderful journey before them.

Suddenly Jack, who had strolled a little away from the door, looked toward the rear of the big shed that housed the projectile, and uttered a cry. Mark heard him, and ran to his chum's side.

"Look!" exclaimed Jack, pointing to two men who were running away from the shop. "Who are those men?"

"One is that crazy machinist!" cried Mark.

"And the other is the tramp we saw looking in the window that night!" added Jack. "Come on! Let's catch them! They may have done some damage! Andy! Here! With your gun! Quick!"

The old hunter hastened to join the boys. He reached them in time to see the two intruders making for the woods back of the shed.

"Hold on there!" cried Andy, quickly raising his gun and firing over their heads.

But the men did not stop. Hardly had the echoes of Andy's weapon died away, than there sounded a loud explosion from the shop. A cloud of smoke poured from the windows.

"They've blown up the projectile!" cried Mark. "Come on!"

They ran toward the place where the explosion had occurred. As they neared the end of the shed Washington came running out. He showed great fear.

"Come quick! Come quick!" he cried.

"What's the matter?" shouted Jack.

"Somebody's blowed de place up, an' Mr. Roumann am killed!" was the answer.

CHAPTER XII