He was sure he was right, and, from calculations made, Professor Henderson was also positive. But it yet remained to prove this.

"Well, we may as well get in," said Mr. Roumann at length.

"Everything is done that can be done. The next thing is to start the motors, and--then we'll see what happens."

It was a nervous moment. Once they were in, side the great projectile, sealed up, would they ever be able to emerge again?

It was a momentous question.

"Well, here goes!" exclaimed Jack with a jerky laugh as he stepped into the Annihilator.

"I'm with You," added Mark as he followed his chum.

"Come on, Washington!" cried Jack from within.

"Wait till I take one mo' look at terra cotta!" said the colored man.

"You mean terra firma, I guess," spoke the professor.

"Yes, sah. Dat's. .h.i.t. Terra flirma--de earth. I wants t' bid it good-by."

Andy Sudds, still carrying his gun, went in next. Then followed Amos Henderson, and finally the German scientist. The latter clamped fast the cover of the opening by which they had entered.

The interior of the Annihilator was brilliant with electric lights.

Mr. Roumann made his way to the pilot house, to see that all the levers and wheels that controlled the engines were in working order. Then he went to the engine-room, where he adjusted the two motors.

"Well," he said a bit nervously, "we are all ready to start."

"Let her go!" cried Jack gaily.

There was no crowd on hand to see them off. Professor Henderson's relative was the only spectator.

Mr. Roumann and Mr. Henderson went to pilot house again. They held a brief consultation.

"Come here, boys, if you want to see us start the motors going,"

called the professor.

Jack and Mark stood in the doorway. Mr. Roumann grasped a lever.

He threw it over. There was a spark as the electrical contact was made.

"The atmospheric motor is now ready to start!" he remarked.

"Push that k.n.o.b, Professor Henderson."

The professor pushed in a small, shiny k.n.o.b. Mr. Roumann turned a small wheel, and closed another electrical switch.

Instantly there was a trembling through t whole length of the projectile. Would it move? Would it leave the earth and go to Mars?

There was a moment of hesitancy, as if the great machine had not quite decided.

Then came a more violent vibration. There was a humming, throbbing, hissing sound. Suddenly the boys, and all within the projectile, felt it swaying. A moment later it began to shoot through s.p.a.ce like a great rocket.

"Hurrah!" cried Jack. "We're off!"

"Yes," added Mr. Roumann joyfully, "we are on our way to Mars!"

and he grasped the steering wheel and peered through the thick plate-gla.s.s windows of the pilot house into the vast s.p.a.ce before them.

CHAPTER XV

SOMETHING ABOUT MARS

"Are we really in motion?" asked Jack, after a moment's silence.

"It doesn't seem so."

"We are certainly in motion," declared Mr. Roumann. "See this dial?"

He pointed to one near the steering wheel. The hand on it was gently vibrating between some of the figures.

"We are traveling that many miles a second," went on the scientist. "The atmospheric motor is not working as fast as I hoped it would, but we are going fast enough. When we start the Etherium machine we shall go much more speedily."

"And when will that be?" asked Mark.

"I can't tell exactly. It will not be until we have pa.s.sed through the atmosphere of the earth, and there is no way of ascertaining in advance just how thick that stratum is."

"Then how will you know?" asked Jack.

"By means of my instruments. When the hand on this dial points to zero I will know that we are beyond the atmosphere, and that it is time to start the Etherium motor."

"How do you know in which direction to steer?" asked Mark. "Can you see anything out of that window?"

"Not a thing," replied the German. "Look for yourself."

Jack and Mark peered through the plate gla.s.s. All they could see was a sort of white, fleecy ma.s.s of clouds that surrounded the great projectile.

"It's just like when we were above the clouds in the Electric Monarch," said Jack.

"Exactly," agreed Mr. Henderson.

"But if you can't see anything, how can you tell where to steer?"

asked Mark.

"By means of this instrument," replied Mr. Roumann, indicating another among the many on the wall of the projectile. "This is automatically kept pointed at Mars, and by means of a hand and dial I can tell how to keep the Annihilator aimed directly at the red planet."

"Even when it is on the opposite side of the earth from us?"

asked Jack.

"We are now far above the earth," was the answer, "and the planet on which we lived offers no obstruction to my telescope being pointed at Mars, even though it is daytime, when Mars is on the opposite side of the earth."