Jack was pulling the steel portal toward him. An eager face, peering from a port, waited anxiously for the tremor which would indicate that the projectile had left the earth. In another moment they would be off.
But what was that sound coming from down the highway. A steady chug-chug—a sort of roar, as of a battery of rapid-fire guns going off in double relays! And, mingled with the explosions, there was a voice shouting:
"Wait! Hold on! Don't go without me! I'm Mark Sampson! Don't start the projectile!"
"Somebody must be in a mighty hurry on a motorcycle," thought Jack, as he paused a moment before fastening the door. Then the shouts came to his ears.
"Mark Sampson!" he cried.
Again came the cry: "Wait! Wait! Don't go without me! You've got that mysterious man on board!"
"Mark Sampson!" murmured Jack again. "That's his voice sure enough! I wonder—can it be possible—that man—with his head all bandaged up—his queer actions—I—I——"
Words failed the youth. Throwing wide open the door, he sprang out of the projectile. A moment later there dashed into the yard, where the great projectile rested, a strange figure astride of a puffing motorcycle. The figure was torn and, ragged, and the nondescript garments were covered with dust, for Mark had had a fall. But there was no mistaking the face that peered eagerly forward.
"Jack!" cried the youth on the machine.
"Mark!" ejaculated the lad who had sprung from the projectile. "What has happened? Who is the fellow who has been masquerading as you?"