As for the boys, they were only stunned, nor was Mr. Henderson more than momentarily shocked. In a few minutes the German professor was almost himself again.
"We must try to discover who our enemy is," he said earnestly, as he looked over the disabled motor. "He might have blown up the whole projectile by tampering as he did with the machinery. Had I been testing the large, instead of the small motor, there would have been nothing left of the Annihilator, or us, either. Who could have done this? If that crazy machinist is around again——"
"I don't believe he could get here from Mars," interrupted Jack, with a smile.
"Hardly," added Mark.
"No, I guess he is still on the Red Planet, so it couldn't have been him," went on Mr. Roumann. "But it was some one."
Jack and Mark at once thought of the odd man who had sent Mark the note, and then had run away.
"Could it have been him?" suggested Jack.
"It's possible," remarked Professor Henderson. "We must be on our guard. I wonder if Washington——"
At that moment there sounded a violent pounding on the exterior of the projectile, and the voice of the colored man could be heard calling:
"Am anything de mattah? Andy Sudds an' I is out heah, an' we heard suffin goin' on in dere. Am anybody hurted?"