In less than half an hour the motor was repaired, and was speeding the projectile on its way. It was not set at the greatest power, however, as Mr. Roumann did not want to put too much strain upon it.
"Now I have time to inquire how it happened," he said to the boys. "Tell me about it."
They related how they had come upon the crazy machinist.
"Then he has been hidden on board all the while," commented the German. "I was not mistaken in thinking some one opened that port after I closed it. He sneaked in here the night before we started, and has been waiting his chance to do us some damage. It was he who smashed the plates."
"But where could he have concealed himself?" asked Jack.
"I don't know. We'll see if he will tell us."
They went to the storeroom, where the maniac was bound.
"Why did you try to damage my machinery?" asked Mr. Roumann.
"Because it is an infringement on my patent," was the surprising answer. "I invented a perpetual motion machine, for making dog biscuits, and you have used it to make your airship go. Therefore I smashed it. I have the sole right to make dog biscuits for the king of the cannibal islands. I'm his private secretary."
"He is hopelessly insane," murmured Jack.