"I'd pay a reward out of my own pocket for the right answer," Reade replied.
"Then you haven't a theory?" asked the treasurer.
"Not even an imitation of a theory," Tom laughed, shortly.
All this time the motor boat was gliding out toward the scene of the wreck.
"Now, you can see the damage that has been done," suggested Mr. Corbett, turning the light fully on the scene of the latest blow-out. "You see, a long strip of the wall has been cleaned out. Not a trace of the damaged part shows above water."
"It wasn't as big an explosion as the other two, though," Reade declared. "Really, it looks as though the folks behind this found themselves running low on explosives."
"There must be a trace or a clue left," urged Mr. Prenter.
"High explosives don't leave many traces of anything with which they come in contact," muttered Harry. "If we do find any traces, I guess it will have to be in broad daylight."
"And I guess that's right," agreed Tom. "Mr. Corbett, did none of your men patrolling on the wall report any signs of strangers?"
"No such report was made, sir."