"Hark!" exclaimed Jack suddenly.
There was good reason for his exclamation. Even at the depth at which they were located, they could hear the sounds of firing, as the furious volleys, of which we know, were leveled at the submarine.
"Something's going on up above," decided Sam Hartley. "Wonder what can be up?"
"Maybe those rascals are quarreling among themselves," said Jack.
"Let's go back and enter the light-house through the trap-door," suggested Sandy.
But Sam Hartley shook his head.
"I know a better way than that," he said. "You notice that this cell, in which I have been confined, is merely a section of the tunnel closed in?"
The boys nodded.
"You opened the door by which my jailers brought me food when you slid that outside bolt," he said; "but at this other end there's a kind of a bulkhead. I succeeded in working it somewhat loose, but my failing strength would not permit my proceeding with the job. But through cracks in it I've smelled fresh air. I'm sure it opens out of doors. What do you say if we try to force it by our united efforts?"
The bulkhead referred to by Sam Hartley was an affair of boards and what seemed to be driftwood, held together by iron braces. As he had said, it was in a shaky condition.