"I'm blest if I know!" Bob replied, in a tone of perplexity. "It sounded close aboard; but how can—— Say, is there anything below which could explode?"
"Not when there's no steam on."
The old sailor stood staring at the shore in silence, evidently seriously disturbed, and the three boys gathered around him in alarm. They had experienced so much which was both mysterious and terrible since the morning of the sail in the Sally Walker, that to them every unusual sound or movement meant further disaster, and Bob's palpable fear caused something very like horror to come upon them.
Joe had mechanically started forward, and before reaching the pilot-house he shouted, to the intense relief of all:
"We were more scared than hurt this time! It was only the heaving-line. It has parted, and in doing so made the noise; but I don't understand how there could be so much strain."
Bob glanced ashore quickly, assured himself that one end of the rope was still made fast to the tree, and then cried triumphantly as he pointed astern:
"There's where the strain came from! The sun has been dryin' the hawser till it pulled the tug back far enough to break the line! That shows how much can be done by tryin'! The Sea Bird is ready to come off the shoal if we help her a bit; so turn to, lads, an' work for all you're worth till she's in deep water once more!"
The slackened hawser, which a short time previous had been so taut, told that Bob's explanation was the correct one, and there was no necessity to urge either the boys or Joe any further. To have a chance of saving the little steamer after all had firmly believed she was helplessly stranded aroused every member of the crew as nothing else, save the actual arrival of friends, could have done.