"We must set watches to-night, I suppose?" asked Andy.
"Certainly! Although these people are supposed to be our friends, we must imagine ourselves in hostile waters. I remember once that a small schooner put into Niihau. The natives came off to barter, and appeared to be extremely friendly. During the night about a couple of hundred swam off to the schooner and took her crew entirely by surprise. We found the charred remains of her timbers about a month afterwards, but not a trace of her unfortunate crew. They had been made into 'big pig.'"
"The usual. Gunboat, landing party, etc. The village was shelled and burnt, and the island afterwards annexed to the Empire. So, you see, we must exercise due caution, although I don't want to upset your nerves."
It must have been shortly after midnight when the crew was awakened by a warning shout from Terence. Turning out of their comfortable bunks, the others rushed from the cabin, armed in anticipation of a sudden and treacherous attack.
A low rumbling greeted their ears, the sound apparently coming from the shore. For more than a minute the mysterious sound continued, then it suddenly ceased.
"I'm afraid I cannot tell you," replied his father. "It's rather like the sound of a submarine explosion; probably a volcanic eruption."
Again the noise was repeated, yet no agitation of the placid water took place. The natives did not appear to be disturbed, for no commotion due to human agency could be heard from the island. This time the rumbling continued for quite five minutes, dying away in a succession of long-drawn tremors. Then all was quiet.
"I can't make it out," remarked Mr. McKay. "Whatever it is it seems to be accepted by the natives without a protest. To-morrow I'll inquire."
The party remained on deck for nearly an hour, but as the mysterious noise was not repeated, they at length retired to the cabin, leaving Terence to continue the remainder of his watch.
Just after sunrise Ellerton called Mr. McKay's attention to something on the beach. Seizing his glasses, the elder man brought them to bear upon the spot, and the next moment he exclaimed:
"Come on, lads, get your arms and row ashore as hard as you can."
Without waiting for an explanation, the three lads jumped into the boat, Mr. McKay taking his place in the stern sheets.