The captain said he had a fair quantity of powder on board, to be used in the cannon for saluting and signalling.  If they wanted dynamite, however, he’d have to run over to one of the big islands for it.

“And then we may have trouble getting it,” he added.  “We’d probably have to buy up the supply of some contractor who happened to have it on hand.”

“I don’t like to think of leaving the island while Merrick and his crowd are around,” answered Anderson Rover.

On the following morning Mr. Rover and Captain Barforth went ashore, taking Dick, Tom and Sam along.  The steam yacht was left in charge of Asa Carey, and the mate was told to remain close to the mouth of the reef and to send some of the others ashore armed if there came a signal of distress.

“We have enemies on this isle,” said Captain Barforth.  “And they may try to do us harm.”

“I’ll watch out,” answered the mate, shortly.  And then he turned away with a thoughtful look on his sour countenance.  That there was something on his mind was evident.

The small boat was brought ashore at the point where the path led directly to the sunken cave.  Although there was a lively breeze blowing, those landing did so without mishap.  They had with them some tools for digging, and also a rock drill and some powder.

“It will do no harm to blast one or two of the rocks and see what is underneath,” said Anderson Rover.  “We may possibly be lucky enough to find some entrance into the cave, although I must confess I doubt it.”

When they got to the vicinity of the shattered cave they found everything as they had left it.  Even a pick Tom had forgotten remained undisturbed.

“Evidently the Merrick crowd has not yet found its way here,” said Dick.

“We shall have to be on our guard when we go to blasting,” answered his parent.  “For the noise may bring that rascal and his gang here in a hurry.”

And then all set to work with vigor to see if by some means they could not get down under the rocks and to the spot where the precious treasure had been deposited so many years before.

CHAPTER XXVII

WHAT HAPPENED ON THE STEAM YACHT

About an hour after the Rovers and Captain Barforth had left the steam yacht Dora came from the forward deck looking much disturbed.

“What is the trouble?” asked her mother.

“Oh, not very much,” she answered, for she did not wish to worry her parent.  “Where is Fred?”

“I think he is at the stern, fishing with Hans and John.”

“I want to see them,” continued Dora, and hurried off.

She found the three chums at the stern.  They had been fishing for some time and several fish lay on the deck near them.

“Hullo, Dora, want to try your luck?” asked Fred, pleasantly.  “I’ll fix you a line—­and fix lines for Nellie and Grace, too, if they want them.”