“That’s work for Barnett, then,” said the captain, brightening.  “We’ll blow up the whole face of the cliff, if necessary, but we’ll get at that cave.”

He hurried out.  Order followed order, and soon the gig, with the captain, Trendon, and the torpedo expert, was driving for the point marked “Seal Cave” on the map over which they were bent.

VI

MR. DARROW RECEIVES

“You say the last entry is June 7th?” asked Barnett, as the boat entered the light surf.

Trendon nodded.

“That was the night we saw the last glow, and the big burst from the volcano, wasn’t it?”

“Right.”

“The island would have been badly shaken up.”

“Not so violently but that the flag-pole stood,” said the captain.

“That’s true, sir.  But there’s been a good deal of volcanic gas going.  The man’s been penned up for four days.”

“Give the fellow a chance,” growled Trendon.  “Air may be all right in the cave.  Good water there, too.  Says so himself.  By Slade’s account he’s a pretty capable citizen when it comes to looking after himself.  Wouldn’t wonder if we’d find him fit as a fiddle.”

“There was no clue to Ives and McGuire?” asked Barnett presently.

“None.”  It was the captain who answered.

The gig grated, and the tide being high, they waded to the base of the cliff, Barnett carrying his precious explosives aloft in his arms.

“Here’s the spot,” said the captain.  “See where the water goes in through those crevices.”

“Opening at the top, too,” said Trendon.

He let out his bellow, roaring Darrow’s name.

“I doubt if you could project your voice far into a cave thus blocked,” said Captain Parkinson.  “We’ll try this.”

He drew his revolver and fired.  The men listened at the crevices of the rock.  No sound came from within.

“Your enterprise, Mr. Barnett,” said the commander, with a gesture which turned over the conduct of the affair to the torpedo expert.

Barnett examined the rocks with enthusiasm.

“Looks like moderately easy stuff,” he observed.  “See how the veins run.  You could almost blow a design to order in that.”

“Yes; but how about bringing down the whole cave?”

“Oh, of course there’s always an element of uncertainty when you’re dealing with high explosives,” admitted the expert.  “But unless I’m mistaken, we can chop this out as neat as with an axe.”

Dropping his load of cartridges carelessly upon a flat rock which projected from the water, he busied himself in a search along the face of the cliff.  Presently, with an “Ah,” of satisfaction, he climbed toward a hand’s breadth of platform where grew a patch of purple flowers.

“Throw me up a knife, somebody,” he called.

“Take notice,” said Trendon, good-naturedly, “that I’m the botanist of this expedition.”