“Dr. Trendon, are you all right?” he shouted.

“Yup,” answered a choked voice.  “Cubbing oud dow.”

Again the funnel was darkened.  A pair of feet appeared; then the surgeon’s chunky trunk, his head, and the lantern.  Once, twice, and thrice he inhaled deeply.

“Phew!” he gasped.  “Thought I was tough, but—­Phee-ee-ee-ew!”

“Did you find—­”

“No, sir.  Not Darrow.  Only a poor devil of a seal that crawled in there to die.”

The exploration continued.  Half a mile, as they estimated, from the open, they reached a narrow beach, shut off by a perpendicular wall of rock.  Skirting this, they returned on the other side, minutely examining every possible crevice.  When they again reached the light of day, they had arrived at the certain conclusion that no living man was within those walls.

“Would a corpse rise to the surface soon in waters such as these, Dr. Trendon?” asked the captain.

“Might, sir.  Might not.  No telling that.”

The captain ruminated.  Then he beat his fist on his knee.

“The other cave!”

“What other cave?” asked the surgeon.

“The cave where they killed the seals.”

“Surely!” exclaimed Trendon.  “Wait, though.  Didn’t Slade say it was between here and the point?”

“Yes.  Beyond the small beach.”

“No cave there,” declared the surgeon positively.

“There must be.  Congdon, did you see an opening anywhere in the cliff as we came along?”

“No, sir.  This is the only one, sir.”

“We’ll see about that,” said the captain, grimly.  “Head her about.  Skirt the shore as near the breakers as you safely can.”

The gig retraced its journey.

“There’s the beach, as Slade described it,” said Captain Parkinson, as they came abreast of the little reach of sand.

“And what are those two bird-roosts on it?” asked Trendon.  “See ’em?  Dead against that patch of shore-weed.”

“Bits of wreckage fixed in the sand.”

“Don’t think so, sir.  Too well matched.”

“We have no time to settle the matter now,” said the captain impatiently.  “We must find that cave, if it is to be found.”

Hovering just outside the final drag of the surf, under the skilful guidance of Congdon, the boat moved slowly along the line of beach to the line of cliff.  All was open as the day.  The blazing sun picked out each detail of jut and hollow.  Evidently the poisonous vapours from the volcano had not spread their blight here, for the face of the precipice was bright with many flowers.  So close in moved the boat that its occupants could even see butterflies fluttering above the bloom.  But that which their eager eyes sought was still denied them.  No opening offered in that smiling cliff-side.  Not by so much as would admit a terrier did the mass of rock and rubble gape.

“And Slade described the cave as big enough to ram the Wolverine into,” muttered Trendon.