Hold on!  Perhaps—­just perhaps—­it may be read.  The officer was not long dead.  Ensigns of the U. S. navy do not wander about untraversed waters alone.  There must be a warship somewhere in the vicinity.  But why, then, an unburied officer floating on the ocean?  I will smoke upon this, luxuriously and plentifully. (Later.) No use.  I can’t solve it.  But one thing I do.  I put up a signal pole on the headland and cache this record under it this afternoon.  From day to day, with the kindly permission of the volcano, I will add to it....  Bad doings by Old Spitfire.  The cloud is coming down on me.  Also seems to be moving along the cliff.  I will retire hastily to my private estate in the cave_.

“That’s all, except the scrawl on the last page,” said Trendon.  “Some action of the volcano scared him off.  He just had time to scrawl that last message and drop the book into the cache.  The question is, did he get back alive?”

“I doubt it,” said the captain.  “We will search the headland for his body.”

“But the cave,” insisted the surgeon.  “We ought to have found some sign of him there.”

“Slade is the solution,” said the captain.  “We must ask him.”

They put back to the ship.  Barnett was anxiously awaiting them.

“Your patient has been in a bad way, Dr. Trendon,” he said.

“What’s wrong?” asked Trendon, frowning.

“He came up on deck, wild-eyed and staggering.  There was a sheet of paper in his hand which seemed to have some bearing on his trouble.  When he found you had gone to the island without him he began to rage like a maniac.  I had to have him carried down by force.  In the rumpus the paper disappeared.  I assumed the responsibility of giving him an opiate.”

“Quite right,” approved Trendon.  “I’ll go down.  Will you come with me, sir?” he said to the captain.

They found Slade in profound slumber.

“Won’t do to wake him now,” growled Trendon.  “Hello, what’s here?”

Lying in the hollow of the sick man’s right hand, where it had been crushed to a ball, was a crumpled mass of tracing paper.  Trendon smoothed it out, peered at it and passed it to the captain.

“It’s a sketch of an Indian arrow-head,” he exclaimed in surprise, at the first glance.  “What are all these marks?”

“Map of the island,” barked Trendon.  “Look here.”

The drawing was a fairly careful one, showing such geographical points as had been of concern to the two-year inhabitants.  There was the large cavern, indicated as they had found it, and at a point between it and the headland the legend, “Seal Cave.”

“But it’s wrong,” cried Captain Parkinson, setting finger to the spot.  “We passed there twice.  There’s no opening.”

“No guarantee that there may not have been,” returned the other.  “This island has been considerably shaken up lately.  Entrance may have been closed by a landslide down the cliff.  Noticed signs myself, but didn’t think of it in connection with the cave.”