VI

THE CAVE WITH TWO MOUTHS

Obscure as were the directions which Hopperdown’s niece had taken from his dying lips, one point at least was clear—­the treasure-cave opened on the sea.  This seemed an immense simplification of the problem, until you discovered that the great wall of cliffs was honeycombed with fissures.  The limestone rock of which the island was composed was porous as a sponge.  You could stand on the edge of the cliffs and watch the green water slide in and out of unseen caverns at your feet, and hear the sullen thunder of the waves that broke far in under the land.

One of the boats which had conveyed us from the Rufus Smith had been left with us, and in it Mr. Shaw, with the Honorable Cuthbert and Captain Magnus, made a preliminary voyage of discovery.  This yielded the information above set down, plus, however, the thrilling and significant fact that a cave seemingly predestined to be the hiding-place of treasure, and moreover a cave with the specified two openings, ran under the point which protected the anchorage on the south, connecting the cove with the sea.

Although in their survey of the coast the voyagers had covered only a little distance on either side of the entrance to the bay, the discovery of this great double-doored sea-chamber under the point turned all thoughts from further explorations.  Only the Scotchman remained exasperatingly calm and declined to admit that the treasure was as good as found.  He refused to be swept off his feet even by Mr. Tubbs’s undertaking to double everybody’s money within a year, through the favor of certain financial parties with whom he was intimate.

“I’ll wait till I see the color of my money before I reckon the interest on it,” he remarked.  “It’s true the cave would be a likely and convenient place for hiding the chest; the question is:  Wouldn’t it be too likely and convenient?  Sampson would maybe not choose the spot of all others where the first comer who had got wind of the story would be certain to look.”

Miss Browne, at this, exchanged darkly significant glances with her two main supporters, and Mr. Tubbs came to the fore with an offer to clinch matters by discovering the grave of Bill Halliwell, with its marked stone, on the point above the cave within twenty-four hours.

“Look for it if you like,” replied Mr. Shaw impatiently.  “But don’t forget that your tombstone is neither more nor less than such a boulder as there are thousands of on the island, and buried under the tropic growth of ninety years besides.”

Miss Browne murmured to Aunt Jane, in a loud aside, that she well understood now why the eminent explorer had not discovered the South Pole, and Aunt Jane murmured back that to her there had always been something so sacred about a tombstone that she couldn’t help wondering if Mr. Shaw’s attitude were really quite reverential.