“It is used in alloys and medicines,” he explained.  “To us it is useless.”

He threw the piece of rock contemptuously among the bushes.  But, being thorough in all that he undertook, he returned to the cave and again conducted an inquisition.  The silver-hued vein became more strongly marked at the point where it disappeared downwards into a collection of rubble and sand.  That was all.  Did men give their toil, their lives, for this?  So it would appear.  Be that as it might, he had a more pressing work.  If the cave still held a secret it must remain there.

Iris had gone back to her sago-kneading.  Necessity had made the lady a bread-maid.

“Fifteen hundred years of philology bridged by circumstance,” mused Jenks.  “How Max Mueller would have reveled in the incident!”

Shouldering the axe he walked to the beach.  The tide was low and the circular sweep of the reef showed up irregularly, its black outlines sticking out of the vividly green water like jagged teeth.

Much debris from the steamer was lying high and dry.  It was an easy task for an athletic man to reach the palm tree, yet the sailor hesitated, with almost imperceptible qualms.

“A baited rat-trap,” he muttered.  Then he quickened his pace.  With the first active spring from rock to rock his unacknowledged doubts vanished.  He might find stores of priceless utility.  The reflection inspired him.  Jumping and climbing like a cat, in two minutes he was near the tree.

He could now see the true explanation of its growth in a seemingly impossible place.  Here the bed of the sea bulged upwards in a small sand cay, which silted round the base of a limestone rock, so different in color and formation from the coral reef.  Nature, whose engineering contrivances can force springs to mountain tops, managed to deliver to this isolated refuge a sufficient supply of water to nourish the palm, and the roots, firmly lodged in deep crevices, were well protected from the waves.

Between the sailor and the tree intervened a small stretch of shallow water.  Landward this submerged saddle shelved steeply into the lagoon.  Although the water in the cove was twenty fathoms in depth, its crystal clearness was remarkable.  The bottom, composed of marvelously white sand and broken coral, rendered other objects conspicuous.  He could see plenty of fish, but not a single shark, whilst on the inner slope of the reef was plainly visible the destroyed fore part of the Sirdar, which had struck beyond the tree, relatively to his present standpoint.  He had wondered why no boats were cast ashore.  Now he saw the reason.  Three of them were still fastened to the davits and carried down with the hull.

Seaward the water was not so clear.  The waves created patches of foam, and long submarine plants swayed gently in the undercurrent.

To reach Palm-tree Rock—­anticipating its subsequent name—­he must cross a space of some thirty feet and wade up to his waist.