Although the edifice required at least two more days of hard work before it would be fit for habitation Iris wished to take up her quarters there immediately.  This the sailor would not hear of.

“In the cave,” he said, “you are absolutely sheltered from all the winds that blow or rain that falls.  Our villa, however, is painfully leaky and draughty at present.  When asleep, the whole body is relaxed, and you are then most open to the attacks of cold or fever, in which case, Miss Deane, I shall be reluctantly obliged to dose you with a concoction of that tree there.”

He pointed to a neighboring cinchona, and Iris naturally asked why he selected that particular brand.

“Because it is quinine, not made up in nice little tabloids, but au naturel.  It will not be a bad plan if we prepare a strong infusion, and take a small quantity every morning on the excellent principle that prevention is better than cure.”

The girl laughed.

“Good gracious!” she said; “that reminds me—­”

But the words died away on her lips in sudden fright.  They were standing on the level plateau in front of the cave, well removed from the trees, and they could see distinctly on all sides, for the sun was sinking in a cloudless sky and the air was preternaturally clear, being free now from the tremulous haze of the hot hours.

Across the smooth expanse of sandy ground came the agonized shrieks of a startled bird—­a large bird, it would seem—­winging its way towards them with incredible swiftness, and uttering a succession of loud full-voiced notes of alarm.

Yet the strange thing was that not a bird was to be seen.  At that hour the ordinary feathered inhabitants of the island were quietly nestling among the branches preparatory to making a final selection of the night’s resting-place.  None of them would stir unless actually disturbed.

Iris drew near to the sailor.  Involuntarily she caught his arm.  He stepped a half-pace in front of her to ward off any danger that might be heralded by this new and uncanny phenomenon.  Together they strained their eyes in the direction of the approaching sound, but apparently their sight was bewitched; as nothing whatever was visible.

“Oh, what is it?” wailed Iris, who now clung to Jenks in a state of great apprehension.

The clucking noise came nearer, passed them within a yard, and was already some distance away towards the reef when the sailor burst into a hearty laugh, none the less genuine because of the relief it gave to his bewildered senses.

Reassured, but still white with fear, Iris cried:  “Do speak, please, Mr. Jenks.  What was it?”

“A beetle!” he managed to gasp.

“A beetle?”

“Yes, a small, insignificant-looking fellow, too—­so small that I did not see him until he was almost out of range.  He has the loudest voice for his size in the whole of creation.  A man able to shout on the same scale could easily make himself heard for twenty miles.”