Mr. Chalk, deep in thought, paced up and down in silence.

“That’s a secret,” said Brisket.  “I don’t want them to think that I was spying.  I told you because you understand.  A shipmaster has to keep his eyes open, for everybody’s sake.”

“It’s your duty,” said Mr. Chalk, firmly.

Captain Brisket, with a little display of emotion, thanked him, and, leaning against the side, drew his attention to the beauty of the stars and sea.  Impelled by the occasion and the charm of the night he waxed sentimental, and with a strange mixture of bluffness and shyness spoke of his aged mother, of the loneliness of a seafarer’s life, and the inestimable boon of real friendship.  He bared his inmost soul to his sympathetic listener, and then, affecting to think from a remark of Mr. Chalk’s that he was going to relate the secret of the voyage, declined to hear it on the ground that he was only a rough sailorman and not to be trusted.  Mr. Chalk, contesting this hotly, convinced him at last that he was in error, and then found that, bewildered by the argument, the captain had consented to be informed of a secret which he had not intended to impart.

“But, mind,” said Brisket, holding up a warning finger, “I’m not going to tell Peter Duckett.  There’s no need for him to know.”

Mr. Chalk said “Certainly not,” and, seeing no way for escape, led the reluctant man as far from the helmsman as possible and whispered the information.  By the time they parted for the night Captain Brisket knew as much as the members of the expedition themselves, and, with a rare thoughtfulness, quieted Mr. Chalk’s conscience by telling him that he had practically guessed the whole affair from the beginning.

[Illustration:  “He led the reluctant man as far from the helmsman as possible and whispered the information.”]

He listened with great interest a few days later when Mr. Tredgold, after considering audibly which island he should visit first, gave him the position of Bowers’s Island and began to discuss coral reefs and volcanic action.  They were now well in among the islands.  Two they passed at a distance, and went so close to a third—­a mere reef with a few palms upon it—­that Mr. Chalk, after a lengthy inspection through his binoculars, was able to declare it uninhabited.

A fourth came into sight a couple of days later:  a small grey bank on the starboard bow.  Captain Brisket, who had been regarding it for some time with great care, closed his glass with a bang and stepped up to Mr. Tredgold.

“There she is, sir,” he said, in satisfied tones.

Mr. Tredgold, who was drinking tea, put down his cup, and rose with an appearance of mild interest.  Mr. Stobell followed suit, and both gazed in strong indignation at the undisguised excitement of Mr. Chalk as he raced up the rigging for a better view.  Tredgold with the captain’s glass, and Stobell with an old pair of field-glasses in which he had great faith, gazed from the deck.  Tredgold was the first to speak.