“Yes,” said the reporter, “we ought to make known to that vessel, whoever she may be, that the island is inhabited.  To neglect the opportunity which is offered to us might be to create everlasting regrets.”

It was therefore decided that Neb and Pencroft should go to Port Balloon, and that there, at nightfall, they should light an immense fire, the blaze of which would necessarily attract the attention of the brig.

But at the moment when Neb and the sailor were preparing to leave Granite House, the vessel suddenly altered her course, and stood directly for Union Bay.  The brig was a good sailer, for she approached rapidly.  Neb and Pencroft put off their departure, therefore, and the glass was put into Ayrton’s hands, that he might ascertain for certain whether the ship was or was not the “Duncan.”  The Scotch yacht was also rigged as a brig.  The question was, whether a chimney could be discerned between the two masts of the vessel, which was now at a distance of only five miles.

The horizon was still very clear.  The examination was easy, and Ayrton soon let the glass fall again, saying—­

“It is not the ‘Duncan’!  It could not be!”

Pencroft again brought the brig within the range of the telescope, and could see that she was of between three and four hundred tons burden, wonderfully narrow, well-masted, admirably built, and must be a very rapid sailer.  But to what nation did she belong?  That was difficult to say.

“And yet,” added the sailor, “a flag is floating from her peak, but I cannot distinguish the colors of it.”

“In half an hour we shall be certain about that,” answered the reporter.  “Besides, it is very evident that the intention of the captain of this ship is to land, and, consequently, if not today, to-morrow at the latest, we shall make his acquaintance.”

“Never mind!” said Pencroft.  “It is best to know whom we have to deal with, and I shall not be sorry to recognize that fellow’s colors!”

And, while thus speaking, the sailor never left the glass.  The day began to fade, and with the day the breeze fell also.  The brig’s ensign hung in folds, and it became more and more difficult to observe it.

“It is not the American flag,” said Pencroft from time to time, “nor the English, the red of which could be easily seen, nor the French or German colors, nor the white flag of Russia, nor the yellow of Spain.  One would say it was all one color.  Let’s see:  in these seas, what do we generally meet with?  The Chilean flag?—­but that is tri-color.  Brazilian?—­it is green.  Japanese?—­it is yellow and black, while this—­”

At that moment the breeze blew out the unknown flag.  Ayrton seizing the telescope which the sailor had put down, put it to his eye, and in a hoarse voice,—­

“The black flag!” he exclaimed.

And indeed the somber bunting was floating from the mast of the brig, and they had now good reason for considering her to be a suspicious vessel!