There the river was eighty feet in breadth, which was awkward to cross, but as Pencroft had taken upon himself to conquer this difficulty, he was compelled to do it.  The settlers certainly had reason to be pretty tired.  The journey had been long, and the task of getting down the balloon had not rested either their arms or legs.  They were anxious to reach Granite House to eat and sleep, and if the bridge had been constructed, in a quarter of an hour they would have been at home.

The night was very dark.  Pencroft prepared to keep his promise by constructing a sort of raft, on which to make the passage of the Mercy.  He and Neb, armed with axes, chose two trees near the water, and began to attack them at the base.

Cyrus Harding and Spilett, seated on the bank, waited till their companions were ready for their help, while Herbert roamed about, though without going to any distance.  All at once, the lad, who had strolled by the river, came running back, and, pointing up the Mercy, exclaimed,—­

“What is floating there?”

Pencroft stopped working, and seeing an indistinct object moving through the gloom,—­

“A canoe!” cried he.

All approached, and saw to their extreme surprise, a boat floating down the current.

“Boat ahoy!” shouted the sailor, without thinking that perhaps it would be best to keep silence.

No reply.  The boat still drifted onward, and it was not more than twelve feet off, when the sailor exclaimed,—­

“But it is our own boat! she has broken her moorings, and floated down the current.  I must say she has arrived very opportunely.”

“Our boat?” murmured the engineer.

Pencroft was right.  It was indeed the canoe, of which the rope had undoubtedly broken, and which had come alone from the sources of the Mercy.  It was very important to seize it before the rapid current should have swept it away out of the mouth of the river, but Neb and Pencroft cleverly managed this by means of a long pole.

The canoe touched the shore.  The engineer leaped in first, and found, on examining the rope, that it had been really worn through by rubbing against the rocks.

“Well,” said the reporter to him, in a low voice, “this is a strange thing.”

“Strange indeed!” returned Cyrus Harding.

Strange or not, it was very fortunate.  Herbert, the reporter, Neb, and Pencroft, embarked in turn.  There was no doubt about the rope having been worn through, but the astonishing part of the affair was, that the boat should arrive just at the moment when the settlers were there to seize it on its way, for a quarter of an hour earlier or later it would have been lost in the sea.

If they had been living in the time of genii, this incident would have given them the right to think that the island was haunted by some supernatural being, who used his power in the service of the castaways!