The colonists worked with a will, and the two dams which besides did not exceed eight feet in width by three in height, were rapidly erected by means of well-cemented blocks of stone.

This work finished, it would have been impossible to guess that at that part of the lake, there existed a subterranean passage through which the overflow of the lake formerly escaped.

Of course the little stream which fed the reservoir of Granite House and worked the lift, had been carefully preserved, and the water could not fail. The lift once raised, this sure and comfortable retreat would be safe from any surprise.

This work had been so quickly done, that Pencroft, Gideon Spilett, and Herbert found time to make an expedition to Port Balloon, The sailor was very anxious to know if the little creek in which the "Bonadventure" was moored, had been visited by the convicts.

"These gentlemen," he observed, "landed on the south coast, and if they followed the shore, it is to be feared that they may have discovered the little harbor, and in that case, I wouldn't give half-a-dollar for our 'Bonadventure.'"

Pencroft's apprehensions were not without foundation, and a visit to Port Balloon appeared to be very desirable. The sailor and his companions set off on the 10th of November, after dinner, well armed. Pencroft, ostentatiously slipping two bullets into each barrel of his rifle, shook his head in a way which betokened nothing good to any one who approached too near him, whether "man or beast," as he said. Gideon Spilett and Herbert also took their guns, and about three o'clock all three left Granite House.

Neb accompanied them to the turn of the Mercy, and after they had crossed, he raised the bridge. It was agreed that a gunshot should announce the colonists' return, and that at the signal Neb should return and reestablish the communication between the two banks of the river.

The little band advanced directly along the road which led to the southern coast of the island. This was only a distance of three miles and a half, but Gideon Spilett and his companions took two hours to traverse it. They examined all the border of the road, the thick forest, as well as Tabor Marsh. They found no trace of the fugitives who, no doubt, not having yet discovered the number of the colonists, or the means of defense which they had at their disposal, had gained the less accessible parts of the island.

Arrived at Port Balloon, Pencroft saw with extreme satisfaction that the "Bonadventure" was tranquilly floating in the narrow creek. However, Port Balloon was so well hidden among high rocks, that it could scarcely be discovered either from the land or the sea.

"Come," said Pencroft, "the blackguards have not been there yet. Long grass suits reptiles best, and evidently we shall find them in the Far West."

"And it's very lucky, for if they had found the 'Bonadventure'," added Herbert, "they would have gone off in her, and we should have been prevented from returning to Tabor Island."

"Indeed," remarked the reporter, "it will be important to take a document there which will make known the situation of Lincoln Island, and Ayrton's new residence, in case the Scotch yacht returns to fetch him."

"Well, the 'Bonadventure' is always there, Mr. Spilett," answered the sailor. "She and her crew are ready to start at a moment's notice!"

"I think, Pencroft, that that is a thing to be done after our exploration of the island is finished. It is possible after all that the stranger, if we manage to find him, may know as much about Tabor Island as about Lincoln Island. Do not forget that he is certainly the author of the document, and he may, perhaps, know how far we may count on the return of the yacht!"

"But!" exclaimed Pencroft, "who in the world can he be? The fellow knows us and we know nothing about him! If he is a simple castaway, why should he conceal himself! We are honest men, I suppose, and the society of honest men isn't unpleasant to any one. Did he come here voluntarily? Can he leave the island if he likes? Is he here still? Will he remain any longer?"

Chatting thus, Pencroft, Gideon Spilett, and Herbert got on board and looked about the deck of the "Bonadventure." All at once, the sailor having examined the bitts to which the cable of the anchor was secured,--

"Hallo," he cried, "this is queer!"

"What is the matter, Pencroft?" asked the reporter.