"Who knows?" answered the sailor. "Perhaps there may be some valuable substance in this volcano, which it will spout forth, and which we may turn to good account!" Cyrus Harding shook his head with the air of a man who augured no good from the phenomenon whose developments had been so sudden. He did not regard so lightly as Pencroft the results of an eruption. If the lava, in consequence of the position of the crater, did not directly menace the wooded and cultivated parts of the island, other complications might present themselves. In fact, eruptions are not unfrequently accompanied by earthquakes; and an island of the nature of Lincoln Island formed of substances so varied, basalt on one side, granite on the other, lava on the north, rich soil on the south, substances which consequently could not be firmly attached to each other, would be exposed to the risk of disintegration. Although, therefore, the spreading of the volcanic matter might not constitute a serious danger, any movement of the terrestrial structure which should shake the island might entail the gravest consequences. "It seems to me," said Ayrton, who had reclined so as to place his ear to the ground, "it seems to me that I can hear a dull, rumbling sound, like that of a wagon loaded with bars of iron." The colonists listened with the greatest attention, and were convinced that Ayrton was not mistaken. The rumbling was mingled with a subterranean roar, which formed a sort of _rinforzando_, and died slowly away, as if some violent storm had passed through the profundities of the globe. But no explosion, properly so termed, could be heard. It might therefore be concluded that the vapours and smoke found a free passage through the central shaft; and that the safety-valve being sufficiently large, no convulsion would be produced, no explosion was to be apprehended. "Well, then!" said Pencroft, "are we not going back to work? Let Mount Franklin smoke, groan, bellow, or spout forth fire and flame as much as it pleases, that is no reason why we should be idle! Come, Ayrton, Neb, Herbert, Captain Harding, Mr Spilett, every one of us must turn to at our work to-day! We are going to place the keelson, and a dozen pair of hands would not be too many. Before two months I want our new _Bonadventure_--for we shall keep the old name, shall we not?--to float on the waters of Port Balloon! Therefore there is not an hour to lose!" All the colonists, their services thus requisitioned by Pencroft, descended to the dockyard, and proceeded to place the keelson, a thick mass of wood which forms the lower portion of a ship and unites firmly the timbers of the hull. It was an arduous undertaking, in which all took part.