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.

They continued their labors during the whole of this day, the 3rd of January, without thinking further of the volcano, which could not, besides, be seen from the shore of Granite House.  But once or twice, large shadows, veiling the sun, which described its diurnal arc through an extremely clear sky, indicated that a thick cloud of smoke passed between its disc and the island.  The wind, blowing on the shore, carried all these vapors to the westward.  Cyrus Harding and Gideon Spilett remarked these somber appearances, and from time to time discussed the evident progress of the volcanic phenomena, but their work went on without interruption.  It was, besides, of the first importance from every point of view, that the vessel should be finished with the least possible delay.  In presence of the eventualities which might arise, the safety of the colonists would be to a great extent secured by their ship.  Who could tell that it might not prove some day their only refuge?

In the evening, after supper, Cyrus Harding, Gideon Spilett, and Herbert again ascended the plateau of Prospect Heights.  It was already dark, and the obscurity would permit them to ascertain if flames or incandescent matter thrown up by the volcano were mingled with the vapor and smoke accumulated at the mouth of the crater.

“The crater is on fire!” said Herbert, who, more active than his companion, first reached the plateau.

Mount Franklin, distant about six miles, now appeared like a gigantic torch, around the summit of which turned fuliginous flames.  So much smoke, and possibly scoriae and cinders were mingled with them, that their light gleamed but faintly amid the gloom of the night.  But a kind of lurid brilliancy spread over the island, against which stood out confusedly the wooded masses of the heights.  Immense whirlwinds of vapor obscured the sky, through which glimmered a few stars.

“The change is rapid!” said the engineer.

“That is not surprising,” answered the reporter.  “The reawakening of the volcano already dates back some time.  You may remember, Cyrus, that the first vapors appeared about the time we searched the sides of the mountain to discover Captain Nemo’s retreat.  It was, if I mistake not, about the 15th of October.”

“Yes,” replied Herbert, “two months and a half ago!”

“The subterranean fires have therefore been smoldering for ten weeks,” resumed Gideon Spilett, “and it is not to be wondered at that they now break out with such violence!”

“Do not you feel a certain vibration of the soil?” asked Cyrus Harding.

“Yes,” replied Gideon Spilett, “but there is a great difference between that and an earthquake.”