e, 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.

They continued their labours 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 va