f a bridge, under which rushed the foaming water.

Leaning forward, the engineer saw a black object floating on the water.
He drew it towards him. It was a boat, moored to some interior
projection of the cave. This boat was iron-plated. Two oars lay at the
bottom.

"Jump in!" said Harding.

In a moment the settlers were in the boat. Neb and Ayrton took the
oars, Pencroft the rudder. Cyrus Harding in the bows, with the lantern,
lighted the way.

The elliptical roof, under which the boat at first passed, suddenly
rose; but the darkness was too deep, and the light of the lantern too
slight, for either the extent, length, height, or depth of the cave to
be ascertained. Solemn silence reigned in this basaltic cavern. Not a
sound could penetrate into it, even the thunder peals could not pierce
its thick sides.

Such immense caves exist in various parts of the world, natural crypts
dating from the geological epoch of the globe. Some are filled by the
sea; others contain entire lakes in their sides. Such is Fingal's Cave,
in the island of Staffa, one of the Hebrides; such are the caves of
Morgat, in the bay of Douarucuez, in Brittany, the caves of Bonifacier,
in Corsica, those of Lyse-Fjord, in Norway; such are the immense Mammoth
caverns in Kentucky, 500 feet in height, and more than twenty miles in
length! In many parts of the globe, nature has excavated these caverns,
and preserved them for the admiration of man.

Did the cavern which the settlers were now exploring extend to the
centre of the island? For a quarter of an hour the boat had been
advancing, making _detours_, indicated to Pencroft by the engineer in
short sentences, when all at once--

"More to the right!" he commanded. The boat, altering its course, came
up alongside the right wall. The engineer wished to see if the wire
still ran along the side. The wire was there fastened to the rock.
"Forward!" said Harding.

And the two oars, plunging into the dark waters, urged the boat onwards.

On they went for another quarter of an hour, and a distance of
half-a-mile must have been cleared from the mouth of the cave, when
Harding's voice was again heard. "Stop!" said he.

The boat stopped, and the colonists perceived a bright light
illuminating the vast cavern, so deeply excavated in the bowels of the
island, of which nothing had ever led them to suspect the existence.

At a height of a hundred feet rose the vaulted roof, supported on basalt