acid,
saltpeter, sulphur, and coal. Unhappily, it is the guns which we have
not got.

"Oh, captain," replied the sailor, "with a little determination--"

Pencroft had erased the word "impossible" from the dictionary of Lincoln
Island.

The settlers, having arrived at Prospect Heights, went immediately
towards that point of the lake near which was the old opening now
uncovered. This outlet had now become practicable, since the water no
longer rushed through it, and it would doubtless be easy to explore the
interior.

In a few minutes the settlers had reached the lower point of the lake,
and a glance showed them that the object had been attained.

In fact, in the side of the lake, and now above the surface of the
water, appeared the long-looked-for opening. A narrow ridge, left bare
by the retreat of the water, allowed them to approach it. This orifice
was nearly twenty feet in width, but scarcely two in height. It was like
the mouth of a drain at the edge of the pavement, and therefore did
not offer an easy passage to the settlers; but Neb and Pencroft, taking
their pickaxes, soon made it of a suitable height.

The engineer then approached, and found that the sides of the opening,
in its upper part at least, had not a slope of more than from thirty to
thirty-five degrees. It was therefore practicable, and, provided that
the declivity did not increase, it would be easy to descend even to the
level of the sea. If then, as was probable, some vast cavity existed in
the interior of the granite, it might, perhaps, be of great use.

"Well, captain, what are we stopping for?" asked the sailor, impatient
to enter the narrow passage. "You see Top has got before us!"

"Very well," replied the engineer. "But we must see our way. Neb, go and
cut some resinous branches."

Neb and Herbert ran to the edge of the lake, shaded with pines and other
green trees, and soon returned with some branches, which they made
into torches. The torches were lighted with flint and steel, and Cyrus
Harding leading, the settlers ventured into the dark passage, which the
overplus of the lake had formerly filled.

Contrary to what might have been supposed, the diameter of the passage
increased as the explorers proceeded, so that they very soon were able
to stand upright. The granite, worn by the water for an infinite time,
was very slippery, and falls were to be dreaded. But the settlers were
all attached to each other by a cord, as is frequentl