ng listened; placing his ear to the level of the lake, he very
distinctly heard the noise of a subterranean fall.

"There," said he, rising, "is the discharge of the water; there,
doubtless, by a passage in the granite cliff, it joins the sea, through
cavities which we can use to our profit. Well, I can find it!"

The engineer cut a long branch, stripped it of its leaves, and plunging
it into the angle between the two banks, he found that there was a large
hole one foot only beneath the surface of the water. This hole was the
opening so long looked for in vain, and the force of the current was
such that the branch was torn from the engineer's hands and disappeared.

"There is no doubt about it now," repeated Harding. "There is the
outlet, and I will lay it open to view!"

"How?" asked Gideon Spilett.

"By lowering the level of the water of the lake three feet."

"And how will you lower the level?"

"By opening another outlet larger than this."

"At what place, Cyrus?"

"At the part of the bank nearest the coast."

"But it is a mass of granite!" observed Spilett.

"Well," replied Cyrus Harding, "I will blow up the granite, and the
water escaping, will subside, so as to lay bare this opening--"

"And make a waterfall, by falling on to the beach," added the reporter.

"A fall that we shall make use of!" replied Cyrus. "Come, come!"

The engineer hurried away his companion, whose confidence in Harding was
such that he did not doubt the enterprise would succeed. And yet, how
was this granite wall to be opened without powder, and with imperfect
instruments? Was not this work upon which the engineer was so bent above
their strength?

When Harding and the reporter entered the Chimneys, they found Herbert
and Pencroft unloading their raft of wood.

"The woodmen have just finished, captain." said the sailor, laughing,
"and when you want masons--"

"Masons,--no, but chemists," replied the engineer.

"Yes," added the reporter, "we are going to blow up the island--"

"Blow up the island?" cried Pencroft.

"Part of it, at least," replied Spilett.

"Listen to me, my friends," said the engineer. And he made known to them
the result of his observations.

According to him, a cavity, more or less considerable, must exist in
the mass of granite which supported Prospect Heights, and he intended
to penetrate into it. To do this, the opening through which the water
rushed must first be cleared, and the level lowered