"Explain yourself, Cyrus!" said Gideon Spilett.
"I will do so," replied Cyrus Harding, "or rather I will give you the explanation which, during our few minutes of private conversation, was given me by Captain Nemo."
"Captain Nemo!" exclaimed the colonists.
"Yes, and it was the last service he desired to render us before his death."
"The last service!" exclaimed Pencroft. "You will see that though he is dead he will render us others yet!"
"But what did the captain say?" inquired the reporter.
'I will tell you my friends," said the engineer. "Lincoln Island does not resemble the other islands of the Pacific, and a fact of which Captain Nemo told me must sooner or later bring about its destruction."
"Nonsense! Lincoln Island, it can't be!" cried Pencroft, who in spite of the respect he felt for Cyrus Harding, could not prevent a gesture of incredulity.
"Listen, Pencroft," resumed the engineer, "I will tell you what Captain Nemo communicated to me, and which I myself confirmed yesterday, during the exploration of Dakkar Grotto. This cavern stretches under the island as far as the volcano, and is only separated from its central shaft by the wall which terminates it. Now, this wall is seamed with fissures and clefts which already allow the sulphurous gases generated in the interior of the volcano to escape."
"Well?" said Pencroft, his brow suddenly contracting.
"Well, then, I saw that these fissures are widening under the internal pressure from within, that the wall of basalt is gradually giving way, and that sooner or later it will afford a passage to the waters of the cavern."
"Good!" replied Pencroft, with an attempt at pleasantry. "The sea will extinguish the volcano, and there will be an end to the matter!"
"Not so!" said Cyrus Harding, "should a day arrive when the sea, rushing through the wall of the cavern, penetrates by the central shaft into the interior of the island to the boiling lava, Lincoln Island will that day be blown into the air—just as would happen to the island of Sicily were the Mediterranean to precipitate itself into Mount Etna."
There was no answer to these startling words. The colonists now understood the danger which menaced them.
