The dog, excited by his master’s words, ran towards the extremity of the cavern, and there redoubled his barking.

They followed him, and by the light of the torches, perceived the mouth of a regular well in the granite. It was by this that the water escaped; and this time it was not an oblique and practicable passage, but a perpendicular well, into which it was impossible to venture.

The torches were held over the opening: nothing could be seen. Harding took a lighted branch, and threw it into the abyss. The blazing resin, whose illuminating power increased still more by the rapidity of its fall, lighted up the interior of the well, but yet nothing appeared. The flame then went out with a slight hiss, which showed that it had reached the water, that is to say, the level of the sea.

The engineer, calculating the time employed in its fall, was able to calculate the depth of the well, which was found to be about ninety feet.

The floor of the cavern must thus be situated ninety feet above the level of the sea.

“Here is our dwelling,” said Cyrus Harding.

“But it was occupied by some creature,” replied Gideon Spilett, whose curiosity was not yet satisfied.

“Well, the creature, amphibious or otherwise, has made off through this opening,” replied the engineer, “and has left the place for us.”

“Never mind,” added the sailor, “I should like very much to be Top just for a quarter of an hour, for he doesn’t bark for nothing!”

Cyrus Harding looked at his dog, and those of his companions who were near him might have heard him murmur these words,—