"My friend," replied Harding, "if it is easy for us to reach our dwelling by this passage, it will be equally easy for others besides us. I mean, on the contrary, to block up that opening, to seal it hermetically, and, if it is necessary, to completely hide the entrance by making a dam, and thus causing the water of the lake to rise."

"And how shall we get in?" asked the sailor.

"By an outside ladder," replied Cyrus Harding, "a rope ladder, which, once drawn up, will render access to our dwelling impossible."

"But why so many precautions?" asked Pencroft. "As yet we have seen no dangerous animals. As to our island being inhabited by natives, I don't believe it!"

"Are you quite sure of that, Pencroft?" asked the engineer, looking at the sailor.

"Of course we shall not be quite sure, till we have explored it in every direction," replied Pencroft.

"Yes," said Harding, "for we know only a small portion of it as yet. But at any rate, if we have no enemies in the interior, they may come from the exterior, for parts of the Pacific are very dangerous. We must be provided against every contingency."