epth of about three yards and a half did not give them a very great
submersion.

To be supplied with condensed air, to be armed, and well lighted up by
the sun was delightful. They walked along the bottom of the sea, easily
seeing the smallest object on all sides of them.

After some little walking they came to several oyster banks, from which
the shells containing the valuable pearls were dragged by the hands of
the divers.

There were millions of them, and the mine seemed inexhaustible.

They could not stop to examine everything, for it was necessary to
follow the captain everywhere.

The road was uneven; sometimes Mont could raise his arm and put his hand
out of the water; at others, he was descending a slope, and the sun's
rays were not so vivid.

Everything became more obscure, and great shells were seen sticking to
curiously shaped rocks.

After a time a large grotto appeared before them, dimly lighted.

The captain entered, followed by the rest of the party, the professor
eagerly taking note of everything.

Stump carried his harpoon, which was a good deal longer than himself;
and the two boys eagerly looked for pearls, as if they expected to find
them lying at their feet.

Descending an inclined plane, Captain Vindex stopped and pointed out an
object which they had not hitherto perceived.

It was an oyster of gigantic size.

Lying alone upon the granite rock, it took up a large space, and never
had the professor even heard of such a huge bivalve.

The shells were open a little, as if the oyster was feeding, which
enabled the captain to introduce his knife.

Keeping the two shells open by both ends of his knife, he pushed back
the flesh of the oyster and revealed a pearl as big as a small cocoanut.

It was a pearl worth at least a hundred thousand dollars.

CHAPTER XXV.

THE MAN OF MYSTERY.

Mont advanced to the oyster, and stretched out his hand as if he would
have seized the pearl, but he was disappointed.

By a sudden movement the captain withdrew his knife, and the two shells
came together with a sharp snap.

Satisfied with showing them this treasure of the deep, he turned round,
and retraced his steps, leaving the precious pearl behind them.

Incomprehensible man, he was now more than ever a mystery to our hero.

He allowed them to seek and take numerous other pearls, but would not
let them touch that he had shown them.

Again they wandered along the bottom of the sea, beh