mitating Harry in the building operation. The sudden appearance did not
startle him in the least, nor did he stop beating his lullaby, after he
noticed the broad smiles that greeted him.

With an eye to every advantage, Harry had attached to the sides of the
boat, amidships, two short standards, about three feet high, on top of
which two of the lamps were mounted, so they would be out of the way,
and thus give them freedom to handle the oars and the weapons, as well
as afford them a better light, than if carried by hand. The Professor
was much pleased with this arrangement.

The boat was not particularly heavy, but it was a task to drag it over
the uneven floor and along the tortuous path which had to be taken by
their burden, but when the water was reached they were repaid for the
labor by the ease with which they could explore the interior.

Before starting the journey the Professor, as usual, uttered a few words
of advice: "One of us must sit in the bow, one at the stern, and the
other amidships. The one at the stern must propel the boat, as we cannot
row through many of the places, and as the water is not deep, that will
not be a difficult task. The ones at the bow and amidships should have
the guns, and if there is no objection, I will take my place on the
middle seat, where I can best take the observations on the way. The
other places you should decide between yourselves."

"I am willing to take the bow, if Harry agrees." Harry sanctioned the
arrangement, and when the lamps were securely fastened, Harry pushed the
boat forward through the cavern. It did not take long to reach the
slight turn which led to the large chamber, which was over one hundred
feet long.

On the way to the chamber Harry had an opportunity to measure the depths
of the water, and at intervals the Professor would call out for the
depths, as he was making notes of the descent formed by the floor to the
chamber. The oars gave a pretty fair idea, showing that the floor was
only about five feet lower at the chamber than where the boat was
launched.

Reaching the chamber Harry was directed to steer it to the right and
skirt the wall going to the left, so that every part of it could be
examined.

[Illustration: _Fig. 13 THE TREASURE CAVE_]

"I have another reason for this careful examination," remarked the
Professor, as he was intently engaged in making notes on the board
tablets. "It may be likely that the chamber has more than one outlet a