t as we were the last time."

"But how can we possibly chart the cave when we have only one boat?" And
George laughed at the idea of making a plan of the interior by standing
at one point.

"You measured the height of the falls without going to the top, if you
will remember."

He had forgotten that. But the boat was at last secured in the wagon,
and proceeded to the cliffs. It was fortunate that the team could be
taken to a point directly over the mouth of the cave, and in a little
while the ropes were attached to it and slowly lowered, Harry taking the
precaution to follow it down and to dislodge it from the steps which
appeared in its path.

The team was then securely hitched, and taking all their implements,
such as lamps and boards, together with two of the guns and an ample
supply of ammunition, descended to the entrance. The boat was at the
mouth, and it was suggested that a preliminary survey of the interior
should first be made, in order to ascertain how far the boat would have
to be carried before reaching the water.

The lamps were lighted, and the boys led the way. After passing the
point, about two hundred feet from the mouth, and at almost the
identical spot where the water was found at the first exploration, the
water glistened before them. Returning toward the opening a loud beating
sound was heard, which at first startled them. It was evidently at the
mouth of the cave. It sounded like the beating of a stick against some
hard substance.

The nearer they came to daylight, the more distinct were the sounds. As
heretofore explained, near the entrance the cave made a turn to the
right at an angle, so that when at a distance of fifty feet from the
opening it was impossible to see daylight, except what little was
diffracted from the angle at the turn.

This angle was reached, and the beating, rather irregular, was plain
enough to cause some alarm. The boat was beyond the open mouth and at
one side, so that it could not be seen by anyone within the recessed
walls.

All stood still, while the beatings continued. Occasionally there would
be a cessation, to be repeated again. Whatever it was it was not far
away. The Professor whispered: "Get the guns ready; we must take some
chances."

Cautiously the company moved forward; the end of the boat first appeared
in sight, and as George peered beyond the projecting point of the ledge,
he threw up his hands and burst out in laughter. Angel was in the boat,
i