there was no sign
of it. The course of the cave now changed to the right, and the floor of
the cave went downwardly at a slight descent.

The Professor suddenly restrained the boys. "Wait a moment; the light
behind us should be brought forward to this point."

George went back and brought it up, and after some delay a place for it
was found. The two lights now plainly showed a sudden enlargement in the
area of the cave, and above them hung what appeared to be huge icicles,
giving the interior a weird appearance. Still no water was in sight.

"The white substances we see all around us indicate that above us the
rocks are limestone, and water, in coming through, has acted on the
stone so as to form carbonate of lime, or chalk."

The single lamp was now sufficient to light up the interior, which
looked like a domed iceberg, with all sorts of fantastic figures
standing out in bold relief, which were contrasted by the many dark
recesses irregularly scattered about everywhere.

"I see an opening beyond," was Harry's remark, in a suppressed tone.

The contracted opening was to the left, and he quickly made his way over
the uneven floor to that point. "The water is beyond, and I hear
something there."

George quietly moved forward. The light from the Professor's lamp
glistened on the surface, and rippling waves were easily distinguished.

"What has become of the light we had on the perch?" was the Professor's
startling inquiry.

The boys looked back. It was not there. Probably it had gone out.

"We must not go on until we have relighted it," was the Professor's
caution.

George went back. The light from the Professor's lamp still threw its
rays back to the ledge, which was not more than a hundred feet from
their present location. "I can't find it. It is not here, and I know I
put it on this ledge. Here is the piece of lime I put up against it."

Too startled for words, Harry drew back from the opening. Without
further conversation he and the Professor retraced their steps toward
George, who was now frantically searching every crevice.

"That is too bad. Are you sure this is the place?"

"I am positive of it."

The boys looked at the Professor. He knew they mentally asked whether
they should proceed with the single light. "I think it would be unwise
to go farther with one light only. If we can do no better we can make a
half dozen lights, and light up the whole cave. I am just as much
interested in it now as y