stone, which
was round in shape, was pulled back against the entrance, and all was
darkness, save for one crevice an inch or two wide.

The Greek peered sharply through this, and then exclaimed in a low
whisper: "We are just in time. A party of Abyssinians are approaching
through the jungle in pursuit of the Galla fugitive.

"Hush!" he added; "don't make a sound; they are coming directly toward
the rock."

CHAPTER XVIII.

THE UNDERGROUND RIVER.

A moment of terrible suspense followed the Greek's announcement. From
without could be plainly heard a chorus of angry shouts as the
Abyssinians searched for their missing prey.

Then the sounds grew fainter and Canaris said quietly: "They have gone
on past the rock. We had better strike a light and see what has become
of that black rascal. I cannot understand how he knew anything about
this place. It may not be the proper entrance after all."

One of the bronze lamps was filled with palm oil and lighted, and Guy
undertook to lead the way into the depths of the cavern.

The passage was amply large enough to hold two or three men standing up,
but it led downward at a very sharp angle. The journey was performed in
silence, and after traveling ten or fifteen minutes Guy stopped.

A vast empty space was before him, and at his feet lay a sharp slope of
loose earth. Here were seen the tracks of the savage, and without
hesitation Guy began the descent, and half crawling, half sliding,
reached firm ground a few yards below.

Melton and Canaris were close behind, and together they went up into
the vast expanse of the cavern. Under foot was hard, compact sand, and
in a moment more the glare of the lamp was reflected on running water,
and they stood on the brink of the mysterious underground river.

"We have found it?" exclaimed Canaris exultingly. "The Englishman was
right."

It was impossible to judge of the width of the stream. It might be very
narrow and it might be very broad. The flowing water made not a sound,
and yet the current was swift, for a bit of paper that Melton tossed in
was snatched from sight immediately.

As they gazed on this strange sight with emotions that it would be
impossible to describe, a vague, shadowy object passed down the stream
and vanished in the darkness.

"There goes that fellow," cried Guy. "He has escaped in a canoe," and
hastening up along the shore, waving the lamp in fron