and farther on it must reach the roof."

Gwyn needed no telling, for the reflection of their lights was glancing
from the floor, and he knew perfectly well that no water ought to be
there.

A chill ran through him--a sensation such as he would have experienced
had he suddenly plunged neck deep in the icy water, and he turned a look
full of agony at Joe, who caught at his arm.

"The sea has broken in--the sea has broken in!" he cried; and quick as
lightning Gwyn bent down, scooped up some of the black-looking water,
and held it to his lips.

It was unmistakably brackish.

"It can't have broke in, my lads--it can't," cried Hardock. "Come on,
and let's go round by the pillar place and get to the men as quick as we
can. There must be some spring burst out; but they'll set the pumps at
work as soon as they know, and soon pull it down again. Come on."

With their hearts beating heavily from excitement, the two lads followed
the captain as he hurried back along the gallery to the spot where they
had turned down; and then, as fast as they could go, they made for the
pillared hall, expecting to find some of the men close by; but when they
reached it, there being no sign of water, there was not a soul visible.
There was proof, though, that it was not long since there were men
there, for the ends of two candles were still burning where they had
been stuck against the wall; tools were lying here and there, and a
couple of half-filled skeps were standing on the low four-wheeled trucks
waiting to be run along the little tramway to the shaft.

No one said so, but each saw for certain that there must have been a
sudden alarm, and the men had fled.

"Come on," said Hardock, hoarsely; but his heart was sinking, and Gwyn
knew that there was a gradual descent toward the bottom of the shaft.
But they walked rapidly on for fully half-an-hour before they came to
the first trace of water, and it was startling when they did.

The gallery they were in entered the next--a lower one--at right-angles;
and as they reached that end dry-footed, their lights gleamed from the
face of running water which was gliding rapidly by in a regular stream
of a few inches deep.

It was Joe who stooped quickly down now to scoop up some of the water
and taste it, which he did in silence.

"Salt?" cried Gwyn, sharply.

There was no reply, and the lad followed his companion's example and
tasted the water.

"Salt, sir?" said Hardock.

"As the sea,"