more air. I'm afraid something has gone wrong down there--I mean
something new. Maybe his suit is punctured and he's being drowned."

"Oh, if we could only do something!" exclaimed Mr. Blair. He stood with
Joe, just outside the gate house. On the broad top of the dam, a few
feet above the surface of the water, the pumping apparatus was set up.
Near it were the tools used by the diver in the repair work.

Going down into the water was the air hose, through which oxygen was
supplied. A few bubbles rising to the surface told that the hose was
still connected with the diver's helmet. In addition to the hose a
light but strong line led into the water. A man held this in his hand,
and it was by a series of jerks on this that the diver below
communicated with his helpers above. Then there was a heavy rope made
fast to a ring in the wall. The other end was attached to the diver's
belt.

And these three things--a rope, a line and a hose descending into the
mysterious water--were the only links that connected the diver with
life. That he was still alive was evident, for now and then there came
a feeble pull on the life-line.

Two men had hold of the heavy rope, the end of which was in the diver's
belt, and, from time to time, they pulled on it, hoping that the
unfortunate man had been able to free himself, so he could be pulled
up.

But the rope remained taut--it did not give. The diver was still caught
in the outlet pipe--just how no one could say.

"Can't they drain the reservoir?" asked Joe. "Surely, to save a life,
the towns could do without water for a while."

"Oh, we'd drain it in a minute if we could," said Mr. Blair. "But you
see now we can't get the main outlet pipe open. It's in that one that
the diver is stuck. Only a little water is now flowing through it. We
have opened all the small outlets we can, but it will take three or
four days to empty the reservoir through them."

"Three or four days," murmured Joe. "And in the meanwhile----"

He did not care to finish the sentence.

Again came a quick signal on the life-line.

"He wants more air!" cried the man who interpreted the jerks. "Give him
more air, boys!"

The men at the wheel of the air pump worked it faster. Though why an
increased pressure was wanted no one knew.

"Helen," said Joe in a low voice, "I'm going to try to save that man. I
can't bear to stand here and think he may be slowly dying down there,"
and he pointed to the calm water, unruf