diagonally for the dam, and in a brief time came to the edge of the
shallow channel, which now carried the overflow of the huge reservoir
behind the dam down to the cove.

As he followed this stream, he could not help thinking of the
possibility of a break occurring in the high wall of masonry which
loomed ahead of him. If there should be any undiscovered weakness in the
wall! Or if an enemy should sink a charge of dynamite, or some other
high explosive, at the base of the dam and blow a hole through it!

He did not see any one moving about the dam either above or below. He
knew that on the ridge, level with the top of the barrier, lived a man
they called the dam superintendent. He sometimes walked across the
embankment, from end to end; a privilege forbidden to others.

But Whistler was quite sure that this dam superintendent seldom went to
the foot of the wall, or examined the face of it for any break in the
stonework. Of course, the dam had stood secure for so many years that
it seemed improbable that it would fail in any part now.

But Whistler Morgan was not considering any leakage of the water through
the masonry which might endanger the foundation of the dam. Such seepage
must have shown itself long ago if the barrier had not been properly
constructed.

It was of a sudden, unexpected, and treacherous blow-out that the young
sailor was thinking. That man in the bushes, who had seemed so desirous
of hiding from the passers-by and whose interest in the face of the dam
had been so marked, puzzled Phil and excited his suspicions.