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.

Blake. And Blake was an English name! He looked about as much like an
Englishman as he, Whistler, looked like Dinkelspiel!

"I have seen plenty of Britishers," thought the young fellow, "and not
one of them ever looked like this chemist, or whatever he is. And he's a
stranger--worked here only a month.

"He was not tapping rocks or getting botanical specimens over here when
we fellows came along the Upper Road. His interest was in this dam--if
it was at long distance. I wonder if we ought to report him to the
marshal's office.

"And get him, if he's innocent of any wrongdoing, into hot water,"
Whistler added, wagging his head. "Say! that won't do. We fellows came
near getting poor Seven Knott into trouble, thinking him a German spy,"
he added, referring to an incident mentioned in "Navy Boys After the
Submarines."

Thus meditating he drew nearer to the place where the flashboard was
down and the water poured into the rocky river bed. There were stepping
stones here, so it was easy for an agile person to get across the
stream.

A blue haze of spray rose from the foaming water on the rocks, and there
sounded a pleasant murmur from the falling water. Birds darted in and
out of this spray, fluttering their pinions in the bath thus provided.

On this side of the waterfall Whistler could discover nothing on the
face of the dam nor along its foot that seemed in the least suspicious.
The masonry was perfect.

He crossed the river bed, leaping from stone to stone, and stepped up so
close to the falling water that the spray splashed him. It was somewhere
about here, he thought, that the man, Blake, had focused his field-glass
from the roadside.

There was absolutely nothing out of the way here that he could see. The
brush was kept cleared out at the foot of the dam for a dozen feet or
so; there seemed to be no cover here. Not a stone had been overturned
along this cleared path.

The water splashed and bubbled at the foot of the fall. Did it seem to
splash more vigorously just here at the edge of the pool, hidden by the
spray in part, and partly by the overhang of a great rock on which
Whistle