mechanical contrivance not yet placed.

Whistler returned the flat rock back to its former position, and moved
slowly back from the place on hands and knees. Then he stood up and
looked all around to see if he had been observed. Particularly did he
look through the break in the trees toward the spot where Blake, the
stranger, had stood when Whistler and his friends had first spied him.

There was nobody in sight as far as the young fellow could see. He moved
back into the shelter of a clump of brush. He heard an automobile
chugging up from the village and believed Al and the others were
approaching the bridge where he had asked his chum to wait for him.

But he lingered a bit. He was deeply moved by his discovery. This was no
boy's plaything. The mechanism was the effort of a mature mind, perhaps
the result of inventive genius of high quality.

Some inventor might be secretly experimenting with water power here; and
if Whistler told of his discovery he might be doing the unknown a grave
wrong.

Yet Blake's peculiar actions and the fact that the foot of the dam had
been chosen for the experiment troubled the young fellow vastly.

There was nothing along the wall, as far as he could see, or upon its
face, that excited Whistler's further suspicion. Just that little water
wheel under the rock whirling and splashing by the power of the falling
stream. It was perfectly innocent in itself; yet Philip Morgan had never
been more excited and troubled in his life.