The thought was not a pleasant one.
He waited, himself crouched now behind a jutting fragment of rock, and thought he saw the object move.

A little later the sun, sliding farther down the sky, reflected a glittering something just above that rock.

A bit of glass would do that--the lenses of a field glass, for instance.

Two lenses would shine as one, Johnny believed, and was thankful that his slope was in shadow.
Taking it for granted that some one was watching the valley, he studied the spot where the glitter had already winked out--possibly because the man had moved the field glasses, sweeping the valley.

It was a good place for a spy, Johnny admitted.