It was a bell, a fallen bell, and the place before him must have been a chapel.

He remembered that an Armenian monastery had been marked on the big map, and he guessed it was the burned building on his right.
The thought of a chapel and a bell gave him the notion of some human agency.

And then suddenly the notion was confirmed.

The sound was regular and concerted--dot, dash, dot--dash, dot, dot.

The branch of a tree and the wind may play strange pranks, but they do not produce the longs and shorts of the Morse Code.
This was where Peter's intelligence work in the Boer War helped him.
He knew the Morse, he could read it, but he could make nothing of the signalling.