The eye of Capelaw?

On the summit of Capelaw there is an iron post with two sides (or plates). At eye level there is a circular hole in both sides. I've no idea what the purpose of this post used to be, but it makes a good marker for the top of the hill. It was bright and sunny when Ian and I were there this afternoon and so I've tried to capture the sun through the "eye".

Many thanks for all your good wishes for yesterday's race. I'm so please I finished :o)