Dowsing at Mouse Castle

I went back up to Mouse Castle over the weekend, on a lovely day with just a hint of rain in the air. It was the Pagan festival of Lammas, or Lughnasadh, celebrating the beginning of the harvest season traditionally. So I thought that mucking about with a dowsing pendulum would be an appropriate thing to do. I also took the heel of a loaf with me - lammas means "loaf mass" and it's a traditional offering. I left it by the spring.
Up on top of the hill, I studied my notes from the British Dowsers Society (www.britishdowsers.org), which recommend that you first ask permission to dowse of the Spirit of the Place. Since the pendulum started swinging in a circle, I reckoned I was good to go, so I went round to the north of the castle site, where we'd picked up 'unusual vibrations' before, and had a go.
According to TC Lethbridge's experiments (I found the list I'd copied out of his book about twenty years ago, as well as tracking down a list online) a 40 inch long string should give a reading for the direction north, and so it proved. From swinging back and forth in a straight line, the pendulum started to swing in a circle. Then I shortened the string to see what else I could pick up. There was nothing for water (26 and a half inches), and I didn't see the point of trying for concrete or glass or the colour purple - but there was a very strong reaction for what TC Lethbridge labelled as "psychic potential". What that may mean, I'm not sure, but it was very definite.
I wondered if there would be any reaction if I moved round to the other side of the castle mound - in case there was a line running back towards Cusop Hill to the south - but the results round there were wishy washy at best. I just about got a reading for "south" (20 inches).
I also noticed that a fox has been using an old tree stump to mark his territory - fox poo is quite distinctive.
So that was all interesting, and a good excuse to make the walk up to the hill again - but I'm not sure that it tells me anything more about the earthworks there.