I don't think it's thermal Steve, otherwise how can some dowsers date artifacts? One I heard of recently dated 3,000 artifiacts and had her date verified on 80% of them. Don't ask me. I can't even dowse, but thermals sound like a blind alley. After all we'd be twitching all over the place, the local environment changes all the time based on wind, clothing etc. No dowser has ever said it was easier nude!