On the Rock Art measurements - I know he was right because I've been out with my Megalithic Ruler and checked things. Ancient person was using the bent finger to mark out the designs - just as they were stepping out the circles. Watching Tibetan monks mark out their sand mandalas is instructive as they are using similar techniques, perhaps, to the rock art carvers. I've a cupmarked stone where the diameter is exactly 1MI. Arch. goons will just say it's a fossil cavity, I suspect. Will see further into the winter!