We found this interesting pattern in a gill high above Hayeswater. It looked at first as if it would be due to stationary waves. But in the end it seemed more like a beach tide line pattern. It was very stable: we threw in a stone and the ripples on the water moved through the pattern (see below). The hole seemed to close up. Perhaps it is some kind of surface tension effect. It occured to me that there might be molecules with hydrophilic and hydrophobic ends lining up. I have no clear explanation.
