By the time we launched from Achnacloich, on the south shore of Loch Etive, the sun had set. With the approach of night, a layer of cloud flooded the sky from inland and the summit of Ben Cruachan was lost from view.After a while, I turned round to see where Jim W was. I was amazed to see that the sun, which was by now well below the horizon, was illuminating the advancing edge of cloud in a