“What are those lines of foam you see on a windy lake?” the couple asked. Immediately I was transported to a vista high above a Boundary Waters lake. A stiff breeze tousled the water’s deep blue surface, which was striated with parallel lines of bubbles. The pattern was striking. Then another mental picture replaced that one: the face of my friend Sam, explaining the lines to me more than a decade ago. Unfortunately, that image no longer has a caption. What did Sam say those were called?
