Slicks, or calm streaks on a rippled sea, are often seen on co11Btal waters and lakes when the wind is light. They are formed by the ripple-damping action of a surface film of organic matter which occurs naturally on biologically productive waters. The ability of films to damp ripples varies radically with the degree of compaction of the film molecules. Such compaction may be caused by horizontally convergent flow in the water surface or by horizontal convergence of the wind stress....