The Green Colouring of Surf on the Horizon

Abstract

ON December 16, 1920, at 5h. 30m. p.m. Central Java time, while the steamer van Noort was passing by the small island of Pisang, north of Kroë, on the western coast of Sumatra, at a distance of about 3 km., I noticed that the breakers on the shore were not white, but green. Observing the phenomenon with a binocular it was possible to see more details. The low breakers especially showed the green colour. Breakers rising higher became white, the lower right and left corners, however, remaining green. As the breaker ran forward along the shore a green corner preceded, and sometimes the separate crests seemed to be coloured. Along the shore of Sumatra, at a distance of 7 km., no particular colours could be observed. From the upper decks of the steamer the colour could be seen, but it was less intense.