Oldal 159 [159]
OCR
COLOURS IN RIPPLED WATER 93 colour of the sea near the shore, is, as we have said, green, and in one spot, where the water is in movement, the ripples on the surface show, as has been explained, this green to the eye. Close by there may be a portion of still water, sheltered by a ledge of rocks, and in this the smooth surface, reflecting the blue sky and showing little or no local colour, serves to emphasize the greenish tint which the neighbouring water, in virtue of its ripples, is displaying. A violent gust of wind, suddenly striking a nearly calm surface, brings out the colour of the water to a still greater extent, owing to the greater steepness of the minute waves to which it gives rise. When little waves are lapping on the smooth sand, it is the colour of the sand, rather than of the water, too shallow to show any colour of its own, that we see in the upturned surfaces. Here the difference of colour between the near and far sides of the waves is very plainly seen, the latter showing nothing of the colour of the sand beneath them, but only reflected blue from the sky. In shallow estuaries a delightful variety of colour is caused in this way in sunny weather. In the strongly rippled surfaces, wherever the water is turbid or very shallow, it shows the pink colour of the sand, and where it is deeper and clearer (but still strongly rippled) it looks a bright green ; whilst the smoother parts of the water, seen obliquely, show only sky reflexion. We have here a notable illustration of the principle we are discussing, viz., the increased power of seeing zz¢o water that we obtain by looking more abruptly at its surface. When a stiff breeze is blowing straight into a shallow sandy
