Oldal 159 [159]
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 move¬
ment, 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 neighbour¬
ing 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