Stranica 164 [164]
98 LIGHT AND WATER
projects into the shallow water. The brilliant colour
here may be partly caused by the yellow or orange
colour of the stone or shingle. A bank of pink sand
seen through the blue water sometimes shows as a
purplish streak, whilst the margin of deeper purple
at the waters edge is due to masses of seaweed and
ink-like stains on the submerged rocks. These pink
or purple-blue patches on the water can be seen al¬
most anywhere along our coasts. That rocks, which
at low tide are seen to be of a dark purple colour, or
even the darker kinds of seaweed, should give rise to
such patches seems natural enough, but it may occa¬
sion some surprise to find that they are often caused
by orange or olive-green seaweed. So different is
the natural colour of the seaweed to the delicate
“pink madder” colour that it assumes under water,
that the casual observer will hardly connect the two,
until he has satisfied himself on this point by closer
inspection (see page 110).
In very calm waters, dark lines, having almost
the appearance of shadows, are often seen stretching
across the surface in the distance; these will prove
on approach to consist of minute ripples reflecting
light from the upper sky. The water is seldom smooth
enough to reflect the lowest region of the sky. Thus
it is that the golden streak of light from the setting
sun disappears before the sun touches the horizon.
But if the sea is absolutely calm, the horizon line may
entirely disappear—an effect said to be of common
occurrence in the Mediterranean—so exactly is the
colour of the sky repeated in the water. For we owe
our usual horizon line to the fact that the ripples on