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90 LIGHI AND WATER
oloomy colour, assuming in response a dark and
threatening aspect. It sometimes happens that there
is a high bank of dark clouds rising up Írom the
horizon, and overhead a lighter region, in which case
the less common effect of the rippled surface appear¬
ing lighter than the smooth may be given. ‘lowards
sunset, in the same way, the oily-looking streaks of
smooth water in a very calm sea often appear yellow
or orange by contrast with the more rippled—and
therefore bluer—surface surrounding them, reflecting,
as they do, a lower part of the sky where warmer
tones predominate. Plates XX XVIII and XXXIX
are photographs illustrative of this point. In the
upper view, taken at the narrow mouth of a West
Highland loch, the tide is flowing rapidly in a strong
current from the left. The wind (also from the west)
ruffles the mass of the water, but leaves the surface
of the current, travelling in the same direction as it¬
self, comparatively smooth. So that, while the greater
part of the water reflects ‘the sky, the path of the
current reflects the hillside and thus becomes con¬
spicuous as a dark stream winding its way through
the lighter ripple. There is also a patch of smoother
and therefore dark-looking water under the lee of the
island on the left. The lower view shows an effect of
the same nature, but with the opposite result. The
whole surface of the water is ruffled, some parts of it
more than others. In this case the smoother portion
reflects chiefly light from the low bright region of the
sky, whilst the rougher portion reflects the darker
clouds above.
But, in addition to this effect, we have the further