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COLOURS IN STILL WATER 71
imposed one upon the other, though, by reason of
the great difference in distance of the objects forming
them, it is not easy to look at both at once. The
clouds, being so far off, demand a different adjustment
of the eyes to that needed for the objects at his feet,
so that, on looking from one picture to the other, he
is conscious of an actual movement of the eyes. Now
if, instead of looking straight down into the water,
the line of vision be gradually inclined, the one picture
will be found to gain in strength, and the other to
fade rapidly away; in other words, the reflexion of
the sky becomes more distinct, whilst the bottom dis¬
appears. 1hus the principle illustrated in Figs. 25,
pp. 63 and 64, is verified, viz., that the more obliquely
one looks at the still surface of a sheet of water, the
. more will the eye receive of reflected and the less of
refracted rays. As the gaze is turned farther away
from the feet, the picture of the sky formed by re¬
flexion, which has the great advantage of being far the
more luminous, predominates so rapidly over the other
that at a distance of a few yards, say ten, it has entirely
supplanted it. It might be objected that the increased
depth of water would alone account for this, but the
change will be found to be just as remarkable, or very
nearly so, on looking in a direction parallel to the
shore, where the depth remains practically the same.
Exactly the same principle applies in the case of
deeper or less clear water, where, looking down at it,
we do not see the bottom, but we do see the colour
of the water. We have, as before, the picture of the
sky formed by rays reflected at the surface superim¬
posed upon the other picture, formed by rays coming