adow is thrown across a space of water of
strong local color, receiving, alternately, light and dark reflections,
it has no power of increasing the reflectiveness of the water in the
bright spaces, still less of diminishing it; hence, on all the dark
reflections it is seen more or less distinctly, on all the light ones it
vanishes altogether.

Let us take an instance of the exquisite complexity of effect induced by
these various circumstances in co-operation.

Suppose a space of clear water showing the bottom under a group of
trees, showing sky through their branches, casting shadows on the
surface of the water, which we will suppose also to possess some color
of its own. Close to us, we shall see the bottom, with the shadows of
the trees clearly thrown upon it, and the color of the water seen in its
genuineness by transmitted light. Farther off, the bottom will be
gradually lost sight of, but it will be seen in the dark reflections
much farther than in the light ones. At last it ceases to affect even
the former, and the pure surface effect takes place. The blue bright sky
is reflected truly, but the dark trees are reflected imperfectly, and
the color of the water is seen instead. Where the shadow falls on these
dark reflections a darkness is seen plainly, which is found to be
composed of the pure clear reflection of the dark trees; when it crosses
the reflection of the sky, the shadow of course, being thus fictitious,
vanishes.

Farther, of course on whatever dust and other foulness may be present in
water, real shadow falls clear and dark in proportion to the quantity
of solid substance present. On very muddy rivers, real shadow falls in
sunlight nearly as sharply as on land; on our own sea, the apparent
shadow caused by increased reflection, is much increased in depth by the
chalkiness and impurity of the water.

Farther, when surface is rippled, every ripple, up to a certain variable
distance on each side of the spectator, and at a certain angle between
him and the sun, varying with the size and shape of the ripples,
reflects to him a small image of the sun. Hence those dazzling fields of
expanding light so often seen upon the sea.

Any object that comes between the sun and these ripples, takes from them
the power of reflecting the sun, and in consequence, all their light;
hence any intervening objects cast apparent shadows upon such spaces of
intense force, and of the exact shape, and in the exact place of rea