looked fair
down upon, it was of almost inky blackness--a solid dark
blue qualified by a trace of purple or violet. Under these
favorable conditions, the appearance presented was not unlike
that of the liquid in a vast natural dyeing-vat.

A clouded state of the sky, as was to be expected, produced
the well-known effects due to the diminished intensity of
light; the shades of blue became darker, and, in extreme
cases, almost black-blue. According to our observations,
the obscurations of the sky by the interposition of clouds
produced no other modifications of tints than those due to
a diminution of luminosity.

In places where the depth is comparatively small and the
bottom is visibly white, the water assumes various shades
of green; from a delicate apple-green to the most exquisite
emerald-green. Near the southern and western shores of the
Lake, the white, sandy bottom brings out the green tints very
strikingly. In the charming _cul-de-sac_ called "Emerald
Bay," it is remarkably conspicuous and exquisitely beautiful.
In places where the stratum of water covering white portions
of the bottom is only a few meters in thickness, the green hue
is not perceptible, unless viewed from such a distance that
the rays of light emitted obliquely from the white surface
have traversed a considerable thickness of the liquid before
reaching the eye of the observer.

The experiments with the submerged white dinner-plate,
in testing the transparency of the water, incidentally
manifested, to some extent, the influence of depth on the
color of the water. The white disk presented a bluish-green
tint at the depth of from nine to twelve meters; at about
fifteen meters it assumed a greenish-blue hue, and the blue
element increased in distinctness with augmenting depth,
until the disk became invisible or undistinguishable in the
surrounding mass of blue waters. The water intervening between
the white disk and the observer did not present the brilliant
and vivid green tint which characterized that which is seen in
the shallow portions of the Lake, where the bottom is white.
But this is not surprising, when we consider the small amount
of diffused light which can reach the eye from so limited a
surface of diffusion.

In studying the chromatic tints of these waters, a hollow
pa