asin is enclosed by high and almost precipitous
banks--covered, at the time, with russet woods. A kind of mystery
attaches itself to gyrating water, due perhaps to the fact that we are
to some extent ignorant of the direction of its force. It is said
that at certain points of the whirlpool, pine-trees are sucked down,
to be ejected mysteriously elsewhere. The 'water is of the brightest
emerald-green. The gorge through which it escapes is narrow, and the
motion of the river swift though silent. The surface is steeply
inclined, but it is perfectly unbroken. There are no lateral waves,
no ripples with their breaking bubbles to raise a murmur; while the
depth is here too great to allow the inequality of the bed to ruffle
the surface. Nothing can be more beautiful than this sloping liquid
mirror formed by the Niagara, in sliding from the whirlpool.

The green colour is, I think, correctly accounted for in the last
Fragment. While crossing the Atlantic in 1872-73 I had frequent
opportunities of testing the explanation there given. Looked properly
down upon, there are portions of the ocean to which we should hardly
ascribe a trace of blue; at the most, a mere hint of indigo reaches
the eye. The water, indeed, is practically black, and this is an
indication both of its depth and of its freedom from mechanically
suspended matter. In small thicknesses water is sensibly transparent
to all kinds of light; but, as the thickness increases, the rays of
low refrangibility are first absorbed, and after them the other rays.
Where, therefore, the water is very deep and very pure, all the
colours are absorbed, and such water ought to appear black, as no
light is sent from its interior to the eye. The approximation of the
Atlantic Ocean to this condition is an indication of its extreme
purity.

Throw a white pebble into such water; as it sinks it becomes greener
and greener, and, before it disappears, it reaches a vivid blue-green.
Break such a pebble into fragments, each of these will behave like the
unbroken mass; grind the pebble to powder, every particle will yield
its modicum of green; and if the particles be so fine as to remain
suspended in the water, the scattered light will be a uniform green.
Hence the greenness of shoal water. You go to bed with the black
Atlantic around you. You rise in the morning, find it a vivid green,
and correctly infer that you are crossing the bank of Newfoundland.
Such water is found char