NIAGARA. 145 
first absorbed, and after them the other rays. Where, there- 
fore, the water is very deep and very pure, all the colors 
are absorbed, and such water ought to appear black, as no 
light is sent from itsinterior 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 charged with fine matter in a state of 
mechanical suspension. The light from the bottom may 
sometimes come into play, but it is not necessary. A storm 
can render the water rnuddy, by rendering the particles 
too numerous and gross. Such a case occurred toward the 
close of my visit to Niagara. There had been rain and 
storm in the upper lake-regions, and the quantity of sus- 
pended matter brought down quite extinguished the fasci- 
nating green of the Horseshoe. 
Nothing can be more superb than the green of the 
Atlantic waves, when the circumstances are favorable to 
the exhibition of the color. As long as a wave remains 
unbroken no color appears; but when the foam just doubles 
over the crest, like an Alpine snow-cornice, under the cor- 
nice we often see a display of the most exquisite green. It 
is metallic in its brilliancy. But the foam is necessary to 
its production. The foam is first illuminated, and it scat- 
ters the light in all directions; the light which passes 
through the higher portion of the wave alone reaches the 
eye, and gives to that portion its matchless color. The 
folding of the wave, producing as it does a series of longi- 
tudinal protuberances and furrows which act like cylindrical 
lenses, introduces variations in the intensity of the light, 
and materially enhances its beauty. ^* / 
We have now to consider the genesis and proximate 
