NIAGARA. 145 



first absorbed, and after them the other rays. Where, there- 

 fore, the water is very deep arid very pure, all the colors 

 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 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 muddy, by rendering the particles 

 too numerous and gross, /ouch 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 



