204 FRAGMENTS OF SCIENCE 



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 New- 

 foundland. 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 neces- 

 sary. A storm can render the water muddy, by render- 

 ing 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 suspended matter brought down quite 

 extinguished the fascinating 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, un- 

 der the cornice we often see a display of the most exqui- 

 site green. It is metallic in its brilliancy. But the foam 

 is necessary to its production. The foam is first illumi- 

 nated, and it scatters 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 



