THE INDIAN OCEAN. 373 



Ocean, than the whole surface is seen to be, as it were, 

 composed of light, assuming, however, various forms 

 and aspects. The most usual appearances, as far as 

 they have fallen under my own observation in the 

 Atlantic, are as follows: On looking over the stern, 

 when the ship has steerage- way, her track is visible 

 bv a line or belt of light, not a bright glare, but a 

 soft, subdued yellowish light, which immediately 

 under the eye resembles milk, or looks as though the 

 keel stirred up a sediment of chalk which diffuses 

 itself in opaque clouds through the neighbouring 

 water, only that it is light and not whiteness. 

 Scattered about this cloudiness, and particularly 

 where the water whirls and eddies with the motion 

 of the rudder, are seen innumerable sparks of light 

 distinctly traced above the mass by their brilliancy, 

 some of which vanish and others appear, while others 

 seem to remain visible for some time. Generally 

 speaking, both these phenomena are excited by the 

 action of the vessel through the waves, though a few 

 sparks may be observed on the surface of the waves 

 around. But now and then, when a short sea is run- 

 nine without breaking waves, there are seen broad 

 flashes of light from the surface of a wave, coming 

 and going like sudden fitful flashes of lightning. 

 These may be traced as far as the sight can reach, 

 and in - their intermittent gleams are very beautiful : 

 they have no connection with the motion of the ship. 

 In a voyage to the Gulf of Mexico, I saw the water 

 in those seas more splendidly luminous than I had 

 ever observed before. It was indeed a magnificent 



sight, to stand in the fore part of the vessel and 



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