THE INDIAN OCEAN. 873 
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 
by 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- 
ning 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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