CHAPTER XII 



"PHOSPHORESCENCE," OR LUMINESCENCE, IN 



THE SEA 



One of the most widespread and most commonly observed, 

 and at the same time most remarkable and mysterious, of 

 the phenomena of the ocean is the so-called " phosphores- 

 cence." Most summer visitors to the seaside and voyagers 

 in ocean liners are familiar with the diffused glow of light 

 in the water on a dark night, or the innumerable brilUant 

 sparkles seen where a wave breaks on the shore, or an oar 

 or a rope ruffles the surface, or when a coin or small stone 

 is dropped over the side of a boat and leaves the track of 

 its passage through the water illumined by points of light. 

 All this has been known from the earliest times, and there 

 are many records from observers of the phosphorescence 

 of the sea in all parts of the world, tropics and polar alike, 

 and almost as many speculations as to the cause and essential 

 nature of the phenomena observed. 



The term " phosphorescence " is unfortunate, as it is apt 

 to lead to confusion with mineral phosphorescence, while 

 the light in the sea is now known to be due solely to the 

 luminosity of certain living organisms under certain condi- 

 tions, and has no connection with the chemical element 

 phosphorus. The more correct term, made use of by 

 the most recent investigators, is " bio -luminescence," or 

 briefly the noncommittal word " luminescence " to which 

 I shall adhere in this discussion of the subject. 



The organisms producing this Hght in the sea are of many 

 kinds — both animals and plants, large and small, highly 



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