210 I'HOSPIIOIlErfCENCE OF THE SEA. 



nous at considerable depths beneath the surface. 

 Near the mouth of the Plata some circular and oval 

 patches, from two to four yards in diameter, and with 

 defined outlines, shone with a steady but pale light; 

 while the surrounding water only gave out a few 

 sparks. The appearance resembled the reflection of 

 the moon, or some luminous body ; for the edges 

 were sinuous from the undulations of the surface. 

 The ship, which drew thirteen feet of water, passed 

 over without disturbing these patches ; therefore 

 we inust suppose that some animals were congre- 

 gated together at a gi-eater depth than the bottom 

 of the vessel. 



Near Fernando Noronha the sea gave out light in 

 flashes. The appearance was very similar to that 

 which might be exj^ected from a large fish moving 

 rapidly through a luminous fluid. To this cause 

 the sailors attributed it ; at the time, however, I 

 entertained some doubts, on account of the fre- 

 quency and rapidity of the flashes. I have already 

 remarked that tlie phenomenon is very much more 

 common in warm than in cold countries ; and I 

 have sometimes imagined that a disturbed electrical 

 condition of the atmosphere was most favourable 

 to its production. Certainly I think the sea is most 

 luminous after a few days of more calm weather 

 than ordinary, during which time it has swarmed 

 with various animals. Observing that the water 

 charged with gelatinous particles is in an impure 

 state, and that the luminous appearance in all com- 

 mon cases is produced by the agitation of the fluid 

 in contact with the atmosphere, I am inclined to 

 consider that the phosphorescence is the result of 

 the decomposition of the organic particles, by which 

 process (one is tempted almost to call it a kind of 

 respiration'^ the ocean becomes puiified. 



