ILLUSTRATIONS (5). PHOSPHORESCENCE OF THE OCEAN. 249 



no indications of electricity through the smallest intervening 

 stratum of flame. 



The considerations which we have here developed render it 

 probable that one and the same process operates, alike in the 

 smallest living organisms invisible to the naked eye, in the 

 contests of the serpent-like Gymnoti, in the flashing luminous 

 Infusoria which impart such glorious brilliancy to the phospho- 

 rescence of the sea, in the thunder- cloud and in the terrestrial 

 or polar light (the silent magnetic flashes), which, caused 

 by an increased tension of the interior of the earth, are 

 announced, for some hours previously, by the sudden variations 

 of the magnetic needle.* 



Sometimes one cannot, even with high magnifying powers, 

 discover any animalcules in the luminous water; and yet, 

 wherever a wave breaks in foam against a hard body, and, 

 indeed, wherever water is violently agitated, flashes of light 

 become visible. The cause of this phenomenon depends 

 probably on the decomposing fibres of dead Mollusca, which 

 are diffused in the greatest abundance throughout the water. 

 If this luminous water be filtered through finely woven cloths, 

 the fibres and membranes appear like separate luminous 

 points. When we bathed at Cumana, in the gulf of Cariaco, 

 and walked naked on the solitary beach in the beautiful 

 evening air, parts of our bodies remained luminous from the 

 bright fibres and organic membranes which adhered to the 

 skin, nor did they lose this light for some minutes. If we 

 consider the enormous quantity of Mollusca which animate 

 all tropical seas, we can hardly wonder that sea-water should 

 be luminous, even where no fibres can be visibly separated 

 from it. From the endless subdivision of the masses of dead 

 Dayysce and Medusa the whole ocean may, in fact, be 

 regarded as a fluid containing gelatine, and, as such, luminous 

 and of a nauseous taste ; unfit for the use of man, but capable 

 of affording nourishment to many species of fish. On rubbing 

 a board with a portion of the Medusa hysocella, the surface thus 

 rubbed recovers its phosphorescence when friction is applied 

 by means of the dry finger. During my voyage to South 

 America I occasionally placed a Medusa on a tin plate, and I 

 then observed that if I struck the plate with another metallic 



* See my letter to the editor of the Annalen der Physik und 

 Cliemie, bd. xxxvii. 1836, H. 242244. 



