ON THE LUMINOSITY OP THE SEA. 467 



Whether the luminous phenomenon is to be as- 

 cribed to electric energies, or an effect connected 

 with nervous influence, or dependent on something 

 peculiar and insulated from these, is a question 

 which has not yet been determined, nor perhaps 

 can be, in the present state of human knowledge. 

 Experiment seems, however, to decide, that glow- 

 worms are not more luminous in oxygen than in 

 atmospheric air ; neither is the luminosity extin- 

 guished in carbonic acid gas. This would appear 

 to countenance the belief, that it is not connected 

 with any thing like combustion. When Mr Mac- 

 cartney applied electrical stimuli, he succeeded in 

 inducing light in the case of the Lampyris ; but 

 the concomitant circumstances clearly proved, that 

 its action was entirely mechanical. 



The light of the sea has been ascribed to various 

 causes. To phosphorescence, — the effect of animal 

 decomposition, — to the imbibing of solar light, ana- 

 logous to the diamond, — and to an electric effect in- 

 duced by friction. While others have more plau- 

 sibly assigned it to the presence of luminous ani- 

 mals ; and of these, the Cancer fulgens, Medusa 

 pellucens, hemispherica, &c. TJmulus noctilucus, 

 Salpce, &c. have been described. 



I remember to have taken up a luminous medusa 

 on the coast of Norfolk, where the river New dis- 

 embogues itself into the sea. 



On my voyage from Leghorn to Civita Vecchia, 

 I remarked, that the Mediterranean was particular- 



Gg 2 



