154 



LUMINOSITY OF THK SEA. 



pelagica, var B., and the Monophora noctiluca, which M. Bory St. Vin- 

 cent has recently discovered during the expedition of Captain Baudin. 

 The microscopic animals which Forster saw swimming in innumerable 

 multitudes on the sea, near the Cape of Good Hope, are of this number, 

 and still undefined. The luminosity of the sea is, sometimes, occasioned 

 by these living lights ; I say sometimes, as more frequently, although the 

 animals increase in size, none can be perceived in the luminous water ; 

 yet whenever the waves strike against a hard substance and disperse in 

 foam, particularly where the sea is greatly agitated, we perceive a gleam 

 of light similar to lightning. The source of this phenomenon is probably 

 the decomposed fibres of the dead mollusca, which abound in the depths 

 of the sea ; when this luminous water is strained through cloth of a close 

 texture, these fibres are sometimes separated in the form of luminous 

 dots. When we bathed at night in the Gulf of Cariaco, near 

 Cumana, some parts of our bodies remained luminous after coming out 

 of the water, the luminous fibres attaching themselves to the skin. 

 From the immense quantity of mollusca dispersed in all the seas of the 

 torrid zone, it is not astonishing that the sea should emit light, although 

 we cannot extract from it organic matter. The infinite division of the 

 dead bodies of DagyscB and Medusce, may lead us to consider the 

 entire sea as a gelatinous fluid, which consequently is luminous, has a 

 nauseous taste, is unfit to be drunk by man, but is nourishing to 

 many fish. 



If a board be rubbed with a part of the Medusa hysocella, the part 

 rubbed becomes again luminous whenever a dry finger is passed 

 over it. During my voyage from the south to America, I sometimes 

 placed a medusa on a pewter plate. If I struck the plate with 

 other metal, the least vibration of the pewter was sufficient to make 

 the animal shine. Now, I may ask, how did the shock and vibration 

 act in this case ? Did they immediately raise the temperature ? 

 Did they discover new surfaces? Or, did the shock elicit the 

 phosphoric hydrogen gas, which, coming in contact with the oxygen 

 of the atmosphere, or of the sea water, cause this appearance ? 

 The effect of a shock, which excites light, is most astonishing in 

 a troubled sea, when the waves dash against each other in all 

 directions. Between the Tropics, I have seen the sea luminous in all 

 temperatures ; but it was more so on the approach of a tempest, or, 

 when the sky was lowering, stormy, or obscured. Cold and heat 

 seem to have little influence on this phenomenon ; for on the sand- 

 banks of Newfoundland, the phosphorescence is often very strong 



