77 



derable distance ; when again the diffused luminous 

 appearance of the sappharina indicator is seen, he 

 may be certain he is in soundings, and probably at no 

 great distance from some fatal spot." * 



In terrestrial insects, peculiar organs seem to secrete 

 or treasure up the luminous matter, and transparent 

 spots permit it to be seen ; but in marine insects it 

 generally seems to pervade the entire structure. 

 Spallanzani by removing the luminous matter from 

 medusae, found that its phosphorescency was commu- 

 nicated to water and milk. He considered it a viscid 

 secretion ; but in our opinion it is owing either to the 

 eggs of the animals being luminous, or to parasitic 

 animalculse, which may be its food. Various have 

 been the conjectures entertained on the luminosity 

 of the ocean ; such as absorbed solar light, which 

 the friction of the waves has evolved ; electricity, too, 

 has been supposed an agent in the production of 

 this wonderful phenomenon ; also diffused phosphoric 

 matter ; while luminous animals have by other observers 

 been considered the cause of the phosphorescence of 

 the sea, and this last most rational opinion seems now 

 fully substantiated. 



An anonymous writer in Mr. Loudon's Magazine of 

 Natural History f, says that the idea of the phos- 

 phorescence of the sea being the presage of a storm 

 has been long entertained among sailors, and in this 

 case they should be the best judges whether the event 

 proves it so : he continues to observe, that it may be 

 seen all the year round in the Caribbean Seas, where 

 there are no storms but in the hurricane months. 

 This may be the case there, but may not be so else- 

 where : we did not talk of the absence altogether, but 



* Page 50. t Vol. i. p. 304. 



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