PHOSPHORESCENCE. 55 



son, who states that during a storm on the 30th 

 July, 1797, at about five in the morning, certain 

 clouds were observed to shine first with a red, and 

 afterwards with a blue, light. 



De Luc affirms also, that one winter's night, in 

 the neighbourhood of London, he observed a lumi- 

 nous cloud extending east and west across the 

 southern meridian of the place, about 30 or 40 

 degrees from the zenith. The atmosphere was 

 clear but not cold, and "there were no signs of 

 electricity/'* 



One of the most authentic and curious observa- 

 tions of luminous fogs was lately communicated in 

 a letter to M. Elie de Beaumont by M. L. F. 

 Wartmann,f of Geneva. The strange phenomenon 

 was observed during nine successive foggy nights, 

 from the 18th to the 26th of November, 1859. The 

 moon being new, was invisible and absent from 

 the heavens of Geneva. But a vast fog, not damp 

 enough to wet the earth, but so opaque as to 

 render invisible the borders of the river Leman 

 and the mount Salese, hovered permanently over 

 Geneva and its environs. This fog diffused so 

 much phosphoric light, that M. Wartmann could 

 easily distinguish books, etc., upon his table, with- 



* For more ample details on some of these phenomena, see 

 Beccaria, ' Dell' Elettricismo terrestre atmosferico;' Deluc, 'Idees 

 sur la Meteorologie,' and Arago, in the 'Annuaire' for 1838. 



f Comptes-Kendus of the Academy of Sciences, Paris, 25 De- 

 cember, 1859. 



