202 COSMOS. 



in the Earth leads us by analogy to the remarkable process 

 exlu'bited in Venus. The portion of this planet which is not 

 illumined by the Sun often shines with a phosphorescent light 

 of its own. It is not improbable that the Moon, Jupiter, and 

 the comets shine with an independent light, besides the re- 

 flected solar light visible through the polariscope. Without 

 speaking of the problematical but yet ordinary mode in which 

 the sky is illuminated, when a low cloud may be seen to shine 

 with an uninterrupted flickering light for many minutes to- 

 gether, we still meet with other instances of terrestrial develop- 

 ment of light in our atmosphere. In this category we may 

 reckon the celebrated luminous mists seen in 1783 and 1531 ; 

 the steady luminous appearance exhibited without any flick- 

 ering in gieat clouds observed by Pwozier and Beccaria ; and 

 lastly, as Arago* well remarks, the faint diffused light which 

 guides the steps of the traveler in cloudy, starless, and moon- 

 less nights in autumn and winter, even when there is no snow 

 on the ground. As in polar light or the electro-magnetic 

 storm, a current of brilliant and often colored light streams 

 through the atmosphere in high latitudes, so also in the torrid 

 zones between the tropics, the ocean simultaneously develops 

 light over a space of many thousand square miles. Here the 

 magical effect of light is owing to the forces of organic nature. 

 Foaming with light, the eddying waves flash in phosphores- 

 cent sparks over the wide expanse of waters, where every scin- 

 tillation is the vital manifestation of an invisible animal world. 

 iSo varied are the sources of terrestrial light ! Must we still 

 suppose this light to be latent, and combined in vapors, in 

 order to explain Moser's images 'produced at a distance a 

 discovery in \yhtch reality has hitherto manifested itself like 

 a mere phantom pf the imagination. 



As the internal heat of our planet is connected on the one 

 hand with the generation of electro-magnetic currents and 

 the proceas of terrestrial light (a consequence of the magnetic 

 storm), it, on the other hand, discloses to us the chief source 

 of geognostic phenomena. We shall consider these in their 

 connection with and their transition from merely dynamic dis- 

 turbances, from the elevation of whole continents and mount- 

 ain chains to the development and effusion of gaseous and 



* Arago, on the dry fogs of 1783 and 1831, which illuminated the 

 night, in the Annuairedn Bureau des Longitudes, 1832, p. 246 and 250; 

 and, regarding extraordinary luminous appearances in clouds without 

 Htorms, see NHrp.x *nr hi Tonnerrf. in the Anntiaire pour Can. 1838 

 p. k j79-28'. 



