PHOSPHORESCENCE. 57 



Many philosophers thought that, at this period, 

 the earth was bathed in the tail of a comet. 



But in 1831 another dry fog exactly similar 

 was observed ; it did not spread so far as that of 

 1783, and as it did not cover the whole of Europe, 

 it was easy to perceive that no comet was present 

 to cause its production. 



The origin of these dry, luminous mists, is yet 

 a mystery. It may, however, be noted that in 

 1 783 Calabria was visited by a terrible earthquake 

 which destroyed 40,000 inhabitants ; Mount Hecla, 

 in Iceland, broke out in one of its most remark- 

 able eruptions, and volcanic rocks were seen to 

 emerge from the sea, etc. 



It is said that a periodical dry fog, which does 

 not spread over the sea, visits the eastern coasts 

 of Africa with the disastrous wind called the par- 

 matan ; but whether it is luminous or not I can- 

 not say.* 



But one of the most curious phenomena ever 

 witnessed was doubtless that described as having 

 been seen by General Sabine and Captain James 

 Ross in their first northern expedition. Being in 

 the Greenland seas during the period of darkness, 

 they were called up by the officers on deck to ob- 

 serve an extraordinary appearance. Ahead of the 

 vessel, and lying precisely in her course, appeared 



* On a dry fog observed at London, see my note in the 

 ' Comptes-Bcndus,' Paris, 1861. 



