PHOSPHORESCENCE. 57 
Many philosophers thought that, at this period, 
the earth was bathed in the tail of a comet. 
But in 18351 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 Kurope, 
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 
1783 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-Rendus,’ Paris, 1861. 
