242 Mr C. Martins on the Nature and Origin of 



thrown up sixteen miles from the coast of Iceland, still 

 emitted flames in February 1784. 



If we compare these facts with the dates of the appearance 

 of the dry fog, we will observe a very remarkable agreement. 

 The first appearance was at Copenhagen, on the 24th May, 

 precisely at the time when the ground of Iceland began to 

 emit smoke, gases, and vapours, phenomena which were pre- 

 cursors of the eruptions and earthquakes about to succeed. 

 It was likewise at Copenhagen that the fog continued longest. 

 From Copenhagen it extended to France, Germany, and 

 Italy, where it was remarked almost everywhere from the 

 16th to 18th June. At the end of the month it was observed 

 in the south, in Portugal and Syria ; in the east, at Moscow 

 and Buda in Hungary. This general progress from north 

 to south, and from east to west, leads us to seek for the 

 origin of this fog in the north-west of Europe, precisely 

 where we find Iceland, the permanent theatre, throughout 

 the whole summer of 1783, of a true burning of the earthy 

 as it was called by cotemporary authors. 



The dry fog, or rather smoke, which covered Europe dur- 

 ing the summer of 1783, was therefore owing to volcanic 

 eruptions and combustions which took place in Iceland, and 

 perhaps to the earthquakes which laid waste Calabria. The 

 rarity of the phenomenon is explained by the rare occur- 

 rence of eruptions so continuous and important as those 

 which ravaged these two countries. For sixty- seven years 

 meteorologists have not observed a fog so general and per- 

 manent in Europe, and for the same period no eruptions have 

 happened comparable to those of 1783. But this example 

 proves to us that dry fogs, of a local character, observed at 

 great distances from any active volcano, may be connected 

 with eruptions, and the combustion of the vegetables which 

 cover the soil enveloped in burning lava. In this point of 

 view, the fogs formed by the ashes and smoke of volcanoes 

 enter into the category of those which are owing to the com- 

 bustion of peat-grounds in Westphalia. Both originate in 

 extensive conflagrations ; both are produced, not by water, 

 but by fire ; and both are completely different from the fogs 

 formed by aqueous vapour. 



