232 M. C. Martins on the Nature and Origin of 



In countries where these agricultural processes are un- 

 known, an atmospheric origin is assigned to the dry fog. In 

 order to obtain evidence of the truth, M. Egen has connected 

 the directions of the wind with the indications of the dry fog 

 for the years between 1821 and 1827, and in reference to the 

 following cities: — Aurich, Emden, Groettnigen, Meppen, 

 Lingen, Bentheim, Stadtlohn, Minden, Munster, SalzufFeln, 

 Detmold, Blomberg, Arnheim, Hamm, Paderborn, Lippstadt, 

 Aix-la-Chapelle, Elberfeld, Coblence, Brest, Paris, Stras- 

 bourg, Texel, Halle, Altona, Bielefield, Cleve, Solingen, 

 Berleburg, Osnabruck, Scest, Hildburghausen, Gotha, 

 Carlshafen, Goettingen, Treves, Brussels, Amsterdam, Essen, 

 Cologne, Brunswick, Lunebourg, Reval, and Falmouth. 



From these numerous observations, M. Egen draws the 

 following conclusions : — 



1. This dry fog is the smoke arising from the combustion 

 of peat. It has a particular smell which is always recog- 

 nised when it has once been felt. 



2. Formerly less peat was burnt than at present, and the 

 fog was less common. In the middle of the last century only 

 two days of dry fog were reckoned on annually at Lingen- 

 sur-Ems, but now they amount to eighteen. 



3. The more remote we are from the peat district, the 

 rarer they become. Thus at Lingen eighteen are observed 

 every year; at Scest. six or seven ; a day's journey further 

 away, only four or five. 



4. The intensity of the fog likewise diminishes the fur- 

 ther we remove from the peat bogs. In Eastern Friesland, 

 it is as opaque as the thickest moist fog ; at Scest, situate 

 11 myriametres from the southern border of the peat region, 

 we may always distinguish objects at the distance from 60 

 to 100 metres. It is seldom that the clouds cannot be seen, 

 and the sun does not become invisible until it reaches the 

 horizon ; at the distance of 35 myriametres from the 

 peat deposits the smoke becomes only a light bluish vapour 

 which spreads along the plains and valleys rather than on 

 the mountains, because it rests on the ground. 



5. The wind blows almost always from the peat-fields 

 to the place where the fog is seen. At Emden, it comes by 



