254 M. KupfFer on Iso-geothermal Lines. 



therefore be arranged under four meridional zones, depending 

 on the meridians of Paris, Umeo, Ural, and Cumana. 



Besides, among the stations on the table, there are seve- 

 ral at a very considerable height above the sea, so that we 

 must reduce their geothermal temperature to the level of the 

 sea. Unfortunately we possess so few observations of this 

 kind, that it is impossible to determine with accuracy the di- 

 minution in the temperature of the ground which corresponds 

 with a given elevation. Our author, however, concludes, that 

 the decrease in the temperatures of springs follows the same 

 law as that of the atmosphere, or, if there is a difference, that 

 it is less rapid in the former than in the latter case. He there- 

 fore uses 1° of Reaumur for every 250 metres. By applying 

 this correction, and distributing the places into zones, he ob- 

 tains the following tables. 



First Meridian of 0° 



Third Meridian of 60° East. 



Kisnekejewa, 54° 30^ 4°.7 



Nishney-Tagilsk, 58 3 1 



Werchoturia, 59 2 7 



Bogoslowsk, 60 2 .3 



