071 SuUerraiieah Temperatures. 291 



decompositions capable of producing a certain degree of heat ; 

 but these cases must be very rare. According to the above, the 

 following table, containing thirteen observations made in Saxony, 

 France, England, and Mexico, may be consulted, as presenting 

 useful documents, although no absolute result can be deduced 

 from them, with reference to the subject in question. 



TABLE of Observations made on the TeiAperature of Puis- 

 ards (or waste wells) in Mines. 



According to this table, the depth corresponding to the in- 

 crease of 1° Fahr. of temperature would be in round numbers as 

 follows : By four observations made in three mines in Saxony, 

 from 102 to 64 feet, mean 83 feet ; by three observations at 

 Poullaouen, from 351 to 82 feet, mean 206 feet ; by four obser- 

 vations at Huelgoet, from 90 to 36 feet, mean 57 feet ; by one 

 observation at Dolcoath, 45 feet ; and by one observation made 

 at Guanaxuato, 46 feet. 



(To be concluded in next Number.) 



T 2 



