Oil Svlderraiiemi Temperaiui^e. 



TABLE of Observations made on the Temperatare of the Water 

 ofPuisards or En.gine-jnis in Mines. 



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

 crease of 1° of heat would be, in round numbers, as follows: 

 By six observations made in four mines of Cornwall, from 37 

 to 27 feet, mean 32 feet ; by three observations made in three 

 mines of Devonshire, from 71 to 35 feet, mean 60 feet ; by one 

 observation at Bex, 48 feet ; and by two observations at Poul- 

 laouen, from 137 to 95 feet, mean 116 feet. 



3dly, It cannot be disputed that the waters which remain 

 stagnant in mines under the form of great inundations, or true 

 subterranean lakes, are well adapted to give very approxima- 

 tive indications with reference to the object in view. The ol)ser- 

 vations of this description generally lead to results lower than 



• This mean temperature is approximative, and probably a maximum. 

 Knowing the places, I have concluded it from the ftrflowing data : Mean tem- 

 perature of Zurich, 47°.8, for six years, Escher and Wahlenberg ; ditto of 

 Coire, 48°.6, for four years, Sails and Wahlenberg; ditto of Geneva, 49'.3 



The other means of my four tables are those which the authors of the ex- 

 periments have indicated. I shall speak of their merit afterwards. 



c2 



