246 On the Mean Temperature of the 



indicated 41°. A well there, whose surface was almost close un- 

 der the surface of the ground, was 41°.56 ; a similar well in 

 Nishney-turins (Lat. 58°|), 41°.45 ; another in Nishney-tagilsk, 

 9 feet deep, 39°. 42 ; a bore hole in Bogoslowsk, 42°.o7 ; a re- 

 servoir of water, which was filled by a small spring, and whose 

 level was very little under the surface of the earth, in the same 

 place, 41°. 



I may be permitted to quote an observation which Dr Erman 

 communicated to me, and which may confirm the observations 

 at Bogoslowsk. He found near Perm (Lat. 60°) the tempera- 

 ture of the mine- water, at 30 metres, =36°.5, which gives 36°.05 

 for the depth of 25 metres. Perm lies nearly as high as Bogos- 

 lowsk, and besides farther west : the temperature of the earth 

 there, must therefore be a little higher than that of Bogos- 

 lowsk. 



Conclusions. 



We see from the foregoing, that the temperature of the earth 

 is sometimes very different from the mean temperature of the air, 

 and its distribution follows different laws. Wahlenberg's obser- 

 vations have long ago shown (and the preceding confirm it), that 

 the temperature of springs in high latitudes is higher than that 

 of the air. Von Humboldt, and after him Von Buch, found the 

 temperature of springs, in low latitudes^ considerably lower'than 

 that of the air. We shall here give a comparative view of the 

 principal of these observations, in which only those are used 

 which are made at the level of the sea, or not much above 

 1500 feet above it. Observations on springs were preferred to 

 those on wells. The greater part is extracted from Von 

 Buch's Treatise on the Temperature of Springs, in Poggendorf's 

 Annals, vol. xii. part 3. 1828, and also from Humboldt's Trea- 

 tise on Isothermal Lines. 



