94-8 On the Mean Temperature of the 



Therefore, 



The first view of these tables shows that the temperature of 

 the earth, in the same latitude, is different under different meri- 

 dians ; therefore, to obtain a clear view of the phenomenon, we 

 must particularly class the observations according to the meri- 

 dians in which they fall. The observations brought forward 

 comprise four principal meridians, or rather meridional zones ; 

 that of Paris, of Umeo, of the Urals, and, lastly, of Cumana. 



Besides, some of the stations mentioned have a considerable 

 altitude above the sea; the temperature of their soil must there- 

 fore be reduced to its level. Unfortunately, we possess so few 

 observations of this kind, that it is impossible to fix with exact- 

 ness the diminution of the temperature of the earth with the al- 

 titude. We may, however, conclude fi'om these observations, 

 that the decrease of the temperature of springs is subject to 

 nearly the same law as that of the air, and that, if any difference 

 exists, the first decreases more slowly than the latter. We will, 

 therefore, in round numbers, estimate 2°.25 for 250 metres. 

 We then obtain for the temperature of the earth in Congo 77° ; 

 in Cincinnati, 55>°.Q^ ; in Geneva, 55°.17 ; in Paris, 53°.37 ; in 

 Giwartenfiall, 38°.75 ; and in Carmeaux, 58°.l. Of the ob- 

 servations in the Urals, that of Kisnekejewa must be increased 

 2°. 7, the rest 1°.8. The observations now obtain the following 

 form, classed according to the meridians just mentioned. 



" The mean temperature of the air in Slatoust (Lat. 55°) is 1°.35. 

 nekejewa is half a degree more to the south, and 70 metres lower. 



Kis- 



