240 On tlie Mean Temperature of the 



vember, enclosed in a wooden basin, scarcely two feet under the 

 surface of the ground, at the country-house of Professor Vogel, 

 at the foot of the ridge of hills which skirts the left bank of the 

 Kasanka. If we combine the observations of the 29th July and 

 19th October, as above, we obtain for the mean temperature 

 of the wells at Kasan 41°.13. 



The mean temperature of wells in Kasan is therefore about 

 2°.03 less than the mean temperature of the earth, and re- 

 semble the temperature of the atmosphere in their changes 

 being greater in the observations brought forward, and double 

 as much as the temperature of the earth. 



In Kasan, the mean temperature of the wells is a little more 

 than the mean between that of the air and earth. 



Mean Temperature of the Air in Slatoust (Lat. 55° 8', 

 Long. 51° from Paris; Elevation above the level of the 

 sea 370 metres). 



Dr Eversmann, now professor of Natural History in Kasan, 

 during the years 1817-1820, made thermometrical observa- 

 tions in Slatoust, with a thermometer, whose freezing and boil- 

 ing points were accurately adjusted. The observations of 1818 

 and 1819 are complete ; for 1817 and 1820, I calculated mere- 

 ly the means for the months of April and October. 



It would indicate the greatest cold in the morning, the 

 greatest heat about 2 p. m. ; but as these observations were not 

 made with a register-thermometer, we are not certain whether 

 the highest and lowest temperature was observed. 



Observations were also made at 12, 6, and 10 ; but as the 

 mean of the maxima and minima gives most exactly the mean 

 temperature of the year, so in the calculation of the latter no 

 regard was paid to these observations. The following table 

 contains the monthly mean : — 



