Atmosphere and the Earth. 243 



We will compare these observations with those collected by 

 Cordier in his treatise, " Essai sur la Temperature de Tlnte- 

 rieur de la Terre," Annales du Museum d'Histoire naturcUe 

 (8. Annee, 3. Cahier) *. It is here to be observed, that, to ob- 

 tain correct results, the temperature of mines cannot be com- 

 pared with the mean temperature of the air, but only one mine- 

 station with another ; that the superior station be not too near 

 the surface of the ground ; that, finally, the lower station be at 

 a sufficient depth. If we proceed in this way, many irregulari- 

 ties vanish, which Cordier met with in comparing his observa- 

 tions. 



The last five observations may be used with some safety in 

 the determination of the increase of temperature with the depth. 

 Tlie two first exceed the other too much, to admit of their 

 being employed in the determination of the mean. Here, again, 

 dividing the sum of the differences of the depths by the sum of 

 the differences of temperatures, we obtain, as the depth corres- 

 ponding tor c, 20.2 metres,— or for 2°.25 Fah., 9,5.9,5 metres,— 

 or an increase of temperature of 8°.91 Fah., for every 100 metres ; 

 which agrees very well with the results found for Bogoslowsk. 

 " This pai>er given in former Number of this Jouinai. 



q2 



