VIII. 



TABLES 



FOR COMPUTING DIFFERENCES OF ELEVATION FROM BAROMETRICAL OBSERVATIONS, 



BY E. PLANTAMOUR. 



[These Tables, computed by Professor E. PLANTAMOUR, Director of the Observatory at Geneva, 

 Switzerland, are found in Vol.. XIII. Part 1, of the Memoires de la Socie'te de Physique, frc. de Geneve, 

 p. 63, together with the following explanations.] 



IN No. 356 of the Astronomische Nachrichten, Bessel published a paper on the 

 measurement of heights by means of the barometer, in which he deduces a formula 

 which contains a factor depending on the humidity of the air. This formula is : 



' HP. 0.002561 0.0279712 T-. 0.0000625826 T 



. . 



7 " 



f ] 



where the various quantities have the following signification : 



h being the elevation of the lower station, and 



h 1 the elevation of the upper station above the level of the sea, 



a = the radius of the Earth, 



IT' 



= 



P = the weight of the atmosphere at the lower station, 

 P' =. the weight of the atmosphere at the upper station, 



the unit of weight assumed being the pressure of a column of mercury 



72 



