410 



yiii. 



TABLES 



FOR COMPUTING DIFFERENCES OF ELEVATION FROM BAROMETRICAL OBSERVATIONS, 

 BASED ON BESSEl's FORMULA. 



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 Me'inoires de la Socie'te de Physique, ^~c. 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 : 



, P fo-VH' — Hr, 0.002561 ,^ 0.0279712 T — 0.0000625826 Xn 



log f = t(i + K Ty [ 1 - " -y-pp- • "• . J ' 



where the various quantities have the following signification : — • 



h being the elevation of the lower station, and 

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

 a =; the radius of the Earth, 

 a h 



H 

 H' 



a + A' 



a h' 

 a +T' ' 



P r= 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 

 D 70 



