1865.] Pendulum Base Observations for India. 



TABLE IV. (continued.) 



435 



Determination of the Constant C f from the above Mean Results. 



E. The reduction of the resulting number of vibrations to the sea-level 

 is calculated from 



where E is the earth's radius at the latitude of the Kew Observatory, h 

 the height of the receiver above the mean level of the sea, and x a quantity 

 which, with Dr. Young, may be assumed for a tract of level country to be 

 = 666 (vide Phil. Trans, for 1819, page 98). 



This correction has been only applied to the ultimate mean number of 

 vibrations of each pendulum. 



Taking Bessel's value for the semiaxis major and the eccentricity of the 

 earth, andh=l7'5 feet as given by measurement and the known height of 

 our standard barometer, the logarithm of the factor for this correction is 

 7-7467623. 



Result. 



Adopting the values for the reduction to a vacuum as found in Table IV., 

 and applying the correction to those experiments, which were made in a 

 highly rarefied medium, we find the following numbers of vibrations made 

 by each pendulum in both positions in a mean solar day in vacuo, viz. for 



