ON THE ELLIPTICITY OF THE EARTH. 



469 



several stations computed by and corresponding to these 

 values of the equatorial rate of vibration, and of the 

 increase of gravity from the equator to the pole ; 

 together with the vibrations actually observed at each 

 station, and the differences, or what may be properly 

 termed the discrepancies, of the observed vibrations : 





From the column of " differences " we may obtain 

 the " probable error " of the vibrations at a single sta- 

 tion, and the proportion in which the probable error is 

 diminished as the number of stations is increased. Of 

 a single station the probable error is l s *7 ; of 10 stations, 

 O s< 55.; and of 22 stations (the number in the table), 



