266 Observations 07i ihc Direction and Intensify of the [Ai nii. 



To deduce from these values of the times occupied by each cylinder 

 to perform 100 vibrations, the relative horizontal magnetic intensities 

 the several places : let T represent the time of any needle perfarmins; 

 100 horizontal vibrations at Madras ; and T', the time occnpied by the 

 same needle, to perform 100 vibrations at any other place, and let //, and 

 h' represent the horizontal intensities at those places : then we get 



h' \ T t 



Applying this formula to the Madras and Trivajidrum observations, 

 and putting h = \ we have 



T.G.T. 1. T.G.T. 2. T.G.T. 3. J. C. 1. J. C. 2. 



Madras 273,98 29 J, 41 2(36,08 201,97 277,04 



T«iv.vn«T-M / 20431 204,47 277,91 



lRi\ANDRLM.... I .^^^ yg ^^3 -^^ 269,07 204,07 278,78 



h' = ... 0,098032 0,982860 0,977899 O,97760S 0,994905 



Mean value of A' = ,98(326 



Assuming A' as ju't found, if we now compare the observations made 

 between Vadinatrum and Tellichernj with those made at Trivandrum ; 

 and (recollecting that A = 1,) compare the observations at the remain- 

 ing stations with those mude at Madras, we get altogether as follows : — 



