216 OBSERVATIONS OF THE MAGNETIC FORCE IN IRELAND. 



Consequently, 



tan w = - '6661, w = - 33 40', t = -0001047.* 



The lines of total intensity thus deduced are laid down in the 

 annexed chart for differences of '005, these differences correspond- 

 ing to intervals of 47'6 geographical miles. It will be seen that 

 their direction diverges widely from that of the lines of dip ; 

 and although the position of the two classes of lines may need 

 further correction, it does not seem likely that such correction will 

 have the effect of diminishing, at least by any considerable amount, 

 the divergence. 



* The mean inclination of the isodynamic lines deduced with the help of additional 

 observations is u = - 35 0', the rate of increase in the perpendicular direction remain- 

 ing unaltered. Eighth Rpeort of the British Association for the Advancement of Science, 

 p. 185. 



