VARIATIONS OF THE MAGNETIC NEEDLE. 



279 



TABLE III. 



Calculated Values of the Intensity of the Earth- Currents, in the Line connecting 

 Derby and Rugby. 



8. For the line connecting Derby and Birmingham, we have 



= 4- 33 27', = 4- 55 52' ; 

 and, introducing these values, the formula becomes 



g Y 

 0001C3 fy - 0-83 ~ 



