130 



BIRKEI.AND. THE NORWEGIAN AURORA POLARIS EXPEDITION, 19021903. 



THE PERTURBING FORCES. 



47. The total of the perturbing forces is calculated for a number of hours, and marked upon charts. 

 As the polar perturbation is so much greater than the equatorial, the field of force shown, per- 

 haps with the exception of the equatorial regions, is mainly conditioned by the polar system. 



TABLE XIX. 



TABLE XX. 

 The Perturbing Forces on the 22nd March, 1903. 



I 1 ) The value of Pi,, there being no declination curve. 

 ( 2 / The normal line somewhat uncertain. 



