PART I. ON MAGNETIC STORMS. CHAP. II. 



6 7 



TABLE XI (continued). 



Only small oscillations about the normal line, without 

 any distinct deflection. 



Dyrafjord. 



The declination-curve not drawn here. The horizontal 

 intensity oscillates about the normal line. 



For Wilhelmshaven and Pola P, directed upwards, for Christchurch directed downwards. In all 

 cases too small to allow of being measured. 



Figures 30 and 31 give the position of the current-arrows corresponding to the perturbation on 

 the 26th January, 1903. The current-arrows are constructed in the manner explained in Art. 23, by 

 the aid of the values for PI,, Pd and P, given in Table XI. 



With regard to the times employed, it should be said that the first is chosen immediately after the 

 commencement of the perturbation, and thus represents the magnitude of the perturbing forces that at 

 that hour suddenly make their appearance upon the earth. After this hour the oscillations diminish 

 somewhat - as Table XI and Plate XIV show -- until at about n h 2o m in many places they have 

 already become 0. Between g h and I2 h , the conditions at the various stations are on the whole only 

 slightly changed, and remain fairly constant, with small perturbing forces. For this intermediate period 

 therefore, no charts have been constructed. After I2 h , however, the oscillations begin to increase, attain 

 their highest value a little before 14'', and then rapidly decrease to zero. These conditions will be found 

 represented on the last three charts. On Chart IV the length of the arrows in certain tracts is a little 

 abnormal, as the way in which the force increases towards the equator is not very clearly distinguishable. 

 This is partly accounted for by the fact that the force at this time varies so greatly, that a slight dis- 

 placement in time may cause considerable changes. Even the small polar precipitations, moreover, will 

 exert an influence. They will possibly assert themselves most in North America - Toronto and Sitka 

 (cf. the perturbation of the I5th Dec., 1882; chap. III). 



