6 4 



RIKKF.LAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, 19021903. 



TABLE X. 



The above question, which is of great importance, cannot be definitely decided until we are in 

 possession of rapid registerings, as usual of 12 times the rapidity of the daily registerings. By this means 

 we should see if the apparent difference in time, as shown in Table X, between, for instance, Honolulu 

 and Batavia, is a real one. 



The perturbing force is calculated for a number of hours, the results being given in the annexed 

 Table. It should be remarked that as the perturbation is of rather long duration, the perturbing force 

 will be somewhat uncertain for the middle part of the perturbation. It will be seen from the Table 

 that the horizontal component of the perturbing force is directed, as already mentioned, along the mag- 

 netic meridian, except as regards the most northerly situated stations. Further, the force decreases 

 somewhat in strength from the equator to the poles, as the charts very distinctly show. 



If we compare the force on the two sides of the equator, we see that the course is similar, but 

 that the force has a smaller value at Honolulu than at Dehra Dun, Bombay and Batavia. 



The curve for the magnetic equator, or rather the line of intersection of the plane perpendicular 

 to the magnetic axis, with the earth, is also drawn on the charts. We see that the direction of the 

 arrows is on the whole parallel with this line. 



As compared with the horizontal component, the vertical component of the perturbing force is 

 exceedingly small; and this proportion continues as far as Pawlowsk, as far, indeed, as the Norwegian 

 stations about the auroral zone. There is, however, in the south, namely, at Christchurch, an un- 

 doubted deflection in the vertical-intensity curve, answering to a force-component directed downwards, and 



(') The curves for Baldwin, Toronto and Cheltenham are so finely serrated as to make identification difficult 



