ygo H1KKKI.AND. THF. NORWEGIAN AURORA 1'OLARIS EXPEDITION, 1 902 1903. 



I'"roni this it will not be difficult to understand how a number of scientists, such as AIRY, WILD 

 and others, have thought they could demonstrate a difference in time between the deflections in earth- 

 current and magnetism, the former being in advance of the latter. It is at any rate by no means im- 

 possible that without their knowing it their conclusions have really been based upon induction-phenomena 

 similar to those here Ipointed out. If we measure the difference in time between various maxima in 

 /> and X S curves of the same set -- for instance, of April 3031, 1894 -- we find for the most 

 part time-differences that vary between about 5 minutes and 20 minutes, or an average of about 

 12 minutes, and thus of an order of magnitude just such as the above-mentioned scientists have found. 



It mav perhaps be unnecessary to point to special cases of induction-phenomena, as the curves 

 exhibit such a multiplicity of them ; but 1 may mention a few of the simplest and most distinct. 



Here too, we find that the direction of the current is what we should expect to find it according 

 to the general law of induction. Such examples can be multiplied considerably. These same con- 

 ditions are, however, not found in all perturbations. For instance, in the storm of the 28th January, 

 1893, o 3'', the I) and N -S curves appear to keep more or less together, while the change in the 

 earth-current curves, which is here very nearly simultaneous, occurs at about the time of the maximum 

 in the //-curve. 



The induction-phenomenon is therefore here seen by comparing the earth-currents with the //-curve. 



In the preceding article we pointed out that from our calculated fields of perturbation for the polar 

 storms, we should sometimes expect to find such a condition, but that it must only be regarded as 

 exceptional. 



Unfortunately we have no time-marks on the earth-current curves, so the time cannot be deter- 

 mined so accurately as in the later perturbations; but \)\ the aid of the short interruptions in the curve 

 we have determined it as accurately as possible, and it seems to show that the conditions here indi- 

 cated an exceptional case of this kind. No certain opinion can be expressed until more is known of 

 the details of the field of perturbation. Something similar may possibly assert itself, for instance in the 

 storms of the 6th March and 8th November, 1893, where the change in the N S curve does not occur 

 so exactly simultaneously with the maximum of the deflection in I). 



\Ve thus find here too the same chief peculiarities in the earth-current conditions as in Germany 

 conditions that agree exactly with those which, according to our theory, we should expect to find. 



It is only in certain unimportant details that the conditions in Germany and France differ from 

 one another. 



1 lere too, we have endeavoured to determine the extent of the magnetic effect of the earth- 

 currents; but the conditions are more difficult to deal with from the fact that the earth-currents may 

 How under different azimuths. 



