trend of arches appears to be the most definite. The constant N.W.-S.E. trend at 

 Cape Adare is associated with the passage overhead of the " auroral spiral." That 

 portion of the spiral which passes above Cape Evans is, however, much less constant 

 in direction (N.-S.), and there is a suspicion, at least, of a change in direction (anti- 

 clockwise rotation) with time. This part of the spiral is therefore closer to the centre 

 where the spiral is more strongly curved and possibly more variable in curvature on 

 successive days. 



The fact that the spiral lies overhead both stations at about the same time in the 

 morning gives (not very convincing) information as to the form of the auroral spiral 

 in these latitudes. 



A natural consequence of this theory is that, for stations in equal magnetic 

 latitudes,* the aurora should pass overhead at the same magnetic local time, where the 

 magnetic local time bears the same relation to the magnetic axis, as does local time 

 to the rotation axis of the earth. 



The results of observations in the northern auroral zone are similar to those 

 described above in that two maxima, one in the evening and one in the morning, are 

 found, with a more or less pronounced minimum between. The strongly coloured, 

 quickly moving and brilliant auroraa are more frequent in the afternoon than in the 

 morning, while the reverse is true for faint aurorge.f We have, therefore, considerable 

 support for suggesting that the secondary (afternoon) maximum is of quite a different 

 type to the morning maximum and is probably connected with brilliant aurorse and 

 possibly (as will be seen later) with magnetic disturbances. Thus, the morning 

 maximum seems to be a frequency maximum, and the afternoon maximum an intensity 

 maximum. 



In the foregoing, the occurrences of " clear, no aurora," have not been considered, 

 but an examination of the diurnal variation is not without interest. As the chief 

 auroral maximum occurs at both stations in the morning, we should naturally expect 

 the fewest occurrences of " clear, no aurora," at this time, with the maximum 

 frequency at the time of minimum auroral frequency in the afternoon. This is indeed 

 the case at the Cape Adare station, though only the morning minimum is well marked. 

 At Cape Evans also, a minimum occurs in the morning at 4 to 5 hours, with a maximum 

 in the evening at 22 hours, though neither are well denned. 



It is of great interest to note that the relative number of observations of aurora 

 and of "no aurora" at Cape Evans in the years 1911 and 1912 were the same, 

 notwithstanding the fact that the number of sunspots observed in 1912 was 

 considerably less than in 1911. This argues that the presence or absence of aurorae 

 viewed from the Cape Evans station may be nearly independent of the sunspot 

 frequency. This is reasonable on the view that, apart from the intensity maximum 

 in the afternoon, the presence or absence of aurora is largely independent of spots ou 



* The magnetic latitude bear* (lie same relation to the earth's nm^m-tn- axis as iluc.s tin- astronomical 

 latitude to the earth's rotation axis. 

 f L. Vegard, loc. cit. 



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