(JENERAL DISCUSSION OF AURORAL OBSERVATIONS. 



Before proceeding to a discussion of the correspondence between magnetic 

 disturbances and auroral displays, it is advisable to review the data before us and to 

 see if the conclusions are in agreement with those which have been drawn from 

 observations on the Aurora Borealis. 



Though the aurora was seen much less frequently at Cape Evans than at Cape 

 Adare and was at the former station much less brilliant, there is considerable similarity 

 between the two sets of observations. In both cases, the aurora showed a striking 

 partiality for certain sectors combined with an even stronger tendency to avoid 

 other sectors. At Cape Evans, the maximum is in the E.N.E. and the minimum 

 in the west ; at Cape Adare the maximum is in the north and the minimum 

 in the S.W. ; in each case, the angle between the two, measured through east, is 

 slightly more than 180. 



In each case, the aurora first appears in the " maximum sector," i.e. the sector 

 in which it is most frequently seen, gradually approaching the station, and sometimes 

 passing overhead and disappearing in the direction of the '' minimum sector." At 

 Cape Evans, the aurora passes overhead infrequently, and is seen in the " minimum 

 sector," or sector in which it is least frequently seen, only rarely. The trend of the 

 arches is fairly constant at both stations, but particularly so at Cape Adare, and in 

 both cases the direction of movement is from the "-maximum sector " to the " minimum 

 sector," the direction of movement being also at right angles to the trend of the an-h. 



At both stations, the average time of occurrence in the '' minimum sector " is 

 somewhat later than the average time of occurrence overhead. 



The time at which the aurora passes overhead is, in the case of Cape Evans, at 

 5 hours (time of 180th meridian), and in the case of Cape Adare, at 4 hours (local time). 

 The occurrence in the zenith is, therefore, almost simultaneous at both stations, though 

 these are separated by some 6 degrees of latitude. 



Not unnaturally, the time at which the aurora is most frequently seen overhead 

 is also the time at which aurora is most frequently seen. 



At Cape Adare, a secondary maximum occurs at 20 hours, followed by a minimum 

 at 22 hours, both of which are most clearly marked in aurorse seen close to the zenith, 

 and in bright and coloured aurorse. Traces of a secondary maximum and the following 

 minimum are also seen at Cape Evans, but not so clearly, though the occurrences of 

 brilliant aurora? are more frequent in the afternoon than the morning, a result we 

 have already suggested as indicative of a real difference between the character of the 

 morning and evening maxima. It is interesting also to note that the minimum which 

 immediately follows the Cape Adare maximum is a very sharp one, followed by a 

 sharp recovery at midnight. 



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