2G2 COMPARISON OF ARCTIC AND ANTARCTIC DISTURBANCES. 



The movements just recorded extend over BIRKELAND'S Sections (i) and (ii) and show no interlude. 



Until 21h. the H trace was mostly off the sheet on the negative side, appearing at intervals for a few 

 minutes at a time. The most striking movement seen during this time answered to a peak at about 

 19h. 19m. The trace was visible for about 8 minutes, during which H rose and fell 687. This happened 

 synchronously with an exceedingly rapid oscillation in D, that element in the course of 11 minutes falling 

 97' and rising 88'. 



Later the H trace was more in evidence. Between 20h. 53m. and 21h. 8m. H rose 66y and fell 49y 

 with minor oscillations. Between 21h. 8m. and 21h. 20m. it rose 140y, the trace then going off the sheet 

 on the positive side and remaining off for 20 minutes. 



On reappearing at 21h. 40m. the H trace fell 136y in 7 minutes, then rose 54y and fell 70y in the course 

 of the next 11 minutes, and went off the sheet on the negative side about 21h. 58m. It was not again 

 seen, except for a few minutes, until about 22h. 37m., when it appeared and rose 103y during the next 

 10 minutes. 



There were numerous minor oscillations all this time in the V trace, the most striking being a fall of 65y 

 and rise of 50y between 19h. 17m. and 19h. 28m., a time during which there were also rapid oscillations in 

 D and H. But perhaps the most outstanding feature is the continuous downward tendency of the curve 

 from 16h. 15m. to 21h. 40m., the total fall during this time being about 300y. After some small oscillations 

 V then commenced to rise rapidly, the rise between 21h. 57m. and 22h. 42m. representing 182y. 



From 23h. 13m. on the 23rd to Oh. 19m. on the 24th there was no paper on the drum, and though 

 substantial alterations took place in the values of the elements during this interval it may have been 

 quieter than the times before or after. But there is no direct evidence of any marked lull from the 

 commencement, about 15h. 20m. on the 23rd, until lOh. on the 24th. No subdivision into sections nor 

 difference in source is at all suggested by the Antarctic D and II curves. 



The case of V is rather different, as that element, on the whole, rose between 15h. 35m. and iGh. 15m., 

 and again between 21h. 40m. and 22h. 42m., while it fell during the intervening time. 



In the Antarctic there can be no question that the disturbance of October 31 to November 1 was smaller 

 than that of November 23-24. The range of the elements appears greater at Kew on the former occasion, 

 but that is due to the fact that the period was longer and included the ordinary hours of the daily 

 maximum and minimum. The appearance of the Kew curves would indicate that the later disturbance 

 was the more intense, and this is really borne out by BIUKELAND'S figures on pp. 240 and 280 for the 

 amplitude of the disturbing force. 



18. December 9, 1902 (hours 5-18, Plate IX). 



This is entered amongst the " equatorial " storms. When discussing it on p. 70 BIRKELAND describes 

 the disturbance as illustrating at its commencement " all the properties that characterise the positive 

 equatorial perturbations. It commences quite suddenly, simultaneously all over the Earth, at 5h. 40' 6m." 

 This movement is seen in the Arctic as well as the non-polar regions. It is, however, by no means large 

 at most stations. At Kew, for instance, the initial rise in H was only about 5y and it was not very rapid. 

 BIRKELAND regards "equatorial" conditions as persisting until nearly 15h. During this time there are no 

 large movements even in the Arctic. 



" Between 15h. and 18h., the character of the perturbation conditions is essentially changed. It is this 

 feature that we continually find repeated, namely, that when the equatorial storm has lasted for some hours, 

 polar systems appear." p. 70. During the time stated there was a disturbance of some size at all the 

 Arctic stations, and even at the non-polar stations there were appreciable bays on both the H and D curve*. 

 Thus at Kew the H trace shows a bay from ICh. 25m. to 17h. 40m., the greatest depression representing 

 about 15y; corresponding to this was a hump on the D curve, the maximum representing a rise of 

 about 2' - 5. 



In the Antarctic there were of course numerous movements larger than any at Kew, but there is no 

 very decided trace of disturbance until towards the end of the period covered by Plate IX. On this 

 occasion it is very doubtful whether there is anything in the Antarctic curves corresponding to the sudden 

 movement seen elsewhere about 5h. 41m. There is, it is true, apparently at this exact time a trifling but 

 sharp peak in the V trace which previously was very quiet representing a very rapid rise and fall of 



