260 



COMPARISON OF ARCTIC AND ANTARCTIC DISTURBANCES. 



We may regard the V movements during this time as composed of four " waves," whose times and 

 amplitudes were as follows ( + denotes a rise, - a fall) : 



Each " wave " except the third left V enhanced, so that the final value exceeded the original by 60y. 

 There were four " waves " in D roughly corresponding to those in V. 



During the first D fell 75' and rose 72'. 



second 102' 133'. 



third 81' 195'. 



fourth 173' 80'. 



H fell 108y between 9h. 32m. and lOh. 23m., rose 56y between lOh. 23m. and llh. 5m., and fell 57y 

 between llh. 5m. and llh. 30m. The trace went off the sheet on the negative side at llh. 30m., 

 remaining off until 12h. 46m. It came on again, but only for a few minutes, showing a double peak at 

 12h. 50m., and was thereafter no more seen until 20h. 53m. 



The last of the four waves above mentioned in the Antarctic synchronises with BIRKELAND'S first 

 " intermediate " polar storm. But it seems impossible to draw any line of demarcation, such as BIRKELAND 

 draws, between it and what precedes. The four waves are of the same type and follow in immediate 

 sequence, and it is difficult to believe that the first three can be due to " equatorial " perturbation if the 

 last is due to " polar." The storm in the Antarctic probably existed for some hours before 8h. 51m., as 

 the D trace contains two bays similar to, though smaller than, the four we have described. The H trace, 

 however, was off the sheet after Ih. 20m., and the V magnetograph not working until nearly 8h. 51m., so 

 our information is very limited before this hour. 



After 14h. 1m. there was probably an absence of large rapid movements in the Antarctic until nearly 

 21h. The H trace was off the sheet, and the D trace also after 17h. 40m., but the V trace remained on 

 until the sheet was taken off at 22h. 7m., and its course was unbroken by any oscillations at all comparable 

 with the four we have described. There was, however, a persistent fall in V, as if the cumulative effect 

 of the four waves were gradually disappearing. The total fall between 14h. 1m. and 20h. 41m. amounted 

 to fully 70y. 



After 20h. 50m. there were some more wave-like movements in the V trace, though not so large as the 

 earlier ones. The two principal consisted, the first of a fall of 21y and rise of 12y between 20h. 50m. and 

 21h. 28m., the second of a fall of 30y and rise of 16y between 21h. 28m. and 22h. 9m. 



' The H trace, after having been beyond the limits of registration on the negative side for nearly 8 hours, 

 came on the sheet at 20h. 58m., and H rose 89y between that hour and 21h. 30m. Rising further, with 

 minor oscillations, it got off the sheet on the positive side at 22h. 2m., having risen HOy since 20h. 58m. 



There was no record from 22h. 7m. to 23h. 46m., which covers half the time of BIRKELAND'S second 

 "intermediate" storm. When the next sheet was put on at 23h. 46m., the H trace was off the sheet on 

 the positive side, and it remained off until 4h. 30m. on November 1. The D and V traces on the second 

 sheet show, however, no signs of special disturbance. The largest movements in the V trace are two bays, 

 the first, from Ih. 33m. to 2h. 45m., having a rise and fall of only 16y, the second, from 2h. 45m. to 

 3h. 56m., showing a rise of 43y and fall of 27y. 



