COMPARISON OF ARCTIC AND ANTARCTIC DISTUKIUXCKS. 255 



12. October 23-24, 1902 (hours 17-5, Plate III). 



This is described, p. 76, as "a positive equatorial perturbation. It commences suddenly at 19h. lira., 

 simultaneously all over the Earth." It is added, however, "About 1 hours later, a polar storm. . . 

 characteristic, simple, and well defined, appears around the Norwegian (i.e. Arctic) stations . . . especially 

 distinct at Matotchkin Schar." The date was riot in BiRKELAND'.s list, so he obtained curves from only a 

 few stations, including, however, Bombay and Dehra Dun. 



The sudden commencement is shown clearly at all the stations, including the Arctic ones. At Toronto, 

 and at Axeloen in the D curve, the commencing movement appears distinctly double, the principal move- 

 ment being preceded by a smaller movement in the opposite direction. At Kew there is only a suggestion 

 of an initial fall in H, but nothing certain prior to a sudden rise, amounting to 17y in the course of 3 or 

 4 minutes. After the summit was reached at 19h. 14m., there was a gradual return to an undisturbed 

 value at about 19h. 35m. Simultaneously with the change in H there was a very small change in D, 

 westerly Declination rising and falling about 0' 7. 



In the Antarctic the curves had been unusually quiet for some hours when there suddenly began, at 

 19h. 10m., an exceedingly rapid rise in H. The movement is too rapid to be distinctly shown, but the 

 trace seems to have gone off the sheet, remained off for 2 minutes, and returned to near its original 

 position in 5 or 6 minutes. How much the oscillation exceeded that shown, + 40y, then - 35y, it is of 

 course impossible to say. After slackening for a minute or two about 19h. 16m., H continued moving in 

 the same direction as before, to a peak at about 19h. 22m. The fall in H since the curve came on the 

 sheet was 77y. Simultaneously with the commencing movement in H there was an oscillation in D, a fall 

 and rise each of 15' taking place in about 4 minutes ; this was followed by a second smaller oscillation. 



The V trace, which had been exceedingly quiet, showed also a marked commencing movement, consist- 

 ing of a rise of 67 in 3 or 4 minutes to a sharp peak at about 19h. 14m., followed by a fall of 26y, occupying 

 about 8 minutes. Halfway during the fall there was a nearly stationary position during about 2 minutes. 



The natural conclusion unquestionably is that these large sudden movements in the Antarctic correspond 

 to the smaller commencing movements which appeared simultaneously elsewhere. 



The principal disturbance in the Arctic occurs between 21h. and 23h., the maximum coming about 

 22h. 20m., but the Axeloen curves appear considerably disturbed until 3 a.m. on the 24th. The non- 

 polar curves in Plate III show only very trifling disturbances, the largest, between 21h. and 23h. on the 

 23rd, being only of the same order as the sudden commencement at 19h. llm. 



In the Antarctic the conditions remained highly disturbed from 19h. 10m. until the traces got on the 

 clamp at about 23h. 6m. The D and H traces show incessant large oscillations. The largest movements 

 recorded in H were a rise of 84y between 19h. 56m. and 20h. 13m., and a rise and fall each of 67y 

 between 22h. 51m. and 23h. Om. The curve came on the sheet at 22h. 51m. and went off 9 minutes 

 later. Coming on again immediately, II rose 44y in a few minutes, the trace coming on to the clamp and 

 so being lost. 



In D there was a rise of 94' between 22h. 18m. and 22h. 25m., followed by a fall of 100' during the 

 next 10 minutes. Between 22h. 51m. and 23h., synchronous with the large changes in H, there was a 

 fall of 54' and a rise of 87', the latter immediately followed by a rapid fall of 135', the trace coming on to 

 the clamp before the movement was completed. 



Amongst the larger V movements were a fall of 26y and a rise of 22y between 19h. 54m. and 20h. 26m., 

 a fall of 20y between 22h. 26m. and 22h. 33m., and a rise of 51y between 22h. 33m. and 22h. 53m. 

 Between 22h. 53m. and 23h. 6m.. when the trace got on the clamp, V fell 24y, rose 37y, and fell 27y. 



The larger D and V movements, it will be noticed, occurred during the time when the Arctic 

 stations were most disturbed; but the disturbance in the Antarctic was continuously large between 

 19h. 10m. and 23h. 



The conditions in the Antarctic had become distinctly quieter by Oh. llm. on the 24th, when the next 

 sheet was put on, but might fairly be described as disturbed until 3h. 30m. 



There was a small bay from Oh. 17m. to Oh. 53m., the changes in the three elements being at least 

 approximately simultaneous. D rose 25' and fell 51', just going off the sheet on the positive side; while 

 V rose 16y and fell 13y. The H trace was off the sheet on the positive side for 10 minutes and the rise, 



