272 COMPARISON OF ARCTIC AND ANTARCTIC DISTURBANCES. 



disturbing forces much larger than those shown by tho curves in equatorial and temperate latitudes is a 

 fact which requires a good deal of explanation on the hypothesis of //;nA/;-/rt/ electric currents. 



From 15h. 5m. to 18h. 15m. the Antarctic curves, like those elsewhere, were, on the whole, distinctly 

 quiet. From 18h. 15m. to 18h. 25m. there was a more prominent oscillation in II, a fall of 14y being 

 followed by a rise of 16y, while V rose 16y between 18h. 22m. and 18h. 26m. 



Between 19h. 13m. and 19h. 22m. H fell 20y and rose 24y, while between 19h. 32m. and 19h. 35m. it 

 rose 16y and fell 17y, the latter an exceptionally rapid though not large oscillation. 



After 20h. 15m. conditions became more disturbed in all the elements. The oscillations, though not 

 really large, were unusually rapid between 20h. 15m. and 22h. 15m. 



The D and H traces got rather mixed up and are difficult to distinguish. Amongst the movements in 

 the V trace after 20h. were 



a fall of IGy between 20h. 14m. and 20h. 19m., 



a rise of 24y 20k. 19m. 20h. 24m., 



and a fall of 39y 20h. 24m. 20h. 31m. 



After this there were numerous small but rapid oscillations, during whose incidence V rose to a maximum 

 at about 21h. 13m. There then ensued a fall, interrupted by minor oscillations, which continued until about 

 22h. 40m., in the course of which V fell 56y. This was followed by a rise of 97y in two steps between 

 22h. 40m. and 23h. 25m., the rise being conspicuously most rapid during the first 20 minutes. From 22h. 20m. 

 to 23h. 3m., simultaneously with the most rapid part of the change in V, there was a prominent bay on 

 the H curve, the element falling 61y and rising 36y. 



After 23h. the D and H traces were somewhat uncertain owing to operations connected with the 

 clearing away of snow near the Magnet Hut, and the record was suspended altogether from 23h. 37m. to 

 Ih. 5m. on the 23rd. 



It will have been noticed that the large rise in V and the prominent bay on the H curve took place 

 during BlRKELAND's " elementary polar " storm. 



So far as mere amplitude is concerned, the large rise in V after 22h. 40m. is, perhaps, the only 

 phenomenon which merits the title of disturbance as judged by the Antarctic standard. The number, 

 however, of minor oscillations in V and the rapidity of the oscillations in D and H, especially H, are 

 certainly a little outstanding. 



29. March 30-31, 1903 (hours 19-3, Plate XXI). 



This is classed amongst the "elementary polar" storms. BiRKELAND explains, however, pp. 115-117, 

 that this "elementary" storm was preceded by an "equatorial" perturbation. He adds, p. 116: "As 

 early as 19h., those little, sudden, very variable perturbations are noticed, which occur simultaneously all 

 over the Earth. . . The ("equatorial") perturbation appears to be over at about 23h. 12m. . . ." 



The " polar " perturbation is said to be recognisable at Kaaf jord about 23h., being earlier there than 

 elsewhere. It did not commence at Dyrafjord until about Oh. 24m. At non-polar stations the commence- 

 ment was, in general, about 23h. 50m., the end about 2h. 10m. on the 31st. The hour of occurrence of 

 the maximum is given as Oh. 30m. for temperate Europe, but Oh. 58m. for Dyrafjord. The maximum 

 value of the horizontal component of the disturbing force varied from 546y at Dyrafjord to 10 -5y at 

 Batavia. The value for Kew, 41 - 5y, is about a mean for non- Arctic Europe. 



The earliest decided movement shown in Plate XXI at non-Arctic stations is a small oscillation 

 apparent in almost all the H traces and in some of the D traces. At Kew the double movement lasts 

 from about 19h. 23m. to 19h. 31m., the turning-point coming about 19h. 27m. There was a rise of 7y 

 and then a fall of 6y in H, while D fell and then rose 1' 3. 



While examining the original Kew curves I noticed a somewhat conspicuous movement of similar size 

 and character about an hour and fifty minutes earlier. This consisted in the case of H of a rise of 6y 

 between 17h. 32m. and 17h. 36m., followed by a fall of 9y between 17h. 36m. and 17h. 40m. The reason 

 for mentioning this will appear presently. 



During the whole time covered by Plate XXI the most conspicuous phenomenon at Kew (and the same 

 is true generally of the other non-polar stations) took place between Oh. 10m. and Ih. 10m. of the 31st, 

 i.e. during the "elementary polar" storm. D, which had fallen l'-8 between 23h. 45m. and Oh. 10m. on 



