270 COMPARISON OF ARCTIC AND ANTARCTIC DISTURBANCES. 



they do, both in the Arctic regions and in lower latitudes, that there are a number of systems acting to 

 some extent simultaneously." 



According to BIRKELAND, one noteworthy peculiarity is that the disturbance at most stations commenced 

 nearly '2 hours later, while ending nearly half an hour earlier in 1) than in H. 



In Europe, outside the Arctic, the H disturbance is given as lasting from about 14h. 15m. to 18h. 15m., 

 and the D disturbance as lasting from about 16h. 10m. to 17h. 45m. The time of the maximum 

 disturbance is given at most stations as near 16h. 40m. The maximum value of the disturbing force 

 in the horizontal plane varied, according to BIRKELAND, from 392y at Axelden to 10 -67 at Honolulu, the 

 value at Kew, 38y, being similar to that at most non-polar European stations. 



There were no Christchurch results. 



In Europe generally, outside the Arctic, the disturbance consisted of a slight depression in H from about 

 14h. 15m. to 18h. 15m. the maximum depression at Kew below the normal being about 20y and 

 occurring about 16h. 30m. and of a more conspicuous, depression in D. At Kew there was a fall of 6' - 5 

 in D between 16h. 10m. and 16h. 45m., followed by a rise of 4' '8 between 16h. 45m. and 17h. 20m. 

 After a stoppage of nearly 20 minutes there was a further rise of about 2' going on until nearly 18h. 30m. 

 This final rise, however, is so slow that opinions might well differ as to its duration and significance. 



In the Antarctic the curves would hardly be described as disturbed before 16h. Between 13h. 41m. 

 and 14h. 53m., however, D rose 66', while H fell 64y between 13h. 17m. and 14h. 53m. There were two 

 successive bays on the D curve, the first from 16h. 3m. to 17h. 10m. with a rise of 51' and fall of 31', the 

 second from 17h. 10m. to 18h. 10m. with a fall of 52' and rise of 57'.' The H trace, which had been off 

 the sheet on the negative side for about 45 minutes, came on the sheet at 17h. 23m., and H rose 63y by 

 17h. 50m. Following this were a number of oscillations of some size, H rising on the whole until 

 19h. 33m., the total rise since the trace came on the sheet at 17h. 23m. being about 105y. During this 

 time the V trace shows two fairly prominent bays, the first lasting from 15h. 53m. to 17h. 5m., the second 

 from 17h. 5m. to 18h. 13m. The first bay represents a rise and fall of about 25y, the second a rise and 

 fall of about 48y. 



Up to 18h. 40m. there were no very rapid movements. Between 18h. 40m. and 18h. 55m., however, 

 there were simultaneous rapid oscillations in D and H ; D rose 52' and fell 48', while H fell 62y and rose 

 75y. During part of this time, from 18h. 43m. to 18h. 48m., there was a smart rise of 25y in V. This 

 was followed by a larger but slower fall of 32y from 18h. 48m. to 19h. 3m. 



Conspicuous movements in D and H were just concluding at 20h. Om., the hour answering to the end 

 of Plate XIX. D had risen 42' in the course of the previous 11 minutes, whilst H had fallen 64y since 

 19h. 46m. These movements seem, however, to be related rather to what follows than to what precedes 

 them. For after a small retrograde movement H continued to fall to a very sharp peak at 20h. 3m., the 

 total fall since 19h. 46m. amounting to Sly. The peak at 20h. 3m. answers to a depression (minimum) in 

 V, rather suggesting that the preceding fall answered to the first phase of a disturbance of the " special 

 type." If this view is correct, the second phase is represented by a rise of 78y in H and of 23y in V, 

 which took place between 20h. 3m. and 20h. 16m. This was immediately followed, between 20h. 16m. 

 and 20h. 38m., by another double movement, also suggestive of the "special type" of disturbance. The 

 H change in this second oscillation was a fall of 72y and rise of 56y, the V change a fall of 36y and rise 

 of 43y. This movement was followed by yet a third sharp oscillation in H and V, terminating about 

 20h. 54m. The range of H, however, in the third oscillation was only 32y, the fall and rise being equal, 

 while the V movements were under 20y. During these three oscillations there were also oscillatory 

 movements of some size in D, the total range in D between 20h. 3m. and 20h. 54m. amounting to 50'. 

 The oscillations in D were, however, much interrupted by minor oscillations, and it is difficult to decide on 

 their exact relationship to the H and V movements. 



One would put the commencement of the quiet time in the Antarctic at the end of the third oscillation, 

 i.e. at 20h. 54m., and one would unquestionably regard the disturbances from 19h. 46m. to 20h. 54m. 

 as forming part of a common system. 



28. March 22-23, 1903 (hours 12-1, Plate XX). 



This is classed amongst the "elementary polar" storms, but BIRKELAND, p. 127, explains that "The 



