COMPARISON OF ARCTIC AND ANTARCTIC DISTURBANCES. 



269 



already given; the maximum appears about half an hour later than d-ru hrre. PI is said to vary from 

 373y at Matotchkin Schar to less than 5y at Batavia. It is given as 35'8y at Kew, a value similar 

 to that assigned to the other non-polar European stations. 



Commenting on the fact that the value of PI at Christchurch, 12y, is larger than the values at Honolulu, 

 Zi-ka-wei, and Batavia, BIKKK.I.AXD says, p. 108, " This may be explained by the fact that the perturbation 

 in the Arctic regions is often accompaiiii'd by simultaneous perturbations in the Antarctic regions, and 

 it is the effect of these latter thai is noticed in Christchurch. Our material does not, however, allow of 

 certain conclusions being drawn in this matter." 



As BlRKKLAND does not seem to have had any records from south of Christchurch, the above is 

 presumably pure surmise. 



At Kew the short commencing movement was represented by a fall of 5-y in H between times which 

 I make 21h. 8m. and 21h. 16m., and by a bay lasting from 21h. 8m. to 21h. 35m. in the D curve, the 

 element falling l' - 9 and rising !'(). 



The principal disturbance at Kew was represented in H by a rise of 29y from 23h. 4m. to 23h. 19m., 

 a fall of 41y from 23h. 19m. on the 10th to Oh. 16m. on the llth, and a rise of 13y from Oh. 16m. to 

 Oh. 45m. In the D curve there was a bay from about 23h. Om. on the 10th to Oh. 40m. on the llth, the 

 element being depressed. The maximum depression occurred about 23h. 40m. and amounted to 5' 2. 



In the Antarctic, after being comparatively undisturbed for over 12 hours, the traces became distinctly 

 disturbed about 18h. 36m. on the 10th, or 2| hours before the commencing disturbance noted by 

 BIRKELAND, and the disturbance continued without appreciable intermission until 23h. Om., when the 

 lamp went out. When registration was resumed at Oh. Urn. on the llth the disturbance appeared much 

 reduced. The period for which trace is lacking includes unfortunately the major part of BIRKEI.AND'S 

 principal storm. 



The commencing movement in the Antarctic was a rapid fall of 72y in H between 18h. 36m. and 

 1 8h. 53m. The most striking movement, however, prior to Plate XVIII, was an oscillation which appeared 

 simultaneously in D, H, and V. The turning-point, a maximum, occurred at about 19h. 46m. In the 

 course of about 14 minutes D rose 70' and fell 54', H rose and fell 39y, while V rose 25y and fell 33y. 

 There is, however, no distinct movement at this time in the Kew curves. 



During the time covered by Plate XVIII the largest Antarctic movements were as follows, + denoting 

 a rise and - a fall in the element : 



The H trace was off the sheet on the negative side for a few minutes after 21h. 6m., and got off on the 

 positive side at 2h. 28m., remaining off for over 4J hours. 



After the new sheet was put on at Oh. llm. on the llth, the D and V traces appeared no more disturbed 

 than usual. 



Owing to the lack of trace our information is mainly confined to the fact that the disturbances near the 

 commencement of Plate XVIII, which BIRKELAND ascribes to equatorial perturbations, were synchronous 

 with large oscillations in the Antarctic, which formed part of a series which commenced about 18h. 36m., 

 and which persisted without intermission until at least 23h. Om. 



27. February 15, 1903 (hours 13-20, Plate XIX). 



This is classified as a "compound" storm on the following grounds, p. 174, ... "It must thus be 

 assumed that these are in the main polar perturbations ; but the conditions are not simple, indicating, as 



