24G 



COMPARISON OF ARCTIC AND ANTARCTIC DISTURBANCES. 



APPENDIX B. 



An Examination of Antarctic disturbances from October, 1902, to March, 1903, which are simultaneous 

 with Arctic disturbances discussed by Prof. KR. BIRKELAND. 



1. AFTER the discussion of the Antarctic magnetic data on pages 73 to 200 had been completed, there 

 appeared a large volume by Prof. KR. BIRKELAXD* which contains a great mass of information respecting 

 magnetic disturbances in the Arctic, from October, 1902, to March, 1903, which were contemporaneous 

 with the observations discussed in this volume. 



Prof. BIRKELAND had the following four Arctic stations, all provided with self-recording 

 magnetographs : 



Guided by the records from these stations and from Potsdam, Prof. BIRKELAND made a list of 

 disturbances and issued a circular to magnetic observatories requesting copies of the records obtained 

 on the days specified on his list. He thus became possessed of records of disturbances at 25 stations, 

 including the four mentioned above and the following : 



In Europe Bossekop, Pawlowsk, Stonyhurst, Wilhelmshaven, Potsdam, Kew, Val Joyeux, Munich, 

 Pola, San Fernando ; in Asia Tiflis, Zi-ka-wei, Dehra Dun, Bombay, Batavia ; in N. America Sitka, 

 Toronto, Baldwin, Cheltenham ; in the Pacific Honolulu and Christchurch. The names in each group 

 are in order of latitude from north to south. 



BIRKELAND reproduces the disturbed curves in 21 plates, each dealing with a disturbed period varying 

 in length from 2 to 20 hours. Some of the observatories supplied no Vertical-Force curves, and only a 

 few supplied material for all the magnetic storms. Still, the plates represent what is probably the most 

 extensive series of contemporaneous magnetic data that has yet been published. In addition to the plates, 

 the volume contains over 160 charts representing the results which BIRKELAND has deduced for the 

 disturbing forces at the different stations, at different stages of the 21 storm periods. These charts 

 are based on elaborate measurements of the magnetic curves and represent a large amount of work. 

 Besides discussing the charts, BIRKELAND deals with experiments which he has made with a miniature 

 Earth, or terrella, magnetised and exposed to kathode-ray discharges in a high vacuum. The experiments 

 are intended to serve as an auxiliary to the elucidation of the causes that produce magnetic disturbances. 

 The discussion of observations, experiments and theory occupies more than 300 large quarto pages. 



2. As already mentioned, the discussion originally contemplated of Antarctic niiignetic storms had been 

 entirely completed when Prof. BIRKELAND'S volume came into my hands in February, 1909, and I was 

 exceedingly reluctant to re-open the subject, considering the long time that had already elapsed since the 

 work was begun. It was accordingly decided that no change should be made in what had been already 

 written, and pages 73 to 200 are thus absolutely unaffected by any results or views in BIRKELAND'S! 

 volume. When Prof. BIRKELAND'S conclusions and mine harmonize, the harmony thus merits increased 

 consideration ; when they differ, the difference at least owes nothing to prejudice. 



* 'The Norwegian Aurora Polaris Expedition, 1902-1903,' Volume I. 



t The reference in Chapter IX is to Prof. BIBKELAND'S earlier work, ' Expedition Norvegienne de 1899-1900.' 



