786 Mr. Charles Chree [March 4, 



monumental work,"Tlie Xorwegian Aurora Polaris Expedition 1902-o, 

 vol. 1." The slide shows part of one of these plates, containing 

 horizontal force curves for March 22, 190;^. On this occasion, a 

 " polar elementary " storm supervened after an " equatorial " storm had 

 been in evidence for 8 hours. In the present instance the " equatorial " 

 storm can be recognised readily from Axeloen (77° 41' N. lat.) to 

 Christchurch (43° 32' S.), the extreme stations for which Birkeland 

 had records, and its magnitude appears of the same order everywhere, 

 whereas the " polar elementary " storm, though visible in most if not 

 all of the stations, is much largest in the Arctic. 



Whilst recognising to the full the devotion with which Prof. 

 Birkeland has prosecuted his investigations into magnetic storms for 

 over a decade of years, and while admiring his gifts of imagination 

 and the beauty of his experiments, I have to admit that I do not find 

 his explanations convincing. If " equatorial " storms are dne, as he 

 believes, to electric currents at great heights above the earth in the 

 magnetic equator, the disturl )ing force, while approximately horizontal 

 and in the magnetic .meridian at places near the magnetic equator, 

 should even in temperate latitudes have a considerable vertical com- 

 ])onent, and near the magnetic poles the vertical component should 

 largely predominate. I am unable to see these phenomena in the 

 curves of Birkeland's own plates, and I have other evidence which 

 seems very unfavoural)le to his views. During the time of Bu'keland's 

 Arctic expedition the ' Discovery ' was at work in the Antarctic, and 

 the simultaneous results obtained there do not seem capable of expla- 

 nation on Birkeland's hypothesis. I would specially draw attention to 

 two oscillatory movements near the commencement of the " equa- 

 torial" storm of March 22, 1903. Though not large, they appeal to 

 the eye in all the horizontal force curves of Birkeland's plate, including 

 that for Kew. Now turn to the next sKde, which reproduces the 

 simultaneous Antarctic record. Here we have two oscillatory move- 

 ments absolutely coincident in time, according to my own measure- 

 ments, with the oscillations recorded at Kew, but whilst movements 

 can be seen in the vertical force, these are small compared to those 

 in the dechnation. This is by no means the only case in which 

 movements ascribed by Birkeland to " equatorial " storms were syn- 

 chronous with well-marked movements in the Antarctic, and the 

 Antarctic movements in the horizontal plane were generally not less 

 but considerably larger than the movements at stations in temperate 

 or equatorial latitudes. 



§21. The next slide shows a good example of Prof. Birkeland's 

 "polar elementary" storm which occurred on February 10, 1903. 

 The subsequent slides illustrate various types of disturbance recorded 

 in 1902 and 1908 by the magnetographs in the charge of Mr. L. 0. 

 Bernacchi, the physicist of the National Antarctic Expedition. They 

 include specimens of what I have called the special type of disturbance, 

 of which numerous examples occurred in the midwinter months, usually 



