650 BIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, 19021903. 



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The course of the intensity and extent of the discs round the sun and moon was analogous to 

 this in this district. 



The whole phenomenon was analogous, down to its smallest details, to that of the 3oth June or 

 ist July, 1908, which I have described in Astr. Nachr. 4266 Bd. 178, 1908. 



In a paper by D. STENQUIST (I. c., p. 14), which we only saw after the above was written, a 

 number of interesting observations have been collected from the period from the lyth to the 2ist Mav. 

 The author summarises his results as follows: 



"From the twilight-phenomena observed, from the abundant occurrence of cirri, in which corona 

 and halos were produced, and from the existence of aurora borealis, it would seem that the earth, at 

 the heliocentric passage, was enveloped by not inconsiderable quantities of cosmic dust (probably charged 

 with negative electricity)". 



Concerning the meteorological observations at the Haldde observatory and at Kaafjord during 

 transit, I will first of all emphasise the fact that many extremely characteristic polar bands were formed 

 in a striking manner, and in more rapid succession than I ever remember to have seen before. The 

 significance of such polar bands in connection with the theories here propounded, has been dwelt on in 

 an article "Sur la Formation des Nuages SupeYieurs", p. 75 of "Expedition Norvgienne de 18991900 

 pour 1'Etude des Aurores Bor6ales". It is assumed that the polar bands are produced by the in- 

 drawing, through terrestrial magnetism, of negative corpuscles from space in a manner similar to that 

 in which the corpuscle-rays that produce auroral arcs are drawn in. 



The weather on the i8th and igth May was very unfavorable for observing, as thick mist frequently 

 prevailed, with snow and ice-spicules in the air. Now and then, however, it was clear for some time, 

 for instance on the evening of the i8th up on Haldde Mt., and down in Kaafjord on the morning of 

 the igth, beginning from midnight. 



At about 8 p. m. on the i8th, I saw from the mountain at one time 4 parallel, very marked, 

 polar bands, curving from west to east over the northern sky, with their highest point about 30 above 

 the horizon. They changed considerably and developed rapidly, but were soon hidden by the mist. On 

 the morning of the igth, Krogness saw many cloud-formations of the same kind from Kaafjord, concer- 

 ning which he says: 



"Although the cloud-covering was not favorable for the observation of cirrus-clouds on the night 

 of the i8th May, there were several opportunities at Kaafjord of observing very peculiar cloud-forma 

 tions. There was a most unusually abundant variety of cirrus-bands. Their shape and mannu 

 forming showed an unmistakable resemblance to those of aurora. Great drapery-like clouds would fre- 

 quently appear quite suddenly, or large portions of the sky be covered with clouds in the form of a corona; 

 and more or less bright polar bands were continually visible. The following are some of the notes made 

 at the time (Gr. M. T. is employed) : 



May 18, 1910, n h 32 p. m. 6 polar hands in a direction WNW ESE passing the zenith and 

 north and south of it. 



34 35 m . Two or three small draperies were formed, which, however, soon disappeared. In the 

 southernmost band numerous stripes. 



39 m . A bright band suddenly makes its appearance a little north of the zenith. 



40. A tassel with striped figures appears, and spreads eastwards in the form of a drapery along 

 the above-mentioned polar band. 



Above the mountain in the west several faint, evenly luminous, very characteristic bands. In tl 

 north brighter bands with from 2 to 3 peculiar, bright, awl-shaped, striped figures pointing downwards 

 and westwards. These are almost due north. 



