4 BIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, igO2 1903. 



him, to Hammerfest, and went to the hospital ('). I remained at Gargia to await an opportunity of going 

 with the guide to look for our things, the instruments in particular. The first time we set out on the 

 search, the wind was so high that we had to come down again. 



The journey back down the Beskades hills with fresh reindeer, was the wildest piece of driving 

 one can imagine. The animals flew like the wind, and galloped along in places where a horse would 

 have gone carefully step by step. We had five reindeer fastened together in a raide, and I sat in the 

 last pulk, firmly lashed to it. Occasionally the pulk was thrown over the edge of the slope, notwith- 

 standing that I put on all the brake that I possibly could with my elbows, which were well protected 

 with fur. Once indeed my reindeer itself fell, wonderfully sure-footed though it was; but after being 

 dragged along by the others for a few moments, it managed to struggle to its feet without assistance. 

 The day after this unsuccessful attempt, we once more went up. There was a little wind in the 

 morning, very much as it had been on the gth; but this time, instead of increasing, it gradually dropped 

 as we ascended; and when we began to beat up and down in the neighbourhood of the place in which 

 our things might be supposed to be, the sun shone out brightly, and there was no more wind than that 

 the Finn could light his pipe. 



We found the things at last, nearly all of them buried in the snow, scarcely more than one 

 kilometre from Lodikken hut, where we had thought of staying. 



We dug out nearly all our things, and got safely back to Gargia with them. 



That evening there was bright aurora, and I therefore unpacked some instruments, and had the 

 good fortune to make an interesting observation, which I have described in the report of my 2nd 

 aurora expedition ( 2 ). 



We had previously, also on our first expedition, made a very interesting observation of a rare, 

 but very significant, auroral phenomenon, which I will here briefly describe. To myself it is of special 

 interest from the fact of its being my first auroral observation of any importance. Moreover it immedi- 

 ately appeared to me that the observation was a confirmation of the hypothesis put forward by me in 

 1896 regarding the origin of the aurora, namely that the northern lights are due to cathode rays or 

 similar rays emitted by the sun, these rays being drawn in from space towards the earth by the terrestrial- 

 magnetic forces. 



It was ten minutes to six on the evening of the 5th February, when we were some miles from 

 Hammerfest, the weather clear and the moon shining, when there appeared a sharply-defined arc of light 

 from east to west through the zenith. From the very first, the arc was very intense, but very narrow, 

 right above our heads. Notwithstanding the bright moonlight, the aurora, which soon began to pass 

 through various phases of development with draperies and sheaves of rays, was visible up to half past 

 seven, when it disappeared. 



At Hammerfest the next day, the weather was just as clear; and at five minutes past six, the same 

 arc suddenly appeared again, though considerably fainter. Its manner of development and its disappear- 

 ance were so similar to those of the arc of the preceding day, that the phenomena left a decided 

 impression that the position of the sun or the moon in relation to the earth must play a direct part 

 in them. 



It may, as we know, not infrequently be seen in the registering of magnetic disturbances, not only 

 that well-defined perturbations reappear on two or more consecutive days, which in other respects may 

 be fairly calm magnetically, but that these well-defined perturbations can be so wonderfully uniform in 



(') HELLAND-HANSEN is now Director of the Biological Station at Bergen. 



( a ) Expedition Norv6gienne de 18991900 pour 1'etude des aurores bordales, par KR. BIRKELAND, p. 76. Videnskabs- 

 Selskabets Skrifter 1901, No. i. 



