712 TEREESTEIAL MAGNETISM. 



which had been obtained previous to the German and Swedish 

 Expeditions. 



Sir Edward Sabine has shown that the theory of Halley, which 

 was put forth in 1683, is the theory which is supported by recent 

 observations, viz., that " the globe of the Earth may be regarded as 

 " one great magnet, having four magnetic poles, two of them near 

 ** each pole of the equator, and that in those parts of the world 

 " which lie near any of those magnetic poles the needle is chiefly 

 " governed thereby, the nearest pole being always predominant 

 " over the more remote." 



The work of Hansteen, ** Magnetismus der Erde," published in 

 1819, of which an abstract was published in British Association 

 Report for 1835 by Sir Edward Sabine, and this work of Sabine 

 just published complete our knowledge of the magnetic conditions 

 of the northern regions up to the present time. 



The results which have been obtained are collected at the end 

 of the paper in groups for convenient comparison with the phenomena 

 which may be observed at future periods. 



VIII.— THE AURORA BOREALIS. 



1 . Observations of Aurora at Melville Island. (Parry's 

 First Voyage, &c.) 



A brilliant display of Aurora seen on Jan. 1 5 is described by 

 Captain Sabine. It began with an arch nearly north and south, 

 a little east of the zenith. " Towards the southern horizon was 

 *' the ordinary Aurora, giving a pale light, apparently issuing 

 " from behind an obscure cloud, at from six to twelve degrees of 

 " altitude." 



" The luminous arch broke into irregular masses, streaming 

 *' in different directions, varying in shape and intensity, and 

 *' always to the east of the zenith, and was most vivid to the 

 « E.S.E." 



*' The various masses seemed to arrange themselves in two 

 " arches, one passing near the zenith, and a second midway 

 " between the zenith and the horizon both north and south, but 

 " curving towards each other." " At one time a part of the arch 

 " near the zenith was bent into convolutions like a snake in 

 " motion, and undulating rapidly." The light was estimated as 

 equal to that of the moon when a week old. Besides the pale 

 light, which resembled the combustion of phosphorus, a very 

 slight tinge of red was noticed when the Aurora was most vivid, 

 buf no other colours were visible. 



On the next day it blew a fresh gale from N.N.W. 



The Aurora had the appearance of being very near us, but no 

 sound could be heard. The Aurora was repeatedly seen on the 

 following day, assuming the shape of a long low arch, from 3° to 

 12° high in the centre, extending from south to north-west The 

 temperature at this time was —36° F. 



