POLAR LIGHT. 147 



erence to -the movements which depend upon geographical 

 relations of place, and diurnal and annual periods. The ex- 

 traordinary disturbances which were first observed in the dip 

 are, as Halley conjectured, and as Dufay and Hidrter recog- 

 nized, in part forerunners, and in part accompaniments of 

 the magnetic polar light. I have already fully treated, in 

 the Picture of Nature, of the peculiarities of this luminous 

 process, which is often so remarkable for the brilliant dis- 

 play of colors with which it is accompanied ; and more re- 

 cent observations have, in general, accorded with the views 

 which I formerly expressed. "The Aurora Borealis has 

 not been described merely as an external cause of a disturb- 

 ance in the equilibrium of the distribution of terrestrial mag- 

 netism, but rather as an increased manifestation of telluric 

 activity, amounting even to a luminous phenomenon, exhib- 

 ited on the one hand by the restless oscillation of the needle, 

 and on the other by the polar luminosity of the heavens." 

 The polar light appears, in accordance with this view, to be 

 a kind of silent discharge or shock as the termination of a 

 magnetic storm, very much in the same manner as in the 

 electric shock the disturbed equilibrium of the electricity is 

 renewed by a development of light by lightning, accompa- 

 nied by pealing thunder. The reiteration of a definite hy- 

 pothesis in the case of a complicated and mysterious phenom- 

 enon has, at all events, the advantage of giving rise with a 

 view to its refutation to more persistent and careful observa- 

 tions of the individual processes.* 



Dwelling only on the purely objective description of these 

 processes, which are mainly based upon the materials yielded 

 by the beautiful and unique series of observations, which 

 were continued without intermission for eight months (1838, 

 1839) during the sojourn of the distinguished physicists, 

 Lot tin, Bravais, and Siljestrom in the most northern parts 

 of Scandinavia,! we will first direct our attention to the sor 



* Cosmos, vol. i., p. 193-203; and Dove, in Poggend., Annalen, bd. 

 xix., s. 388. 



t The able narrative of Lottin, Bravais, Lilliehook, and Siljestrom, 

 who observed the phenomena of the northern light from the 19th of 

 September, 1838, till the 8th of April, 1839, at Bossekop (69 58' N. 

 lat.) T in Finmark, and at Jupvig (70 6' N. lat.), was published in the 

 fourth section of Voyages en Scandinavie, en Laponie, au Spitzberg et 

 aux Feroes, sur la Corvette, la Recherche (Aurores Boreales). To these 

 observations are appended important results obtained by the English 

 superintendent of the copper mines at Kalfiord (69 56' IS. lat.), p. 

 401-435. 



