196 COSMOS. 



ill the immediate vicinity of the magnetic pole, the smoke-hkfj 

 conical segment appears less dark, and sometimes is not even 

 seen. Where the horizontal force is the weakest, the middle 

 of the luminous arch deviates the most from the magnetic 

 meridian. 



The luminous arch remains sometimes for hours together 

 flashing and kindling in ever-varying undulations, before rays 

 and streamers emanate from it, and shoot up to the zenith. 

 The more intense the discharges of the northern liffht, the 

 more bright is the play of colors, through all the varying gra- 

 dations from violet and bluish white to green and crimson. 

 Even in ordinary electricity excited by friction, the sparks are 

 only colored in cases where the explosion is very violent after 

 great tension. The magnetic columns of flame rise either 

 singly from the luminous arch, blended with black rays simi- 

 lar to thick smoke, or simultaneously in many opposite points 

 of the horizon, uniting together to form a flickering sea of 

 flame, whose brilliant beauty admits of no adequate descrip- 

 tion, as the luminous waves are every moment assuming new 

 and varying forms. The intensity of this light is at times so 

 great, that Loweiiorn (on the 29th of June, 1786) recognized 

 the coruscation of the polar light in bright sunshine. Motion 

 renders the phenomenon more visible. Round the point in 

 the vault of heaven which corresponds to the direction of the 

 uiclination of the needle, the beams unite together to form the 

 so-called corona, the crown of the northern light, which en- 

 circles the summit of the heavenly canopy with a milder ra- 

 diance and unflickering emanations of light. It is only in 

 rare instances that a perfect crown or circle is formed, but on 

 its completion the phenomenon has invariably reached its 

 maximum, and the radiations become less frequent, shorter, 

 and more colorless. The crown and the luminous arches 

 bre&k up, and the whole vault of heaven becomes covered 

 with irregularly-scattered, broad, faint, almost ashy-gray lu- 

 minous immovable patches, which in their turn disappear, 

 leaving nothing but a trace of the dark, smoke-like segment 

 on the horizon. There often remains nothing of the whole 

 spectacle but a white, delicate cloud with feathery edges, or 

 divided at equal distances into small roundish groups like cir- 

 ro-cumuli. 



This connection of the polar light with the most delicate 

 >irrous clouds deserves special attention, because it shows that 

 .Jie electro-magnetic evolution of light is a part of a meteoro- 

 i)\,y cal process. Terrestrial nvagrietism here man. tests its in- 



