NORTHERN LIGHTS. 



motions of the needle over extensive circles, 

 without there being any necessity for explo- 

 sions, for luminous effusions from the pole to 

 the equator, or from one pole to another, in or- 

 der to restore the equihbrium. 



He who would have all the particulars of the 

 phenomenon embraced in one picture, should 

 have the origin and course of a complete ap- 

 pearance of the northern lights set before him. 

 Deep on the horizon, nearly m the situation 

 where it is intersected by the magnetic merid- 

 ian, the heaven, up to this moment clear, 

 grows black. There is a kind of hazy bank or 

 screen produced, which rises gradually, and at- 

 tains to an altitude of from 8 to 10 degrees. 

 The colour of the dusky segment passes over 

 into brown or violet. Stars are visible in it, 

 but they are seen as in a portion of the sky ob- 

 scured with dense smoke. A broad bright 

 luminous arc or seam, first white, then yellow, 

 bounds the dusky segment ; but as the brilliant 

 bow arises later than the sn^oky-grey segment, 

 it is impossible, according to Argelander('"), to 

 ascribe the latter to the effect of mere contrast 

 with the bright luminous border. The highest 

 point of the luminous arc, when it has been 

 carefully measured(**^), has usually been, found 

 to be not exactly in the magnetic meridian, but 

 to vary between 5 and 18 degrees from it, to- 

 wards the side on which the magnetic dechna- 

 tion of the place of observation lies. In high 

 northern latitudes, very near the north pole, the 

 smoky-looking spherical segment appears less 

 dark ; sometimes it is even entirely absent. In 

 the situation, too, where the horizontal force is 

 least, the middle of the luminous. arc is seen to 

 depart farthest from the magnetic meridian. 



The luminous bow, in constant motion, flick- 

 ering and changing its form incessantly, some- 

 times remains visible for hours before anything 

 like rays and pencils of rays shoot from it, and 

 rise to the zenith. The more intense the dis- 

 charges of the northern lights, the more vividly 

 do the colours play from violet and bluish-white, 

 through every shade and gradation, to green 

 and purplish-red. In our ordinary electricity 

 produced by friction, in the same way, the spark 

 first becomes coloured when the tension is high, 

 and the explosion is violent. The magnetic 

 fiery columns shoot up at one time singly from 

 the luminous arch, even mingled with black 

 rays, like thick smoke ; at another, many col- 

 umns arise simultaneously from several and op- 

 posite points of the horizon, and unite in a 

 flickering sea of flame, to the splendour of which 

 no description can do justice, and whose lumi- 

 nous waves assume another and a different 

 shape at every instant. The intensity of the 

 northern light is at times so great, that Lowe- 

 norn perceived its oscillations, in bright sun- 

 shine, on the 29th of January, 1786. The mo- 

 tion increases the brilliancy of the phenomenon. 

 Around the point of the vault of heaven which 

 corresponds with the direction of the dipping 

 needle, the rays at length collect together, and 

 form the corona or crown of the northern lights. 

 This surrounds the summit, as it were, of a 

 vast canopy, the dome of heaven, with the mild 

 radiance of its streaming but not flickering rays. 

 It is only in rare instances that the phenomenon 

 proceeds the length of forming the corona com- 

 pletely. With its appearance, however, the 



whole is at an end. The rays now become 

 rarer, shorter, less intensely coloured. The 

 crown and the luminous arches break up. By 

 and by nothing but broad, motionless, and al- 

 most ashy-grey, pale gleaming fleecy masses, 

 appear irregularly dispersed over the whole 

 vault of heaven ; these vanish, in their turn, 

 and before the last trace of the murky fuligin- 

 ous segment, which still shows itself deeply on 

 the horizon, has disappeared. Of the whole 

 briUiant spectacle, nothing at length remains 

 but a white delicate cloud, feathered at the 

 edges, or broken up, as a cirro-cumulus, into 

 small rounded masses or heaps, at equal dis- 

 tances. 



This connection of the polar light with the 

 most delicate cirrus-clouds, deserves to be par- 

 ticularly mentioned ; inasmuch as it shows us 

 the electro-magnetic evolution of light as part 

 of a meteorological process The terrestrial 

 magnetism here manifests itself in its effects 

 upon the atmosphere, in a condensation of the 

 watery vapour which it holds dissolved. The 

 observations, made in Iceland by Thienemann, 

 who regards the cirro-cumulus, or divided fleecy 

 cloud, as the substrate of the northern lights, 

 have been confirmed in later times by Frankhn 

 and Richardson, near the North American mag 

 netic pole, and by Admiral Wrangel, on the Si- 

 berian coasts of the icy sea. All observed 

 " that the northern lights sent forth the most 

 brilliant fays when masses of cirro-stratus 

 floated in the upper regions of the atmosphere ; 

 and when these were so thin, that their pres- 

 ence was only known by the formation of a 

 halo about the moon." These light clouds oc- 

 casionally arranged themselves, by day, in the 

 same manner as the rays of the Aurora, and 

 had the same effect as these in disturbing the 

 magnetic needle. After a grand nocturnal dis- 

 play of the northern lights, the same streaks of 

 clouds that had been luminous over night, were 

 discovered in the morning arranged in the same 

 manner('"). The apparently converging polar 

 zones of clouds (streaks of clouds, in the direc- 

 tion of the magnetic meridian), which constant- 

 ly attracted my attention in the course of my 

 travels on the lofty platforms of Mexico, as well 

 as in Northern Asia, belong apparently to the 

 same group of diurnal phenomena(^**). 



Southern lights have been frequently seen in 

 England by that able and diligent observer, Dal- 

 ton ; northern lights in the southern hemisphere, 

 as low as 45° of latitude (Jan. 14, 1831). In 

 instances that are not very rare, the magnetic 

 equilibrium is disturbed at both poles simultane- 

 ously. I have distinctly stated that northern 

 polar lights are seen within the tropics, even as 

 far south as Mexico and Peru. It is necessary 

 to distinguish, however, between the sphere of 

 a simultaneous apparition of the phenomenon, 

 and the zone of the earth in which the phe- 

 nomenon is displayed almost every night of the 

 year. As each observer sees his own rainbow, 

 so also, doubtless, does he see his own polar 

 light. A great portion of the earth engenders 

 the radiating Light-phenomenon at the same 

 time. Many nights can be mentioned in which 

 it was observed simultaneously in England, in 

 Pennsylvania, in Rome, and in Pekin. When 

 it is maintained that the northern lights decline 

 with the decrease of latitude, this must be un- 



