6o 



NATURE 



{May 17, 1883 



miles south of the signal usually drawn on the maps of 

 the delta of the Lena. Three days later the expedition 



chose Sagastyr Island as the place for the station, and 

 began to erect the building and arrange the instruments. 



Russian Meteorological Station at Sagastyr, at the mouth of the Lena, 73° 22' 30" N. lat., 144° 14' 46" E. long. 



The house of the station is obviously very small ; and 

 when looking at Mr. Schtitze's sketch of this small build' 



tion with the civilised world, one cannot but admire the 

 devotion of those who have willingly submitted to remain 



ir.g, lost amidst the snow-plain, far from any communica- in these inhospitable latitudes for scientific purposes 



THE AURORA BOREALIS 



AMONG the numerous varieties of the aurora borealis 

 or northern light, there is one of particular interest 

 as regards the determination of the origin of this pheno- 

 menon. This variety, which was observed and reported 

 upon in 1868 by the members of the Swedish Polar 

 Expedition, takes the form of tiny flames or a phosphor- 

 escent luminosity, appearing during the winter months in 

 the Polar regions, around projecting objects, viz. moun- 

 tain cones and ridges. This phenomenon is so prominent 

 that one need no: be a scientist to discover it, and it was 

 observed by our well-known philologist, Herr M. A. 

 Castrdn, during his journeys in Siberia. Herr Castren's 

 descriptions of the phenomenon are very minute, and 

 exactly in accordance with its usual appearances, but his 

 observations were, however, not known to me in 186S, 

 and it was only on the return of the expedition that I 

 heard of them. The observations made by the Swedish 

 expedition at Spitzbergen led the Finnish Society of 

 Science in 1871 to despatch an expedition, of which I was 

 a member, to Lapland to ascertain if such a phenome- 

 non could not be called forth, or at all events magnified, 

 by mere mechanical appliances. And assuming that the 

 aurora borealis in general, and the variety of the same 

 just mentioned in pariicular, is caused by electric currents 

 in the atmosphere, an apparatus of the following nature 

 was erected on Luosmavaara, a mountain-top about 520 

 feet above the surface of the Lake Enare, in Lapland. 

 It consisted of a number of fine points of copper wire 

 laid out in the shape of a wreath two square metres in area, 

 and connected by a circular wire of the same metal. This 

 wreath was attached to a long pole, from the top of which 

 a single copper wire (0-4 mm. in diameter) led to a gal- 

 vanometer fixed in a room in the Enare vicarage, some 

 two miles distant east, and from the galvanometer 

 another copper wire led to a disk of platina in the earth. 



When this circuit was closed, the galvanometer gave a 

 deflexion, although faint. But on the very same night 

 the apparatus was erected, viz. November 22, 1871, there 

 ai>teared an aurora, which began with a single perpendi- 



cular column of light above the top of the Luosmavaara! 

 This column was analysed with the spectroscope, and 

 gave the usual yellow-green line, but whether the 

 column was on or behind the mountain-top could unfor- 

 tunately not be clearly ascertained. That it, however, 

 had its origin from the apparatus described above appears 

 to me, after the researches were made which I am about 

 to detail, to be beyond a doubt. At the same time, on 

 November 22, 1871, it was observed, when studying the 

 spectrum of the flames which, on that day appeared 

 around the mountain-tops more distinctly than usual, that 

 the characteristic yellow-green line in the spectroscope 

 was returned from nearly every object, as, for instance, 

 the ice of a pond, the roof of a shed, and even, though 

 faintly, from the snow in the immediate vicinity of the 

 observatory. These observations led me to believe that 

 I was within a sphere of electric discharge, whose radius 

 extended considerably around the station. 



This interpretation of mine has, however, not been 

 generally accepted by students of the phenomenon, who, 

 on the other hand, have explained the appearance as 

 being an aurora reflected from the earth ; but that this 

 theory is erroneous will be clearly demonstrated by the 

 researches detailed below. 



In Baron Nordenskjold's exhaustive investigations of 

 the aurora borealis during the Vega expedition, he states 

 that he was unable to discover this phosphorescent phe- 

 nomenon which I have observed, and that he had noticed 

 in the spectroscope, in connection with the same, a faint 

 band near the line D ; but this has nothing whatever to 

 do with the auroral line. In order, however, to make it 

 clear that I have not confused the^e two lines, I may 

 state that already in 1S71 I observed the absorption-band 

 in question, as will be seen from my work at the time on 

 the aurora borealis and the auroral spectrum. In these 

 researches I determined the wave-length of this line, and 

 as the latter is only apparent in daylight or moonshine, 

 while my observations were without exception made in 

 the dark, it is perfectly clear that this line or band has 

 nothing in common with the auroral one. The two lines 

 are, in fact, of such a different character that they cannot 



