NATURE 



43: 



THL'RSDAV, MARCH lo, 1S87 



THE AURORA BO RE A US 

 L'Aurore Borealc. Atude getu'rale des Phenomhies 



prodiiils par les Courants elcctriques de I'Atmosphire. 



Par M. S. Lemstrom. (Paris: Gauthier-Villars, 1886.) 

 Rcsultatc dcr Poliirtuht-Bcobachluitgen angestellt im 



Winter 1882 u/id 1&S2 nuf dcii Slationcn Kingua Fjord 



und Xain. Von Dr. K. R. Koch. (Berlin : A. Aslier 



and Co., 1886.) 

 ''r'HE organised and obstinate scientific curiosity of our 

 '- time has not neglected the beautiful phenomenon 

 of the " Polar Dawn." Yet its investigation is attended 

 by peculiar difficulties and discouragements. It can be 

 profitably conducted only amid scenes of frozen desola- 

 tion, in the grisly depths of Arctic winter nights, under 

 conditions taxing man's energy and resource to live, to 

 say nothing of observing. The appearances in ciuestion 

 are, moreover, as elusive as they are surprising. They 

 promptly kindle the imagination, but leave the under- 

 standing, unless prepared by special study to apprehend 

 something of their causes, balfied and helpless. Never- 

 theless, auroral research, though Nature seem to frown 

 upon it, has been pursued with indefatigable energy 

 during the last half century. It has formed the principal 

 object of some, it has occupied a prominent place in the 

 programmes of all recent Polar expeditions ; besides 

 being furthered, with less heroic zeal, by writers and 

 thinkers unequal or averse to the company of thermo- 

 meters normally below the zero of Fahrenheit. Nor have 

 these labours been thrown away. Much of the mystery 

 long attaching to the evanescent splendours of Arctic 

 skies has been dissipated. There is no longer any doubt 

 as to the kind of explanation appropriate to them. Their 

 laws and relationships have been, to a great extent, 

 elucidated ; a satisfactory theory of their origin is at 

 hand ; some circumstances of their occurrence, long in 

 debate, have been attested on unquestionable authority. 



An excellent specimen of the patient laboriousness by 

 which these results have been brought about is aftbrded 

 in the work of Dr. Koch, cited as one of our authorities. 

 He was in sole charge of the German station of Nain, on 

 the coast of Labrador, during the International Polar 

 term 1882-83, ^"d now presents us with the record of 

 his observations there, together with those made simul- 

 taneously at the still more northerly post of Kingua 

 Fjord. Although situated in about the latitude of 

 Dundee — 56' 33' — Nain appears to be, in point of 

 climate, one of the grimmest localities accounted habit- 

 able on the face of the globe. Frostbites were a quite 

 common incident of Dr. Koch's daily experience ; and 

 furious winds, rendering the use of his meteoroscope 

 impossible, often left him dependent upon the natural 

 features of the solemn but forbidding landscape, for 

 determining the azimuths of auroral bands and arches. 

 As regards these phenomena, indeed, the station is 

 admirably located. It lies close to the southern edge of, 

 if not actually within, the zone of maximum frequency ; 

 auroriu are consequently numerous and intense, and 

 appear almost indifferently above the northern or 

 southern horizon. Their varying forms are beautifully 

 Vol. XXXV.— No. 906 



delineated in the drawings which lend a greatly in- 

 creased value to Dr. Koch's publication. Multiple 

 arches, up to the number of eight, were frequently seen ; 

 and the incessant movements affecting them, both as a 

 whole and in their parts, the transverse flashing of the 

 rays set side by side to compose some of them, the tor- 

 rential rushing of light along the paths others seemed to 

 prepare for it, as well as the restless wanderings of the 

 entire luminous structure up and down the sky, gave 

 continual variety and animation to these strange ex- 

 hibitions, while accentuating their baffling recalcitrance 

 to exact measurement. No estimates of height were 

 attempted at either Nain or Kingua Fjord ; but there 

 was a total absence of auroral appearances below the 

 clouds, or otherwise unmistakably very near the earth, 

 such as have been noted by M. Lemstrom and other 

 observers in high latitudes. Luminous mists were, how- 

 ever, common. At times they suffused the whole sky ; 

 and shapeless masses of them constantly succeeded, and 

 (at Kingua Fjord) were often the substitutes for the 

 organised and definite forms of a perfect aurora. A 

 sudden and wide-spread development of cirrus clouds 

 was another curious secondary feature of the Nain polar 

 lights. These were, at both stations, completely mute ; 

 not a suspicion of audibility attended their movements. 



A no less intrepid observer than Dr. Koch is the 

 author of the work with which we have coupled his in 

 the heading of this article. M. Lemstrom's auroral re- 

 searches began in 1868, when he was attached to the 

 Swedish Polar Expedition commanded by Baron Nordens- 

 kjold. They were continued during a sojourn of six 

 weeks in Finnish Lapland in 1871, and were brought to a 

 highly successful issue at Sodankylii in 1882-84. Finland 

 held an honourable place among the eleven nations lately 

 combined for a simultaneous attack upon the secrets of 

 the Arctic circle ; and the Professor of Physics in the Uni- 

 versity of Helsingfors was, by an almost inevitable choice, 

 appointed chief of the Finnish meteorological station 

 established in compliance with the terms of international 

 agreement. Our readers are not unacquainted with the 

 original line of work struck out by him in that capacity. 

 Its upshot was to secure demonstrative evidence as to 

 ihe proximate cause of the aurora borealis. 



The book under review derives, then, a particular inter- 

 est from its authorship. It is the production of a man 

 who has devoted thought and labour without stint to the 

 subject of which it treats, and has pushed the associated 

 problems visibly nearer to solution. He now sums up 

 the present state of knowledge as regards them in a well- 

 arranged, concisely written, and copiously illustrated 

 volume, recapitulating the most significant and surely 

 established facts, fitting them, with the critical judgment 

 bought by long experience, into their proper places, and 

 expounding the theory best adapted to interpret and 

 harmonise them. 



Remarkably, as time went on, Halley's conjecture of a 

 magnetic origin for aurone gathered round it confirmatory 

 circumstances entirely unknown to its author. Celsius 

 and Hiorter noticed, in 1741, spasmodic disturbances of 

 the magnetic needle coincident with the darting move- 

 ments of northern lights. Wilcke, Ussher, and Dalton, 

 ascertained, towards the end of the century, the close 

 geometrical relations between the terrestrial magnetic 



