130 



NA TURE 



[June 8, 1882 



certain definite positions will tell us what substances are 

 present. Now, in 1S71 rings were seen, and they were 

 very bright. In 1S78 no ring whatever was seen. The 

 question to be decided, then, was, Did this year's eclipse 

 resemble in this respect the eclipse of 187 1 or 1878 ? The 

 result of the inquiry was that there were rings, but that 

 they took time to see. This indicated a solar condition 

 more resembling that presented in 1871 than in 1878, but 

 stopping short of it. 



Owing to these difficulties, hardly had Mr. Lockyer 

 time to pass back to the telescope by means of which the 

 spectrum of the corona was to be studied, when the clock 

 showed that sixty-five seconds had elapsed, and Mr. 

 Buchanan's "over" filled all with regret that the pheno- 

 menon, so rare and beautiful, and full of such precious 

 knowledge, which each was doing hh "level best'' to 

 secure, should be so ephemeral. So the caps were put on 

 the cameras by Dr. Schuster and his assistant, Mr. 

 Woods, lest the precious records which it was hoped 

 might have been secured thould be spoiled by the first 

 beam of the reappearing sun. It turned out, however, 

 that so admirably had the eclipse been calculated, and so 

 exactly had the French party hit upon the central line, 

 that the totality really lasted 7 seconds more, that is, the 

 full 72 seconds. The spectrum of the corona, therefore, 

 was studied for a second or two under, perhaps, better 

 conditions than had ever been present before, excepting 

 during the memorable observation of Janssen in 1S71. 

 There were the red and green and blue lines stretching 

 right across a wide field of view, and although no obvious 

 dark lines were seen in the momentary glimpse, it was 

 obvious that the spectrum was not truly a continuous 

 one. There were variations of intensity here and there, 

 and not the equal toning generally observed. So then 

 ended the totality in one of the observatories. Dr. 

 Schuster and his assistants at once proceeded to the ex- 

 temporised dark room on board the steamer to develop 

 the photographs, while those members of all the parties 

 who had made telescopic or spectroscopic observations 

 retired to the solitude of their tents to write down their 

 results while they were still fresh in their minds. 



Later on in the day there was a conference, at which 

 the collective note, which I have already telegraphed to 

 you, was drawn up and signed on behalf of the several 

 expeditions. The observations were thought then, and 

 are thought now, to have been a splendid success. The 

 photographic results obtained by Capt. Abney's rapid 

 plates have secured permanent records of the highest 

 value, which largely increase our knowledge of the sun's 

 atmosphere. They connect the spectrum of the sun with 

 that of the stars in a most unmistakable manner ; and, 

 taken in connection with the observations of Lockyer 

 and Trt5pied on the bright lines visible before totality — 

 observations predicted a year ago in the teeth of received 

 opinion — show that those who would explain solar phe- 

 nomena in the light of terrestrial chemistry have their 

 work cut out for them. But on this and on some other 

 matters I may have something to say in a subsequent 

 letter. 



The Cairo Correspondent of the Daily News telegraphs 

 on Monday : — 



By order of the British Government, Sir E. Malet has 

 officially thanked the Khedive for the great attention and 

 services rendered to the Eclipse Expedition. The Khedive 

 has returned a complimentary answer. No other Consul 

 has yet thanked his Highness. 



AURORA IN GREENLAND' 

 C INCE the publication of the researches on Aurora; by 

 *~ > Baron Nordenskjold, the study of this enigmatical 

 phenomenon has acquired still more attraction for the 



1 "Dm Nordlysets Perioder, efter Iakttagelser fra Godthaab i GrOnland." 

 Af Sophus Tromholt. (Publication of the Danish Meteorological Institute.) 

 Copenhagen, 1882. 



student of the physics of the globe. We are glad, there- 

 fore, to notice the appearance of a new work on 

 "Aurora?," published by the Danish Meteorological In- 

 stitute, being a discussion, by M. Sophus Tromholt, 

 of the fifteen years' observations (1865- 1880) made by 

 M. S. Kleinschmidt at Godthaab in Greenland. 



The auroras at Godthaab are seen, of course, almost 

 exclusively in the southern part of the sky. " I do not 

 remember," M. Kleinschmidt says, "to have seen during 

 these last twenty-five years, more than a few times, any 

 aurora in the north ; the middle point of the aurora-arc is 

 usually situated between due south and south-south-east, 

 with small oscillations on both sides of this middle point. 

 In all colonised parts of the western coast of Greenland, 

 the aurora; are always seen towards the south ; but it 

 seems to me that at the southern extremity of this country, 

 I have observed more intense aurora; extending through- 

 out the whole of the sky." This observation fully confirms 

 the conclusions of Baron Nordenskjold, as will be seen from 

 his map, which we reproduced (Nature, vol. xxv. p. 371). 

 Godthaab being situated in 64 n' N. lat., that is, in the 

 third region of Nordenskjold, the exterior circle of the 

 glory must appear as a bow in the south, and the common, 

 or interior one, as a luminous arc in the magnetic north, 

 or, rather, as a light spread throughout the sky. Indeed, 

 northern auroras were seen at Godthaab only during 

 twenty-five days, out of fifteen years, and their number 

 was but forty in the morning hours, and sixteen in the 

 evening. At Jacobshavn (69° 13' N.lat.) 50 per cent, of 

 all aurora; are seen towards the south east, 26 per cent, 

 towards the east, and only 9/5 per cent, appear in that 

 part of the sky which is comprised between north-west 

 and north-east. At Upernivik (72" 47' N. lat.) the dis- 

 proportion is still greater, 74 per cent, of aurora; appear- 

 ing between south-east and south, 145 towards the east, 

 and only 48 per cent, between north and west. As to 

 the frequency of the quiet arc-aurora (the "glory'' of 

 Nordenskjold), as compared with that of the brilliant ray- 

 aurora;, it is difficult to judge by the abstracts of observa- 

 tions published by M. Tromholt, inasmuch as the observer 

 seems not to have attached great importance to this 

 difference ; but it results from what he says that 

 the most frequent shape is that of a luminous arc 

 " whose rays are diffused so that the luminous 

 mass seems to be homogenous.'' The rays are often 

 only pulsations in the arc itself. As to the fascinating 

 and brilliant ray-aurora;, they are by far less frequent 

 than the former ; however — in accordance with Norden- 

 skjold's theory — they are not uncommon in this latitude. 

 The height of the middle point of the arc is usually from 

 5° to io c above the horizon. Feeble light, very much like 

 twilight, is not uncommon, as well as a similar light 

 spread throughout the sky. M. Kleinschmidt has also 

 observed aurora; in the shape of "an immense column of 

 smoke," consisting of more or less defined rays : " it 

 nearly always appears in the same position, starting from 

 a point between north-east and east-north-east, whence it 

 crosses the zenith and reaches an opposite point of the 

 horizon." The same was observed in the " common arc " 

 by Nordenskjold (NATURE, vol. xxv. p. 369, Fig. 5). 



The number of aurora; extending beyond the zenith, or 

 appearing in the northern part of the sky being anything 

 but numerous, it is only with caution that we may admit 

 the conclusion arrived at by M. Tromholt as to a 

 periodicity in the oscillations of the "auroral belt ;" but 

 it is worthy of notice that his conclusion is the same as 

 that arrived at by Weyprecht, namely, that " the auroral 

 belt advances towards the south about the autumnal 

 equinox, then moves towards the north, and reaches its 

 most northern position about the winter solstice ; thence 

 it again moves towards the south, and occupies its most 

 southern position about the spring equinox ; after that 

 it again returns towards the north." If confirmed by 

 more extensive observations, this result would imply an 



