5 68 



NATURE 



{Oct. ii, 1883 



other half, the objective part, is constructed in open trellis 

 work, partly in order that the wire cross may easily be 

 seen when a lantern is held at its side, and partly on 

 account of the balance. The horizontal as well as the 

 vertical circle, is provided with noninus, whereby 10' is 

 read directly and 1' may easily be ascertained. To the hori- 

 zontal axis belongs a libella, on which each part represents 

 I'. A massive base of cast-iron — a vertical column with 

 three projectors at the foot, each one with a foot-screw — 

 gives the instrument an exceedingly solid rest, and keeps 

 the due level for weeks when the instrument is not sub- 

 jected to gales or other violent exterior influences. 1 lur 

 station possesses two such theodolites, while the Swedes 

 at Spitzbergen have three, the Dutch on board the Varna 

 two, and Dr. Sophus Tromholt, at Kautokeino, one. 



Auroras have been seen here during the winter almost 

 every night, and during all weathers, thus, even behind 

 cumulo-stratus clouds, oscillating waves of the aurora 

 borealis have at times been observed. Proper measure- 

 ments have, however, of course only been effected on 



clear nights. With Dr. Sophus Tromholt, who has, as 

 the readers of Nature know, from his communications 

 to this journal, during the winter sojourned at Kautokeino 

 specially for his researches on the aurora borealis, we 

 have arranged to measure at agreed periods the eleva- 

 tion of the aurora in the common plane Kautokeino- 

 Bossekop. We have effected a number of such mea- 

 surements here, which will, I believe, give important 

 results as regards this phenomenon, when compared with 

 those made by Dr. Tromholt. A closer auxiliary station 

 for parallax measurements was also contemplated here, 

 and to this end I had a pillar raised in an open place 

 for a theodolite, about seven kilometres south of our 

 station, but the want of telephonic connection and 

 assistants, I regret to say, prevented this project from 

 being carried out. 



The auroral forms or types which have appeared here 

 have been those generally known, from the grand corona 

 to the modest pulsating little luminous cloud, but as a 

 characteristic feature attending them all I must mention 



-The Norwegian Circumpolar Station at Bossekop. a, magnetic observatory ; b, vane ; c, rain-gauge ; d, black-ball thermometer ; 

 instrument ; /, auroral theodolite; £-, inslrume.it for recording the auroral observations. 



the absence of stability in the types. Thus only on a 

 few occasions has there been an opportunity of watching 

 the quiet stationary arc, but in general the aurorae have 

 represented wafting draperies and shining streamers with 

 ever-changing position and intensity. 



As often as there has been an opportunity, spectro- 

 scopic researches have been effected with a Wrede's 

 spectroscope. The well-known yellow-green auroral line 

 has always been observed, and on one occasion also the 

 red, the position of which we succeeded in fixing approxi- 

 mately in the spectroscope. 



The meteorological instruments with which we have 

 been furnished are similar to those in use at the meteoro- 

 logical observatory in Christiania. A Kew station- 

 barometer (Adie) is employed at the hourly observations, 

 while a Fortin barometer (Secretan) serves as normal and 

 control barometer. Generally a few times a week both 

 barometers, which hang parallel in the office of the station, 

 are compared. As a reserve instrument we have an 



aneroid, but this we have fortunately had no need of 

 using. 



For the protection of the thermometers we have 

 erected a wooden cage on four poles facing the north, 

 with blinds, a double back wall and a roof, exactly in 

 conformity with Wild's model. In the centre of the 

 cage is the actual thermometer box placed, of sheet iron 

 and with a free circulation for the air, in which is to be 

 found dry and wet thermometers (divided into o°'2 C), 

 as well as maximum and minimum ones. All the thermo- 

 meters, which were manufactured by Aderman of Stock- 

 holm, have several times during the winter been examined 

 as to the stability of zero, which has always been found 

 perfectly correct. Besides these a black-ball thermometer 

 has during the summer been erected, and read several 

 times a day. Psychrometer readings have on some occa- 

 sions been controlled at low temperatures by observations 

 with Allnard's modified form of Regnault's hygrometer 

 (Golaz, Paris), while absolute determinations of moisture 



