48 Prof. L. Vegard : Results of Northlight Investigations 



1910"*, an expedition to the same place was undertaken by 

 the writer, mainly for the purpose of determining the prin- 

 cipal lines of the auroral spectrum f . At the same time 

 parallactic photographs were taken in cooperation with 

 Director Krogness at the Haldde observatory % with a base- 

 line of 12*5 km., or about three times as long as that used by 

 S termer in 1910, With this longer basis the results of 

 Stunner from 1910 were so far confirmed in that nearly the 

 same average height of the aurora was found (108*2 km.), 

 but the very small heights down to 40 km., which in some 

 cases were found by St^rmer in 1910, were not found by us. 

 In all cases treated by us, the height of the bottom edge 

 varied between 81 and 137 km. In the same year 

 K.Wegener observed at Spitsbergen with a base-line 10' km. 

 and found heights varying between 70 and 200 km. 



In the spring of 1913 St0rmer undertook a second ex- 

 pedition to Bossekop, and at this time he photographed 

 simultaneously from the two stations Bossekop — Store 

 Korsnes, 27*5 km. apart. 



Stunner has also succeeded in collecting a most valuable 

 material of parallactic photographs from somewhat lower 

 latitudes during later years. 



A complete account of the results derived from this 

 material is not yet published, but some results have appeared 

 in preliminary communications. The heights found vary 

 between 86 and 325 km., in good agreement with the results 

 found by Krogness, the writer, and by Wegener. The 

 greatest number of heights he finds between 90 and 130 km. 



Since the Haldde observatory in Finmarken was erected 

 in the year 1912 a considerable material of auroral observa- 

 tions has been collected by Director 0. Krogness. These 

 observations, mainly consisting of more than 400 successful 

 parallactic photographs from the year 1914, have been 

 worked out by the writer at the Physical Institute of 

 Christiania. 



A complete account of the results is to be found in a work 

 by Mr. Krogness and thn writer, which has recently appeared 

 in the series of publications issued by the Geophysical 

 Commission of Norway §. 



With regard to details I must refer to this work. It is 



* C. S termer, "Bericht iiber eine Expedition nach Bossekop etc.," 

 Vid. Selsk. Skr. Christiania, 1911. 



t L. Vegard, " Bericht iiber eine Expedition nach Finmarken 1912-13," 

 Vid. Selsk. Skr. Christiania, 1916. 



\ O. Krogness & L. Vegard, " Hohenbestimniungen des Nordlichts 

 etc.," Vid. Selsk. Skr. Christiania, 1914. 



§ L. Vegard & Krogness, "The Position in Space of the Aurora 

 Polaris," Geofysiske Publikationer, vol. i. no. 1, Christiania, 1920. 



