14 BIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, IQO2 1903. 



BUILDINGS. 



Upon the arrival of the expedition, the following buildings and contrivances were put up: 

 The terrestrial magnetic register-observatory. 

 The observatory for absolute determinations. 

 Hut for the registering of earth-currents. 

 Thermometer-hut. 

 Pillar for astronomical measurements, etc. 



The Terrestrial Magnetic Register-Observatory. 



This was a stone cellar, divided into two rooms, the outer of which served as an entry, the north, 

 inner room being the real observatory. (Plan Fig. 13). Here there were 4 stone pillars, the same as were 

 used in the polar year 1882 83, for the instruments and the registering apparatus. P, PI and PH, are 

 the pillars for the three instruments, PHI the one for the registering apparatus. L is the lamp reflector, 

 R the registering apparatus, V, D, and H the variometers for respectively the vertical intensity, declination, 

 and horizontal intensity, d 1 and dH are the two doors. 



The drawing beside the plan, on the magnetic meridian arrow, represents the position of the magnets 

 in the instruments in relation to the meridian. The magnets in the drawing are about one fifth of their 

 actual size. 



The Observatory for the Absolute Determinations. 



This observatory was a house of the same kind as that in Spitsbergen, the drawing of which will 

 therefore serve to illustrate this one. There was only one difference, namely that the stone pillar 

 upon which the various magnetic instruments and the earth-inductor were set when in use, was placed 

 in the middle of the house. The azimuth of the pillar was determined by triangulation, the pillar 

 forming one vertex of a triangle of which the two other vertices were the astronomical pillar (marked on 

 the map (i), and mentioned above under the heading 'Buildings'), and the spire of Kaafjord Church. 



Hut for the Registering of Earth-Currents. 



This hut was built of wood, and stood beside the magnetic register-cellar, as shown on the map. 

 The purpose of these earth-current investigations was to obtain photographic curves showing the varia- 

 tions in the earth-currents, especially during magnetic storms. 



Four insulated cables of a length of 200 metres were laid down in the directions north, east, south, 

 and west. Their ends were connected with the earth by filling deep holes with coal-dust, which was 

 pressed firmly down round a bright copper wire. 



In the register-house the two cables, north and south, were connected, with a suitable shunt, with 

 one galvanometer Deprez-d'Arsonval, and the east and west cables similarly connected with another 

 exactly similar galvanometer. The oscillations of the galvanometer were registered photographically. 



Unfortunately these galvanometers, supplied by Reiser & Schmidt, Berlin, were very bad, so that at 

 last, after prolonged trial, we had to reject one and replace it with one from Hartmann & Braun, of Frank- 

 fort. When subsequently we succeeded in obtaining good photograph curves, an electromagnetic con- 

 trivance for the time-marks was arranged for all magnetic and earth-current registerings, in order to 

 facilitate comparison with the magnetic curves. Down in the dwelling-house, by the side of the chro- 

 nometer, the time could be marked on all the photograms by pressing an electric button. This, espe- 

 cially during the rapid march of the registering apparatuses, was of very great importance. 



As it appeared that the earth-currents in Kaafjord had a predominant direction which seemed to 

 indicate that local conditions such as the proximity of the coast-line, etc., had something to do with it, 



