376 



BIRKELAND. THE NORWEGIAN AURORA POLARIS EXPEDITION, 1902 1903. 



local character, and the existence of large connected systems can hardly be proved with certainty. This 

 is clearly evident from Chart XII, for the hour I9 h 5o m . 



Two Charts, XIII and XIV, have been drawn for the last section of the perturbations of the day 

 under consideration, from about 22 h to the end of the period. The conditions are comparatively simple 

 and clear. On the night-side there is a powerful negative system of precipitation, which extends from 

 Ssagastyr westwards through the north of Europe to Godthaab and Kingua Fjord. At the two last- 

 named stations the direction of the current-arrows is a little peculiar. The principal axis of the system 

 seems to turn off towards the north rather abruptly. This seems to be analogous to the circumstance 

 we have so often observed before, namely, that the negative system turns up, on the afternoon-side, into 

 higher latitudes to the north of a positive system in the vicinity of the auroral zone (fig. 140 p. 327). 



At Fort Rae too, there is certainly a positive system, while the storm-centre of the negative system 

 is in the north of Europe. 



The current-arrow at Fort Rae, which should give the direction of the positive system of precipi- 

 tation, has, it is true, a rather marked southerly direction; but this is so nearly the opposite of what 

 we find during the ordinary negative storms here, that there seems no doubt that this is a positive 

 area of precipitation. 



TABLE LV. 

 The Perturbations of the I5th July, 1883. 



