12 



AKSEL S. STEEN. 



I.-N. Kl. 



time of the equinoctial months, and diminishes towards the solstices. On 

 the other hand, the quantitative effect of the sun, which is represented 

 by the area of the diagrams or the mean vector, is naturally greatest in 

 the summer and smallest in the winter. 



III. 



In accordance with the principles I have here laid down for a rational, 

 systematic investigation of the diurnal variation of terrestrial magnetism, 

 I have gone through the series of hourly observations from the polar 

 year, and have been fortunate enough to find a continuous calm period of 

 no less than 48 hours just at the equinox, namely, the time from midnight 

 on the 1 8th March, 1883, to 11 p. m. on the 20th, Göttingen time. In 

 addition to observations from the 12 polar stations proper, I have also 

 been able to use observations from Pawlowsk, Wilhelmshaven, Vienna, 

 Tiflis, Zi-Ka-Wei, and Los Angeles; while it has unfortunately been 

 impossible to find published simultaneous observations from any tropical 

 station. 



The following table gives a general view of the latitude of the sta- 

 tions, ^, their longitude from Greenwich, I, and their difference in time 

 from that of Göttingen, /, to the nearest tenth of an hour. 



Tab. 1. 



Station 



Cape Thordsen 

 Ssagastyr. . . . 

 Novaja Zemlja 

 Point Barrow 

 Jan Mayen . . 

 Bossekop . . 

 Sodankylä. . 

 Kingua Fjord 

 Godthaab . . 

 Fort Rae . . 

 Pawlowsk . . 

 Wilhelmshaven 

 Vienna . . . 

 Tiflis .... 

 Los Angeles. 

 Zi-Ka-Wei. . 

 South Georgia 

 Cape Horn. . 



78°24'N 



73 23 

 72 23 

 71 iS 

 71 o 

 69 58 



67 55 

 66 36 

 64 1 1 

 62 39 

 59 4' 

 53 32 

 48 15 



41 43 

 34 3 

 31 12 



54 31 



55 31 



15^ 

 126 



52 



156 



8 



23 

 26 

 67 

 51 

 US 

 30 

 8 

 16 



44 



iiS 



121 



36 



68 



26 



hrs. 

 0-4 E 

 7-8 E 

 2*9 E 

 I ri W 



1-2 W 



o'9 E 

 ri E 

 5-2 W 

 4-1 W 

 S-4 W 

 1-4 E 

 o-i W 

 o'4 E 

 2'3 E 

 8-6 W 



7*4 E 

 3-1 W 

 5-2 W 



