260 NOETH MAGNETIC POLE AND NORTHWEST PASSAGE. 



one respect, namely, that the magnetic poles are the points of mark on 

 the surface of the earth, and it is obvious that magnetic investiga- 

 tions just at these ]3oints, or in their immediate vicinity, must be of 

 the greatest interest to the science of terrestrial magnetism. The 

 Gauss theory by no means solves all the riddles presented by the 

 phenomena of terrestrial magnetism, but continual efforts are being 

 made to decipher these problems by the collection of as reliable and 

 comprehensive observations as it is possible to procure. 



The magnetic work of the Gjoa expedition is intended to be a con- 

 tribution to this object. But the difficulties were not small. The 

 very fact that horizontal intensity, as we have heard, becomes, in the 

 vicinity of the magnetic poles, so infinitesimally small, renders neces- 

 sary extraordinary precautions for the determination of this itself, 

 as well as of the variation. The Gjoa expedition's equipment of 

 instruments was calculated for this purpose. The magnets, fourteen 

 in number, were chosen with great care in Potsdam just before our 

 departure. The inclination we were able to determine by the help 

 of three inclinatoria of varying construction, and for the determina- 

 tion of the declination we had two different instruments. 



Added to these was a set of self -registering A^ariation apparatus; 

 that is to say, three instruments permanently erected in a dark room, 

 each instrument containing a small magnetic needle, two of the latter 

 being suspended by a fine quartz thread, the third oscillating on a fine 

 hearing in such a manner that the needle with its movements followed 

 the declination, the second the horizontal intensity, and the third the 

 inclination, even its minutest changes. Each needle was provided 

 Avith a looking-glass, which reflected the light from a lamp onto a 

 drum covered with photographic paper, which, by means of clock- 

 Avork, made one rcA^olution during the course of the tAventy-four 

 hours. It Avas arranged so that the reflection from each of the three 

 needles struck the drum at different heights and caused a little dark 

 spot, but Avhen the drum Avith its paper reA^olved, each of these spots 

 Avas continued, forming a consecutive dark line. There Avere thus 

 three dark lines across each other on the paper Avhen after the lapse 

 of twenty-four hours it was taken off. 



After Avhat Ave haA'e alread}^ heard, it Avill easily be understood 

 that it Avould not have done to select the pole itself for a permanent 

 obserA^ation station, cA^en had we known beforehand its exact situa- 

 tion, and could haA^e foreseen that it would keep immoA^able on one 

 of the same spor. Advised by Prof. Adolf Schmidt, I therefore 

 decided to make the base station, where the instruments for variation 

 Avere to be erected, at such a distance from the pole that the inclina- 

 tion would be about 89°. This requirement was fulfilled by Gjoa- 

 havn, Avhich accordingly became our headquarters. We constantly 

 made excursions hence to adjacent parts of the country, and right in 



