432 



HIRKEI.AND. THE NORWEGIAN AURORA POLARIS EXPEDITION, 1QO2 1903. 



TABLE LXIII. 

 Values of Po for a current-system corresponding to A," = 270. 



Values of Py for a current-system corresponding to /\u 270. 



Values of Pia for a current-system corresponding to /\/ii = 270. 



We have moreover shown these three fields of force on charts, one for each field separately, and 

 one giving the field for two simultaneous systems of the first kind, one in the north and the other in 

 the south. 



The fields of force in these charts are not represented by current-arrows as in the perturbations, 

 but by current-lines (equipotential lines, see p. 85) and by lines of force for the horizontal components. 

 Lines have moreover been drawn on another chart for constant values of Po. 



In order to construct the former of these easily, when the force components at various places on 

 the earth have been calculated, the following mode of procedure has been adopted. 



P 9 

 The relation f. was determined for the various points at which the force-components were cal- 



Pin 



culated, this relation being a measure for the angle that the horizontal force-component forms with the 

 circles 6 = const, or 10 const. These we may call, for the sake of brevity, parallel circles and meri- 

 dians. We next drew curves for the various meridians and parallels, showing how this condition varied 



