302 



SCIENTIFIC RESULTS OF ZIEGLER POLAR EXPEDITION 



An inspection of the mean yearly ranges in diurnal variation for the stations of thie above 

 tabulation indicates that these ranges are in some way dependent upon the values of the respective 

 magnetic dips, the greater ranges being associated with the greater inclinations. Dr. Bauer* 

 has announced a law covering this apparent interrelation, namely, that the mean value, rf, for 

 the year of the total diurnal amplitude of the magnetic declination is a function of the mag- 

 netic latitude, y', which may be in the general case expressed mathematically as 



d=k secV'. 



in which the value of <p' is derived from the magnetic inclination, /, in accordance with the 

 well-known formula 



tan ^' = 0.5 tan I ; 



/fe is a constant depending upon the position of the particular series under discussion in the 

 sun-spot cycle. Dr. Bauer's preliminary value of k is 2. '58. Pending greater elaboration by 

 him it has seemed desirable in connection with above compilation to determine values of k by 

 grouping these stations in order of the approximate sun-spot frequencies given on page 297. 

 Accordingly values have been derived by the method of least squares from groupings of 

 stations as indicated in the following summary of results : 



The ranges for the individual stations of the groupings have been calculated using the 

 above values of k and the results placed against the actually observed quantities for each 

 station. The agreement between the observed and computed ranges is, in the main, quite 

 satisfactory. 



Magnbtic Disturbances 



As already stated, those days of observation on which particularly great disturbances in 

 magnetic declination occurred may be readily noted by reference to the tabulation of circle 

 readings of the magnet for the days on which the horizontal circle was shifted (see pages 20 to 26). 

 In view of the fact that no continuous observations were made either for magnetic inclination 

 or intensity in connection with those for declination, it has not been deemed worth while to 

 attempt any general discussion or comparison of these disburbances. As will be noted from 

 the miscellaneous remarks (pages 32 to 40), the magnetic storms were very frequently associ- 

 ated with the aurora borealis. On the other hand, the auroral displays were not always accom- 

 panied by magnetic disturbances, and vice versa. 



The observations of November i, 1903, between midnight and 8 A. m., local mean time 

 are of particular interest, as they cover the final portion of the great magnetic storm of October 



* A remarkable law, by L. A. Bauer. Journal of Terrestrial Magnetism. Volume II, p. 70. Cincinnati, 

 1897. Also United States magnetic declination tables and isogonic charts for 1902, by L. A. Bauer. U. S. De- 

 partment of Commerce and Labor, Coast and Geodetic Survey, O. H. Tittmann, Superintendent. 2d edition, 

 p. 51. Washington, 1903. 



