MAGNETIC OBSERVATIONS 



303 



31 to November i, 1903.* The extreme values of declination observed at Teplitz Bay during 

 this period were 37 31' E at 4:01 A. M. and 20 13' E at 5:49 A. M., local mean time, the 

 greatest range thus being 17 18' in 1.8 hour. During the same absolute period the records 

 of the Cheltenham Magnetic Observatory of the United States Coast and Geodetic Survey show 

 an extreme range of 32 , while the maximum range for the entire storm at this point was about 

 three times as much, viz., 97. i. From this comparison it appears highly probable that during 

 the maximum violence of this disturbance on October 31, 1903, the extreme range in magnetic 

 declination at Teplitz Bay may have been as much as 52. 



The highest value observed during the entire series was 37 31' E, as above, on November 

 i, 1903 ; the lowest, 19 51' at 8:27 p. M. on June 15, 1904. The absolute observed range was, 

 therefore, 17 40'. The unusual character and magnitude of the disturbance of October 31, 

 1903, is thus at once apparent. 



SECULAR CHANGS IN MAGNETIC DECLINATION 



The only previous observations of the declination of the magnetic needle at Teplitz Bay 

 available for use in determining the secular change in this element are those made by Com- 

 mander Cagni, of the Italian Expedition of 1899 and 1900. His observations as reported by 

 Professor Palazzo f have been corrected for diurnal variation as determined from the preceding 

 discussion. The following table gives a synopsis of these determinations so reduced (the cor- 

 rections on account of diurnal variation are the mean values over the respective periods of 

 observation) : 



The resulting mean values of 21 15/6 and 21 25/0 correspond to mean of day for the 

 epochs 1899.66 and 1900.55 respectively. 



Unfortunately the multitudinous duties of the various members of the Ziegler Expedition 

 field force prohibited making observations at the Italian station until just shortly prior to the 



* Journal of Terrestrial Magnetism and Atmospheric Electricity, volume IX, 1904, pp. 25-33 ', also An- 

 nalen der Hydrographie und maritimen Meteorologie, 1904, Heft III, pp. 112-127. 



t Osservazioni scientifiche esequite durante la spedizione Polare di S. A. R. Luigi Amedeo di Savoia, Duca 

 degli Abruzzi. Milan, 1903. Pp. 453-462. (Relazione sulle osservazioni magnetiche fatta dal Professore 

 Luigi Palazzo.) 



