MAGNETIC OBSERVATIONS 



Inasmuch as Commander Cagni's observations were, with but one exception, made during 

 afternoon hours, his values have also been reduced approximately to mean of day by the same 

 diurnal variation curve (the corrections given are mean values over periods of observation). 

 These results are as follows, the observed quantities being taken from Professor Palazzo's 

 discussion :* 





The resulting mean values of 68057 and 6823?- correspond to mean of day for the epochs 

 1899.66 and 1900.55 respectively. From these the magnetic horizontal intensity at the Italian 

 station forthe epoch 1900.10136814^. Referred to the Ziegler Expedition station, this becomes 

 68147 687 = 67467. At the latter location the value derived was 6768 7 for the epoch 1904.16. 

 Hence the horizontal intensity of the earth's magnetic field has, in the region of Teplitz Bay, 

 in a period of four years increased 22 7 (0.00022 C. G. S.). Hence, assuming a linear change 

 during the elapsed interval, the rate of change in magnetic horizontal intensity due to secular 

 variation is 



+ 67 (0.00006 C G. S.) per year. 



This rate of increase confirms that adopted by Professor Palazzo in his discussion above 

 referred to, namely, +97. At the stations Mossel Bay (y = 79 53' N ; A= 16 04' E) and 



Cape Thordsen (<f = 78 28' N ; A = 15 42' E) for the periods 1873.5 to 1899.7 

 1899.7 D r - Solanderf has deduced the annual rates 10 7 and 37 respectively. 



1883.2 to 



*Osservazioni scieatifiche esequite durante la spedizione Polaredi S. A. R. Luigi Amedeodi Savoia, Duca 

 degli Abruzzi, 1899-1900. Milan, 1903. Pp. 475-500. (Relazione sulle osservazioni magnetiche fatta dal 

 Professore Luigi Palazzo.) 



fSee reference, page 305. 



