Table 737 rgj 



MEAN ANNUAL VALUES OF MAGNETIC ELEMENTS AT OBSERVATORIES 



In order to show the change of the annual rates of secular variation with geographical 

 position and with time and the accelerations in those rates without unduly extending the 

 tables, the values of the elements have been given for each fifth year beginning with 1900, 

 and for consecutive years from 1925 or 1930. When the observatory was established sub- 

 sequent to 1900, values obtained during the first year of the operation are given. 



The lack of uniformity in the distribution of magnetic observatories should be taken into 

 account. The satisfactory computation of the so-called magnetic constants of the earth, the 

 investigation of the laws of secular variation and daily variation, the study of the manner 

 of propagation of magnetic storms and their relation to other world-wide phenomena, require 

 additional observatories in the southern hemisphere, specifically in Africa, and on favorably 

 located islands in the southern Pacific and Atlantic oceans. 



"See also tables for previous and intermediate years in Terr. Mag., 4, 135; 5, 128; 8. 7; 12. 175; 16. 209; 

 20 131; 22, 169; 23, 191; 25. 179; 26, 147; 27, 157; 29. 149:31, 27; 32, 27; 33. 95; and 35. 165. Unless otherwise 

 Indicated values are from continuous magnetograph records. Preliminary values, pending final reductions, are 

 Indicated by parentheses. Observatories marked by an asterisk (*) are in regions of local disturbance. b Values 

 from absolute observations only. ' No observations in February and March. J Absolute observations during 

 June and July only. 



Smithsonian Tables 



