DEPARTMENT OF TERRESTRIAL MAGNETISM. 



343 



in computing the tables is the same as that used in discussing the average 

 annual changes for the southern Atlantic. ^ The charts referred to are U. S. 

 H. 0. No. 2406 for 1920 and B. A. No. 2598 for 1917. 



^Units of fourth decimal C. G. S. 



*See Annual Report of the Director of the Department of Terrestrial Magnetism, Year Book 

 of the Carnegie Institution of Washington for the year 1920, pp. 310-312. 



