SOLAR ACTIVITY AND TERRESTRIAL MAGNETIC 

 DISTURBANCES. 



By L. a. BAUER, 



Director of Department of Research in Terrestrial Magnetism, Carnegie 

 Institution of Washington. 



{Read April 23. 19 10.) 



It has already been my privilege to lay before this society, on 

 various occasions, some of the results obtained since 1905 of the 

 magnetic survey work, chiefly of the oceans, conducted under the 

 auspices of the Carnegie Institution of Washington. At the present 

 rate of progress it seems reasonable to suppose that by the year 191 5 

 it will be possible to construct a new set of magnetic charts as based 

 upon homogeneous data largely obtained by one organization. 

 Along with the magnetic survey of the oceans, begun on the 

 " Galilee " in the Pacific Ocean in" 1905 and continued until May, 

 1908, and now being conducted on the " Carnegie " in the Atlantic 

 Ocean and later to be extended to the Indian Ocean, that of land 

 areas is likewise in good progress, parties of the Carnegie Institution 

 of Washington having already made notable expeditions in magnet- 

 ically unexplored regions in all parts of the globe. 



Provision has thus been made for a rapid and continuous accumu- 

 lation of the data required for mapping the so-called " permanent " 

 magnetic forces of the earth. As a matter of fact, however, the 

 earth's magnetism is subject to continuous change, and owing to the 

 so-called secular changes but a few years — five to ten — suffice to 

 completely alter a chart showing the direction of the compass at 

 various points over the globe. Hence, the work as being executed 

 likewise embraces the determination of the secular changes in the 

 earth's magnetism at a sufiicient number of stations to permit apply- 

 ing the necessary corrections for keeping magnetic charts up to date. 



However, there is another side to magnetic work, certainly not 



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