DEPARTMENT OF TERRESTRIAL MAGNETISM.* 



L. A. Bauer, Director. 

 GENERAL SUMMARY. 



The adverse cii'cumstances ensuing from the European war, which 

 have proved disastrous to several scientific enterprises of world-wide 

 character, have happily thus far necessitated only a curtailment of the 

 magnetic-survey work of the Department in certain land regions of 

 the globe. The ocean work, as will be seen later, has fortunately suf- 

 fered no suspension whatsoever. 



The chief region in which it was necessary to defer the sending of 

 additional magnetic expeditions was Central Africa. All necessary 

 arrangements had been successfully concluded, before the outbreak of 

 the war, for a second trans-Saharan expedition under the leadership of 

 an experienced magnetician, starting at Tripoli and proceeding to Lake 

 Chad, thence eastward to Egypt or southward to the Atlantic coast. 

 However, just as the expedition w^as about to start the war broke out, 

 and the countries which had promised the necessary official aid and 

 cooperation considered it best to advise a postponement of the project. 



Regarding future scientific aid from nations which have in the past 

 cooperated with the Institution in the execution of the world-tasks 

 assigned to the Department of Terrestrial Magnetism, letters received 

 from eminent investigators make it evident that, even after the ces- 

 sation of the war, less assistance can be given in the future, owing 

 chiefly to diminished financial resources. Thus there devolve upon us 

 increased reponsibilities if we are to secure a successful conduct of our 

 tasks. It is fortunate that our first general magnetic reconnaissance of 

 the Earth was so nearly completed before the war. 



The future magnetic-survey work, therefore, must consist in the 

 filling in of areas where additional data are needed, and assisting 

 certain countries in the completion of surveys undertaken by them 

 which the war conditions not only have interrupted but must indefi- 

 nitely postpone, unless outside aid is received. Furthermore, magnetic 

 observations must be repeated at a requisite number of points in order 

 to keep proper control of the changes ever going on in the Earth's 

 magnetism. 



But there is a second task of equal magnitude and importance to 

 that of the general magnetic survey of the globe, which implies the 

 mapping of the Earth's magnetic field and determining the Earth's 

 magnetic constants — one of fundamental importance in many investi- 

 gations relating to the physics of the Earth, namely, the study of the 



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