4 Land Magnetic Observations, 1914-20 



With the completion of Volumes IV and V, it is possible to undertake the 

 reduction of the accumulated magnetic data since 1905 to a common date for the 

 construction of new world magnetic charts, and to make a new analysis of the 

 Earth's magnetic field on the basis of more complete and more accurate data 

 than heretofore available. But for the Great War, these objects of our magnetic- 

 survey work would have been realized earlier. 



The Director of the Department (L. A. Bauer) and the Chief of the Magnetic 

 Survey Division (J. A. Fleming) desire to express their sincere appreciation and 

 deep sense of obligation to those, especially to the observers and computers, whose 

 devotion and unflagging interest have made possible the accumulation of the mass 

 of scientific data presented in this volume. 



One of the main objects to which the Department of Terrestrial Magnetism 

 has devoted its energies since it was established in 1904 the general magnetic 

 survey of the globe has now been completed for the major part of the Earth. 

 While this task has been accomplished chiefly through the labors of the Depart- 

 ment, very notable contributions have been made by various countries, either 

 through repetition of former magnetic surveys, or through new surveys. The 

 work of the Department has been confined, in the main, to the oceans and to those 

 countries or regions where, for one reason or another, magnetic data would not 

 otherwise be obtained immediately. In some regions required magnetic surveys 

 were accomplished by cooperation with existing organizations, or with interested 

 investigators. The Department furthermore cooperated successfully with the 

 Peary Arctic expedition, the Mawson Antarctic expedition, and the Amundsen 

 Arctic expedition, now in progress; in this manner valuable data in polar regions 

 were obtained. It is a pleasure to acknowledge the cordial and valuable aid 

 received from magnetic institutions generally, as well as from government officials 

 and diplomatic representatives of the countries visited; this aid has in no small 

 measure contributed to the achievement of the desired object. 



The land observers of the Department have performed their assigned duties 

 in every major political subdivision of Africa, except British and Italian Somali- 

 land; in every country of Asia, excepting Afghanistan, the Himalayan states, and 

 Chosen, but including every province of China except Tibet; in every state of 

 Australia; in New Zealand; in 11 European countries; in every country of North 

 America; in Greenland and Iceland; in every country of South America; in the 

 principal islands of the Atlantic and Indian Oceans; and in 25 of the principal 

 groups and isolated islands of the Pacific Ocean. 



The enumeration of stations has been made on the following basis: At base 

 stations and at observatories where instruments are intercompared, every point at 

 which observations are made is counted as a separate station; the same procedure 

 has been followed with regard to locally disturbed areas where it is generally 

 necessary to make observations at several points; reoccupied stations (repeat sta- 

 tions) are invariably counted as but one station, though it may happen at times 

 that the reoccupied station is not quite the same as the original one. The enu- 

 meration of expeditions has been made in accordance with the time consumed, 

 the general region traversed, and the character of the work performed. 



