230 CARNEGIE INSTITUTION OF WASHINGTON. 



frequently assumed by those announcing the discovery of a new theory of 

 the origin of the Earth's magnetism. 



The continued studies of the Sun's magnetic field by the Mount Wilson 

 Observatory, combined with those of the magnetic fields of the Earth and 

 the atmosphere by the Department of Terrestrial Magnetism, are resulting 

 in a most interesting array of facts with regard to the magnetic fields of three 

 bodies differing greatly in their physical composition. All three bodies are 

 enveloped by magnetic fields showing some striking general characteristics 

 which seemingly indicate that the origin, strength, and orientation of the 

 magnetic field may be primarily dependent upon direction and speed of 

 rotation and upon size and mass of the rotating body. 



Of particular importance also to theories is the precise manner in which 

 the Earth's magnetism and its electricity are affected by variations in solar 

 activity and during solar eclipses; accordingly extensive studies have been 

 made in these directions. Respecting possible eclipse effects, it is noted that 

 the Department's expedition to Point Loma, California, reported that, during 

 the solar eclipse of September 10, 1923, appreciable magnetic and electric 

 effects confirming previous results were obtained. 



Enough has been said to indicate, in a general way, the trend of our inves- 

 tigational work in the field and in the laboratory. Fuller statements will 

 be found under their appropriate headings. 



COOPERATIVE WORK. 



The work done by the Department of Terrestrial Magnetism in cooperation 

 with governmental and other institutions and with individual investigators 

 is extensive and varied. Besides the interchange of magnetic and electric 

 data with hydrographic bureaus, observatories, and magnetic services the 

 world over, the Department has cooperated with the following organizations: 

 the United States Coast and Geodetic Survey, the United States Hydrographic 

 Office, the United States Bureau of Standards (especially in radio investi- 

 gations), the United States Weather Bureau, the Dominion Observatory 

 and the Meteorological and Magnetic Service of Canada, the British Ad- 

 miralty (Greenwich Observatory), the Amundsen Arctic expedition, the 

 MacMillan North Greenland expedition, Liberian Boundary Survey, Ber- 

 muda Hydrographic Survey, Department of External Affairs of New Zealand 

 in the maintenance of the Apia Observatory in Western Samoa, Common- 

 wealth Weather Bureau and Department of Agriculture of Western Australia, 

 University of Western Australia, Postal and Telegraph Offices of Australia 

 respecting information as to magnetic storms and earth currents. Section of 

 Terrestrial Magnetism and Electricity of the International Geodetic and 

 Geophysical Union, Commission on Terrestrial Magnetism and Atmospheric 

 Electricity of the International Meteorological Committee, National Acad- 

 emy of Sciences, National Research Council, and American Geophysical 

 Union. 



Special reference may be made to the cooperative work with the Institu- 

 tion's archaeological expedition to Guatemala under the general charge of 

 Dr. Sylvanus G. Morley. Observer W. A. Love was assigned to the party 

 under O. G. Ricketson, in order to determine the geographic positions and 

 orientations (astronomic and magnetic) of the archaeological ruins investi- 

 gated (see abstract, pp. 261-262). 



