Carnegie Institution of Washington. Dept. of Terrestrial Magnetism, Herbert W. Graham, William Albert Setchell, Aaron L. Treadwell, W. M. Tattersall, James O. Maloney, Harry G. Barber, Alexander Wetmore, M. W. de Laubenfels, Austin H. Clark, E. A. Chapin, Hoyt S. Hopkins, Doris M. Cochran · First published 1943