Correspondence, writings, lectures, subject files, biographical information, printed materials, photographs, and other materials relating to Eckart's career as oceanographer and physicist. Pertains to Eckart's research in physics especially quantum theory and in thermodynamics while on the faculty of the University of Chicago (1928-1946); resignation from the U. S. Office of Scientific Research and Development's National Defense Research Committee in opposition to development of the atomic bomb (1941); work on the underwater detection of submarines at the University of California's War Research Division during World War II; and contributions to oceanography as director of the Marine Physical Laboratory (1946-1952) and professor of geophysics at Scripps Institution of Oceanography (1946-1971). Also includes material relating to Eckart's views on the origin and development of exact sciences; participation in professional organizations expecially the U. S. National Academy of Sciences's Committee on Science and Public Policy; service in the advisory group, Institute for Defense Analyses (1967-1968); work as a reviewer for scientific journals, member of the Editorial Advisory Board for the Johns Hopkins University Applied Physics Laboratory series in applied mathematics and mechanics; and consultant for commercial firms, including General Dynamics Corporation and Rand Corporation. Included also are materials documenting Eckart's contribution to the posthumous publication of John Von Neumann's works, and calculations (1926-1927) of Hendrick A. Lorentz, in which he used some of Eckart's equations. Correspondents include P.A. M. Dirac, Werner Heisenberg, Robert Andrews Millikan, J. Robert Oppenheimer, Wolfgang Pauli, Erwin Schrd̲inger, Arnold Sommerfeld, and Eugene Paul Wigner.