Consists of Hess's papers, articles, reports, lecture notes, on-site field notes, notebooks, correspondence, committee materials, off-prints, unpublished papers, photographs, documents, seismological charts, slides, and printed matter, as well as some papers of others. The professional correspondence includes letters from colleagues in academe, the U.S. government, geological organizations, and scientific societies. Much of the material in the collection covers the varied scientific topics with which Hess was engaged-in particular, Hess's work with the National Academy of Sciences' Space Science Board, which advises the National Aeronautics and Space Administration on scientific matters. Hess participated in the academy-sponsored Mohole Project, which had the objective of drilling a hole through "Moho," the Mohorovicic seismic discontinuity separating the mantle of the earth from its crust. The collection also contains work Hess did for the Office of Naval Research of the Navy Department, including material relating to his theory of continental drift. Furthermore, there are materials pertaining to the Princeton Caribbean Research Project, organized and directed by Hess, which explored every aspect of Caribbean geology.