Collection includes administrative files, professional correspondence, course lectures and related materials, research and project files, reprints by Mason and others, and miscellaneous files. For each course taught by Mason all materials were combined into a course book which included the syllabus, problems, examinations, lecture notes, and grade books; for courses such as thermodynamics and kinetic theory, which Mason taught over many years, these course books provide insight into change and continuity in Mason's teaching. Professional correspondence includes letters to colleagues, recommendations, and material relating to conferences and meetings. Mason's research files include folders for each work in progress, proposals/grants/calculations, and published papers (containing a copy of the published reprint, edited drafts, supporting data and calculations, and, in many cases, correspondence with editors collaborators, and readers).