Correspondence, diaries, notes on the life of Simon Henry Gage; notebooks on lectures at Ithaca High School and Cornell University; printed matter on physics and related subjects; slides, photos, photographic plates, and miscellaneous papers. Includes correspondence and other papers pertaining to Henry Phelps Gage's work as head of the Optical Laboratory of Corning Glass Works (1911-1947) and to his membership in various scientific societies; also personal and family correspondence, including papers of Susanna Phelps Gage.