Correspondence; travel notes; diaries; photograph albums; postcards. The correspondence (bulk dates, 1903-1905, 1933-1942, 1950-1954) consists of Williams' observations to his parents and later to his children on the various phases of his career, including his years (1903-1905) as a student at the Universitt̃ Berlin, where he became acquainted with Max Planck and Max von Laue; his year at the Cavendish Laboratory at Cambridge University (1928-1929), and his years at Amherst College (1910-1947) including his involvement in the establishment of the Snell Museum of Physics at Amherst (1932-1933); and his experiences at General Motors (1949-1950) studying magnetism; correspondence with Robert M. Hutchins and Walter G. Cady (1945-1953). The travel notes and diaries written in Europe (1903-1905) are supplemented by photograph albums and postcards.