Correspondence, 1895-1957, including letters sent by Langmuir to his mother while he was a student at the University of Gt̲tingen in 1906; letters from fellow scientists such as Niels Bohr, Vannevar Bush, and Willis R. Whitney; correspondence with Leopold Stokowski concerning improvements in sound reproduction. Experimental notebooks, 1894-1957, containing data which led to the development of the gas-filled incandescent lamp, the high vacuum power tube, atomic hydrogen welding, and screening smoke generators for the Armed Forces; the notebooks are supplemented by extensive subject files. Included in these files are a group of charts of Lake George, NY, and also material on cloud seeding experiments and smoked bathythermograph records obtained at Lake George. The collection also contains speeches and articles by Langmuir, many in manuscript form. There is a small group of published scientific journals annotated by Langmuir, as well as newspaper clippings, a card reference file, photographs, and awards.