This collection contains correspondence, reports, notes, and notebooks. Clarke's participation in various organizations is documented, including the American Philosophical Society, American Chemical Society, American Otological Society, and the American Society of Biological Chemists. His chemistry research is detailed in thirteen notebooks, 1903-1971 (the 1903 volume is on photographic chemistry and processes). There is also one volume on the clarinet, for Clarke was an expert clarinetist. The personal and family correspondence is principally with Mrs. Dorothy Clarke Middleton and Mrs. Agnes Helfreich Clarke.