These letters of American Philosophical Society members and prominent early American scientists were selected from Carson's extra-illustrated draft of "A History of the Medical Department of the University of Pennsylvania" (Philadelphia, 1869).

These papers include diaries (1777-1782), expense books (1794-1804), notebooks, a commonplace book, drafts of essays, excerpts from minutes of Friends' Monthly Meeting, Tortola (1741-1761), newspaper clippings, sketches, and correspondence. Also included are letters and papers of Mrs. Thornton.