This collection includes miscellaneous letters and drafts of letters; genealogical notes, medical essays, copies of letters and essays sent to newspapers and magazines; bills and receipts; invitations; military and other commissions; and a biographical memoir of General John Lacey, 1823. There are also papers, principally official, of his son Lieut. B. S. B. Darlington, U.S.N.

Chiefly correspondence with Alexander John Gaspard Marcet on chemistry, with references to Sir Joseph Banks, Jean Francois Berger, Johan Jakob Berzelius, Jean-Baptiste Biot, and others; a few letters to and from John Bostock, Thomas Cooper, John Wilson Croker, Giovanni Fabbroni, and Henry Penneck.

These letters and papers include a memorandum book (1795-1827), lectures on botany and medicine, genealogical materials, committee reports from Columbia College, speeches, minutes of the New York Horticultural Society (1822-1828), letters to Sir James Edward Smith (1817-1826), a receipt book of Alexander Hosack (1781-1801), and diaries of Thomas K. Wharton (1830-1862).

Nine of these letters are addressed to Sir Alexander Dick of Edinburgh (1763-1768), and relate to Morgan's medical studies, his travels on the Continent, and the founding of the medical department of the College of Physicians. These are copies of originals in possession of Mrs. Dick Cunyngham, Prestonfield House, Edinburgh. In addition there are letters from Morgan to: Petrus Camper, William Smith, Samuel Vaughan, Jr.; and from Peter Collinson to Camper; Camper to Morgan; S. Vaughan Jr. to Camper; and an exchange between Christian F. Michaelis and Camper. These concern Morgan, with mentions of fossils (mastodon bones in America), natural history, comments on Franklin, Jefferson, and Angelica Kauffmann. These are from originals in the Petrus Camper Papers, on deposit (1976) at the University of Amsterdam Library.

This collection contains correspondence on natural history, expecially mollusks, fishes, and birds, and on medicine and social affairs, with references to the British Museum of Natural History. Also included are a paper by Owen on dinosaurs and a synopsis of a course of lectures, 1857.