These are copies of letters, chiefly relating to the American Philosophical Society, from Peter S. Du Ponceau, John Vaughan, and James Mease. There are a few original letters, one to Benjamin Franklin Peale.

These papers include correspondence, legal documents, financial records, family material, maps and plats, pictures, printed materials, diaires, and journals of geological expeditions. Also included are undated materials.

These are letters written from America, to Murchison, discussing geology, natural history, and contemporary topics.

The collection of about 850 items covers the period from 1782 to c. 1936, with the bulk dating to the 1780s to 1840s. The collection is divided into four series. Series I contains correspondence relating to a wide variety of topics, including French and English politics, business, trade, religious matters, and personal affairs. Many of the items are letters of introduction. There is also information on John Vaughan's immigration to America, Joseph Priestley, vaccines and inoculation (with Jefferson's comments on the same), Vaughan's business in Philadelphia, and the American Philosophical Society. Also included in this series are 2 boxes with copies of Vaughan correspondence as well as miscellaneous notes by E. W. Madeira, gathered in the course of his research on Vaughan in the 1930s. Series II consists of three volumes. Included are two of Vaughan's commonplace books. One, entitled, "J. Vaughan's book," May 17, 1779 (47 pp., in Latin; 870/L34), includes mostly Latin notations. The other commonplace book, dated 1783 (ca. 66 pp.; B V 462.c), includes comments on several prominent Americans, such as Benjamin Rush and David Rittenhouse, as well as American society generally. The third volume is a copybook with thirty letters spanning the period 1784 to 1801 (B V462.1). Series III includes material relating to Vaughan's administration of the estate of the Philadelphia merchant Samuel Merrick, 1796-1822 (Vaughan-Merrick Papers, B V462.m; 2 boxes). Series IV consists of correspondence between Vaughan and the DuPont Co. for which he served as agent (B V462.4; photocopies of 73 letters).

Mentioned in these letters are personal affairs, experiments, Babbage's calculating machine, and his "Bridgewater Treatise," second edition.

These papers reflect Isaac Hays' interests and activities in the medical profession and as an editor. His interest in paleontology, especially in the controversy with G. W. Featherstonhaugh, is also represented. There is one separate volume (77 letters) containing correspondence about natural history and naturalists, written to Hays by C. L. Bonaparte, George Ord, Thomas Say, and Charles A. Lesueur. The correspondence in the larger collection, however, contains much material on the American Journal of the Medical Sciences, particularly illuminated in the correspondence with John D. Godman. The I. Minis Hays material consists of letters from doctors, relating to medicine and medical publications and editing, as well as medical organizations. Most significant of the correspondence is that with John Shaw Billings (ca. 60 letters).