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.

The primary correspondence (ca. 65 letters) is with William Cooper (1798-1864) on Bonaparte's publications, especially "American Ornithology" and "Observations on the Nomenclature of Wilson's Ornithology," but also included are many references to American and European men of science and learned societies. There are also letters to Isidore Geoffroy Saint-Hilaire, George Robert Gray, Titian Ramsay Peale, and Wilhelm P. S. Rüppell.