Letters about a proposed Brazilian expedition, geology, zoology, and related subjects from Joel Asaph Allen, James Dwight Dana, Arnold Henry Guyot, James Hall, Thomas Sterry Hunt, Alpheus Hyatt, Alpheus Spring Packard, Samuel Hubbard Scudder, Addison Emery Verrill, Jeffries Wyman, and other scientists; also notification of Hartt's membership in the Boston Society of Natural History, his US citizenship papers, and other documents.