This collection consists principally of correspondence with Alexander Dallas Bache, Louis Agassiz, Joseph Henry, and Titian Ramsay Peale on general scientific topics, although personal and family matters were discussed with Bache. Topics discussed in the letters include the University of Pennsylvainia, boiler explosions, education, the National Academy of Sciences, the Smithsonian Institution, fossils, magnetism, solar eclipses, the American Philosophical Society, weights and measures, the U.S. Coast and Geodetic Survey, scientific instruments, American Civil War, electricity, the United States Mint, the Franklin Institute, scientists of the period, natural history, and publications.