Correspondence, writings, financial papers, newspaper clippings, printed matter, maps, tables, charts, photographs, and other papers relating chiefly to Rotch's interest in aeronautics and meteorology. Subjects include atmospheric experiments and observations, the air flight trials of the Wright Brothers, and the International Aeronautical Congress at the Louisiana Purchase Exposition in 1904 in St. Louis, Missouri. Correspondents include Cleveland Abbe, James Allen, Louis P. Casella, Octave Chanute, Glenn Hammond Curtiss, Oliver L. Fassig, A. Hildebrandt, S.P. Langley, Percival Lowell, Alexander McAdie, James Means, Hermann W.L. Moedebeck, Edward C. Pickering, Charles Stewart Rolls, Sir Napier Shaw, Léon Philippe Teisserenc de Bort, Robert DeCourcy Ward, Orville Wright, and Wilbur Wright.