Joseph Henry's Letter to Alexander Dallas Bache (August 18, 1865), August 18, 1865, Smithsonian Archives - History Div, Letter from Joseph Henry, first Secretary of the Smithsonian Institution, to his close friend Alexander Dallas Bache, a physicist and Smithsonian Institution Regent, August 18, 1865. In the letter, Henry describes events at the Smithsonian, including repairs being made to the Smithsonian Institution Building, or "Castle," following the fire that occurred on January 24, 1865..