Letter to John A. Mullin, October 3, 1889
Letter to Daniel Coit Gilman, March 6, 1890
Letter to Henry Vining Ogden, November 10, 1890
Letter to Richard (Dick) MacDonnell, December 9, 1890
Letter to John H. Musser, March 26(?), 1890
Letter to Henry Vining Ogden, April 1890
Letter to Edward A. Sharpey Schäfer, April, 17, 1890
Letter to Henry Vining Ogden, September 8, 1890
Letter to Walter Baumgarten, October 3, 1890
Letter to Joseph Leidy, November 29, 1890