Letter, 13 January 1876
Letter, 13 May 1878
Letter, 29 January 1880
Advertising postcard from F. Kaldenberg Co. to B.J. Harrington offering specimens of amber with antedeluvian insects.
Letter, 28 May 1889
Letter, 19 June 1890
Letter, 28 March 1895
Letter, 22 June 1897
Letter, 11 April 1898
Letter, 2 March 1906