Letter, 9 December 1870
Letter, 27 April 1870
Letter, 17 October 1870
Letter, 28 November 1870
Letter, 20 December 1870
Letter, 15 April 1871
Letter, 4 July 1871
Letter, 9 December 1871
Letter from H. G. Vennor to B.J. Harrington regarding the Geological Survey of Canada.
Letter from George J. Brush of the Sheffield Scientific School of Yale College.