This typed autobiography, covering the period from Barus' birth to 1930, includes reports concerning the United States Geological Survey, the United States Weather Bureau, and Barus' work in cloud condensation.

These papers contain seven letters to his wife (1808-1833), a fragment of autobiography on his painting and studies, a notebook containing copies of correspondence about his portrait of Washington, John Godman's Ode suggested by Rembrandt Peale's National Portrait of Washington (1824), and a commonplace book containing kitchen and medicinal recipes.

These papers include letters, reports, and journals relating to Indians, Moravian missions, and communities at Salem (N.C.), Bethlehem (Pa.), and Gnadenhütten, Muskingum, and Fairfield in Upper Canada. Also included are personal correspondence and an autobiography. Contains 86 letters, journals, reports, etc., pertaining to the travels and missionary activities of Heckewelder, mostly in German. 7 journals, memoranda, and miscellaneous materials of David Zeisberger, pertaining to his years with Indians. Many of the former materials were utilized and published by Paul A. W. Wallace (1958); the latter includes Zeisberger's Memoranda on Indians; Journey to the Six Nations, Nanticokes and Shawanees in April, 1752, to July, 1752; Conrad Weiser, Observations made on the pamphlet entitled "An enquiry ... [1759]"; Birth records for the 1780's at Friedenshutten and Gnadenhütten; Catalogue of Indians baptized by the United Brethren, 1765-1814 (721 names); and a memorandum of Zeisberger on the Onondaga.

This collection was assembled by Court and was partly used in the book, "The History of the Microscope" (with Reginald S. Clay, London, 1932). There is historical correspondence (including some by Court), documents, broadsides, and photographs, concerning microscopes and instruments. This includes material on Joseph Bonomi, James Epps, John Lee, Edward Nairne, and others. There is significant material on Cornelius Varley: account book, autobiographical sketch, watercolors and sketches, etc. This collection also contains a large number of deeds pertaining to the property of John Lee (1783-1866), Fellow of the Royal Society and an amateur astronomer. In addition, there are about 300 pamphlets, including early trade and auction catalogs, used by Court for his research.

The manuscripts of father William Mitchell and daughter Maria Mitchell are not easily separated, and are treated here together. The collection includes William Mitchell's autobiography, his memoir of Judge Walter Folger of Nantucket, astronomical and meteorological observations, lectures, family and other correspondence.