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.

This collection contains minutes of the Society, 1781-1975; minutes of the directors of the Corporation, 1929-1947; membership book (with signatures of early members), 1785; and names of later members. There are also deeds to the meeting house and burying ground; treasurers' accounts; reports of officers and committees; bills and receipts for constructing, maintaining, and repairing the meeting house; cancelled checks; and letters to the Society and its officers, especially Samuel Wetherill, 1883-1884.