The collection consists of Xerox copies of works and correspondence by William Cowper collected by Ryskamp, as well as correspondence, notebooks, and miscellaneous material of Neilson Campbell Hannay, a Cowper scholar and collector. There are copies of Cowper's works at the Huntington, Yale University, and Bodleian Libraries, letters at Princeton (1783-1799), including some in the Hannay Collection, and letters not at Princeton (1790-1799). The collection contains original correspondence (1925-1961) between Hannay and Cowper scholars, collectors, and manuscripts dealers, including M. King Martyn, Catharine Barham Johnson, and Kenneth Povey. There are four notebooks kept by Hannay listing autograph letters by Cowper in Hannay's possession, miscellaneous data relating to Cowper and his circle, a list of negatives of Cowper material, a bibliography, and Xeroxes of miscellaneous research material. Also included are photographs of Cowper's portraits, family, and friends, and topographical photographs relating to Cowper. In addition, there are negative plates of Hannay's Cowperiana, printed matter such as Sotheby's catalogues, and newspaper clippings.

An addition to the collection consists of one bound volume of material compiled by Frances Jane Monckton: containing nine letters and eight poems, 1815-1820, written by the English poet William Hayley (1745-1820) and sent to Frances Jane Monckton and occasionally her sister Eliza; one undated poem, "Beau's Reply" in the hand of William Cowper; and one poem, 1852, by Monckton on the presentation of the volume to her nephew, Richard Monckton Milnes (1809-1885). A box of additional copies of Cowper letters and manuscripts, as well as original correspondence of Thomas (founder of the Cowper Museum) and Angelina Wright, is included.