These manuscripts complement the family archives of the Willughbys, Barons Middleton of Wollaton Hall, and particularly to Francis Willughby (1635-72) and John Ray (1627-1705). These letters appear to have been lent by Francis Willughby's daughter to William Derham, but not returned to the family archive. Extracts were published by Derham in "Philosophical letters between the late learned Mr Ray and several of his ingenious correspondents", 1718.