The principal manuscript in the David Hume Collection is the bound volume containing letters from David Hume to the Comtesse de Boufflers. There are also letters from Jean-Jacques Rousseau and others for a total of 59 letters. This volume was acquired 28 November 1950 at the sale of the library of Lucius Wilmerding at the Parke Bernet Galleries in New York City. This collection of letters was the basis for the anonymously edited Private Correspondence of David Hume with Several Distinguished Persons, Between the Years 1761 and 1776. Now First Published From the Originals. (London: Printed for Henry Colburn and Co., 1820.) One of the McGill copies of this book belonged to the Montreal lawyer and book collector Frederick Griffin (1798-1877). For a description of this volume of manuscript letters, see: Raymond Klibansky, "Hidden Treasures at McGill", Fontanus vol. II (1989), 79-82. In addition to this volume there are eight other Hume letters. Some of these have been published by Professor Klibansky and Ernest C. Mosser in New Letters of David Hume. (Oxford: Clarendon Press, 1954).
Interestingly, the Montreal book collector Gerald E. Hart (1849-1936) had in his library an unrecorded and apparently untraced David Hume letter. This letter is dated Edinburgh 1757 and reads in part:
(See: Catalogue of the library, manuscripts, autograph letters, maps and prints forming the collection of Gerald E. Hart, Esq., of Montreal :... comprising rare Americana, scarce black letter books, illuminated MSS., rare French belles lettres ... books from provenances illustres and bound by master binders, early Canadian imprints ... autograph letters of the sovereigns of France and England ... (Boston: C.F. Libbie, Jr., printer,1890), item 2769 (p. 269). The context of this letter seems to be letter 133 in The Letters of David Hume edited by J.Y.T. Greig (Oxford: Clarendon Press, 1932).
Finally, there are photographic copies of Hume manuscripts
held by the Royal Society of Edinburgh and typed copies of official letters
on Canada from the manuscripts of Sir Mark Dalrymple.