The Montreal Mendelssohn Choir donated eight volumes of choral sheet music from the Choir’s library in 1895, a year after the Choir’s dissolution. There are only seven extant volumes in the collection because volume 6 has been missing since at least the 1980s.

Three volumes of choral sheet music from the Choir’s library were donated to McGill University by the Estate of D. Torrance Fraser, a former choir member, in 1926. The pieces in these three volumes are second copies of those pieces found in Series 1. In 1927, another volume of sheet music from the Choir’s library was donated to McGill University by the Estate of D. Torrance Fraser. This fourth volume (DTF2) contains many pieces not found in the other volumes.

Anna Dawson Harrington's papers consist chiefly of incoming correspondence, including: 1.5 cm of letters from J. W. Dawson, 1868-1896; 3 cm from Margaret Mercer Dawson, 1870-1902; 10 cm from George Mercer Dawson, 1865-1901; 7 items from William Bell Dawson, 1868-1876; 5 items from Rankine Dawson, 1871-1899; 15 items from Eva Dawson Atkin, 1880-1896; 13 cm from her husband B. J. Harrington, 1876-1906; 2 cm from her children, 1892-1913; 1 cm of congratulatory letters at the time of her marriage, 1875-1876; 13 letters from friends and associates, 1867-1911; 4 cm of letters of sympathy on the death of her husband, 1907; 2 cm of letters concerning subscriptions for his portrait, a girlhood diary, 1866-1871 and some notes for biographies of J. W. Dawson and George Mercer Dawson. Earlier years contain substantial correspondence from her brother George during his education in London and early travels with the International Border Survey and then the Geological Survey of Canada. Substantial family correspondence with her children during their youth and her husband Bernard relates to domestic matters, such as the household, new house, the children's health and activities, with frequent passing mention of finances.

The administrative records series contains documents that reflect the structure and mandate of the Society, such as their constitution, acts, by-laws, yearly agenda, bookings, and membership lists. Summaries of meetings provide information of the NHSM’s interactions with other societies, notably the Horticultural Society, and also includes correspondence with society members, lists of addresses. An obituary of Society Librarian Charles Robb and an example of a membership certificate belonging to J. H. Joseph may also be found.

Series consists of three scrapbooks. The scrapbooks contain notes, patient prescription information, reprints of various publications by MacDonnell, and lots of news clippings concerning various topics such as the history of Montreal, McGill University, the McGill faculty, Montreal General Hospital, and obituary notices

The series consists of correspondence to William Bell Dawson from George Mercer Dawson, between 1865 and 1899; John William Dawson, 1865; Margaret Mercer Dawson, 1868, 1871; Department of Interior Canada, 1923; Rankine Dawson, undated; one receipt of a 14-month subscription to Leisure House; Psalm of the Honest Investor; three photographs of Florence Jane Elliott Dawson and William Bell Dawson; seven photocopies of printed lectures on evolution; two of his daily journals, 1907 and 1909; and his letters written to the Redpath Museum, 1921.

The series consists of a cutting of Robert Abraham’s obituary, taken from the Montreal Transcript.

This series contains ephemera created by McGill University, McGill-affiliated student groups, and local organizations between 1855 and 2018. Also includes commercially-produced material whose subject is McGill.

This series is described at the file level. Includes flyers, programmes, brochures and pamphlets, postcards, invitations, tickets, posters, membership cards, greeting cards, dance cards, and other materials.

This series contains book lists and catalogs which document Mappin’s personal antiquarian book collection. Also includes files about Canadian authors’ deposits and archival fonds at Library and Archives Canada. Includes professional correspondence with other antiquarian books sellers, and documents the contents of their personal or donated collections. Contains machine typed personal index cards containing entries for authors, events, printings, etc. File #1210.02.06.05 contains the cover for The Goblin : a Brief History of Canada's Humour Magazine of the 1920s written by John Mappin and Carl Spadoni however the contents are missing.