This fonds contains materials primarily related to Moss's work on the soil survey of Saskatchewan, and academic work connected to soil classification and land use.

This collection contains considerable material relating to aviation history, particularly in western and northern Canada, including material on: the Keng Wah Aviation School for Nationalist Chinese pilots; the RCAF; illustrations of the technology of flight; reference material; and microfilms of the Hudson Strait Expedition fonds (1927-1928) and "The Bulletin" (Western Canada Airways, 1929-1937). Additionally, there is material on Tweddell's other research interests, notably aerial mapping and surveying.