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Volume VI, the last volume of the comprehensive work on Aerodynamic Theory prepared under a grant of the Guggenheim Fund for the Promotion of Aeronautics, is sub‐divided into five divisions (P‐T). Division (P), by Professor Durand, deals with the aeroplane as a complex of four interacting systems—the lifting system, the non‐lifting system, the propulsive system and the control system. These four systems interact mutually, and the purpose of the division is to give in a descriptive and non‐mathematical way a general discussion on the nature of these interactions, reference being made where necessary to the more detailed mathematical treatments given in earlier divisions.