Unpublished French translation of the second part of Hales's book on the ventilator. Possibly in the hand of Pierre Demours who translated and published the first part of the book as 'Description du Ventilateur' in 1744. Bears a few editorial notes and alterations in another hand. Accompanied by what appears to be part of an envelope bearing 'Monsieur DuHamel de Monceau à Paris' and a note, probably in his hand, that the manuscript was written somewhat out of order, but contains quelque chose de bon” or “something good”.