Photostatic Copies of Letters on Cement Production Contains a declaration signed by J B S Haldane and the Commissioner for Oaths that the enclosed letters of Sir William Firth which Haldane received from H R Ayton are true copies; a cover note; two letters from Sir William Firth to H R Ayton of Richard Thomas & Co.; and three letters from M Stewart, Chairman of Associated Portland Cement Manufacturers and Commissioner for the Special Areas, to Sir William Firth. The letters are about the production of cement from Blast Furnace Slag, and Firth's attempts to persuade Stewart to co-operate in this method of production. 1941