The article on “Differentials”, in the May Gazette —based on a discussion at the last Annual Meeting of the Association, and referring back to articles of July 1931 and February 1932 —has so clarified certain issues for the writer as to confirm a long-standing conviction that the standard definition of “differentials” is quite unsound, and that the view set out below (which he had developed in his own teaching ) is much truer to all the facts of the situation.