Jevons, Jenkin, and Walras on demand-and-supply analysis in the theory of exchange

In his economic writings Jevons insists on the allegedly fundamental role played by the so-called "laws of supply and demand" in his theory of exchange; yet no demand-and-supply analysis is actually employed in deriving such theory, as developed in Chapter 4 of The Theory of Political Economy (TPE). This is all the more puzzling in the light of the following two facts: 1) in his 1868 correspondence with Jevons, Fleeming Jenkin provides a complete geometrical solution of the exchange equilibrium problem based on the use of demand and supply curves, but his suggestion is wholly neglected by Jevons in the first edition of TPE (1871); 2) in his 1874 open letter to Jevons, Walras explicitly criticizes his correspondent for his defective treatment of the "laws of supply and demand", suggesting an alternative analytical solution of the exchange problem based on the use of demand and supply functions; yet Jevons entirely disregards Walras's remarks in preparing the second edition of TPE (1879). This paper compares Jevons's, Jenkin's and Walras's approaches to the exchange equilibrium problem, explaining the analytical and epistemological reasons that underlie Jevons's neglect of his correspondents' criticism and advice.