Francis Ysidro Edgeworth
1845 - 1926
Edgeworth, a professor at King's College London, was a friend of Jevons'. His own contributions included the idea of the indifference curve and important insights into economic equilibrium, whilst he also made contributions to the earliest developments in mathematical statistics.
Edgeworth and Jevons were known to take walks together on Hampstead Heath. Edgeworth lived around that time at 5 Mount Vernon in Hampstead.