My confidence in Cournot as aneconomistwas shaken when I found that his mathematicsreI[ncreasing] R[eturns]led inevitably to things which do not exist and have no near relation to reality. One of the chief purposes of my Wander‐jahre among factories, etc., was to discover how Cournot's premises were wrong. The chief outcome of my work in this direction, which occupied me a good deal between 1870 and 1890, is in the ‘Representative firm’ theory,.the supplementary cost analysis,.as well as the parts [of thePrinciples] that directly relate to supply price for I. R. Marshall to A. W. Flux, 7 March, 1898, inMemorials, (1872–1923), p