see:  Economic Theory in Retrospect
5th Edition
Mark Blaug
1997  p.309
"18 Gossen's second law

Our fourth and last pioneer is Hermann Heinrich Gossen, whose _Laws of Human
Relations_, published in Germany in 1854, went completely unnoticed at the
time-Bitterly disappointed with the poor reception of his work - which, he
had claimed, would do for economics what Copernicus had done for astronomy -
Gossen recalled all the unsold copies of the book and destroyed them.
Inconsequence, when Jevons rediscovered the book in 1878, he and Walras only
managed to find a few copies still remaining. Walras was amazed to see that
Gossen had not only formulated the principle of diminishing marginal utility
and graphed it but had also grasped the distinction, which Dupuit never did.
between a negatively inclined marginal utility curve and a negatively
inclined demand curve. Similarly, Jevons was astonished to find that Gossen
had formulated a theory of the marginal disutility of labour strikingly
similar to his own, including a virtual replica of his own diagram of the
equalisation of the marginal utility of the product and the marginal
disutility of work .... Both of them were particularly struck by what soon
came to be called Gossen's 'second law': 'A person maximises his utility
when he distributes his available money among the various goods so that he
obtains the same amount or satisfaction from the last unit of money spent
upon each commodity.' "

Michael Ambrosi