In 1798 de Prony refused Napoleon's request that he join his army of invasion to Egypt. Fourier, Monge and Malus had agreed to be part of the expeditionary force and Napoleon was angry that de Prony would not come.
In 1798 de Prony tumanggi Napoleon ang kahilingan na siya sumali sa kanyang hukbo ng mga pagsalakay sa Ehipto. Fourier, Monge at Malus had sumang-ayon na maging bahagi ng pinadala ng lakas at Napoleon ay nagagalit na de Prony ay hindi dumating.