Question for March 4, 2010

X was one of several famous French mathematicians during the time of Napoleon. His most famous contribution, which was actually developed to solve heat equation but is now used in the original form or some derived form in almost every applied mathematics field. The original article was submitted to the Academy of Sciences in Paris, but was heavily criticized by the reviewers (most strongly by Lagrange among others including Laplace, Legendre and Malus). In their report, the committee concluded: "the manner in which the author arrives at these equations is not exempt of difficulties and [...] his analysis to integrate them still leaves something to be desired on the score of generality and even rigour." He later succeeded Laplace as the president of Academy of Science and his work including the previously rejected work was then published in what is now considered a classic.

Identify X and the contribution.