Lemercier, Jacques (zhäk ləmĕrsyāˈ) [key], c.1585–1654, French architect, one of the group that evolved a classical mode of expression for French architecture. In Italy (c.1607–1614) he was strongly influenced by the architecture of Rome. With Cardinal Richelieu as his patron, Lemercier received his greatest opportunities as a designer of churches for the Jesuits. His chief remaining work is the church of the Sorbonne, Paris (1635), inspired by Giacomo della Porta's designs and containing a dome which furnished a model for that of the Church of the Invalides. It was built at Richelieu's order, as were Richelieu's Paris residence, later transformed into the Palais-Royal, and the entire town of Richelieu, an ambitious piece of 17th-century town planning. In Paris at the palace of the Louvre, Lemercier built the Pavillon de l'Horloge, and he superseded (c.1646) François Mansart in supervising the construction of the Church of Val-de-Grâce.