Puy-du-Dôme (564), a department in Central France, in the upper valley of the Allier, on the slopes of the Auvergne Mountains. The soil is poor, but agriculture and cattle-breeding are the chief industries; in the mountains coal and lead are found, and there are many mineral springs; there are paper and oil manufactures. The principal town is Clermont-Ferrand (45), where Peter the Hermit preached the first crusade.