Puy de Dôme
Puy de Dôme, extinct volcano of the Massif Central and the second highest peak (4,806 ft/1,465 m) of the Auvergne Mts., central France, W of Clermont-Ferrand. Crops are raised on the lower slopes; the highlands are used as pasturage. On its level summit (it has no crater) are a meteorological observatory and the ruins of a temple of Mercury. There Florence Périer conducted (1648), upon instructions of his brother-in-law, Blaise Pascal, the famous experiment that confirmed Torricelli's theory on air pressure (see Pascal's law).