Denis Papin was a French physician, born at Blois in 1647. He studied medicine in Paris, and visited England to associate himself with Robert Boyle in his experiments, and was admitted a member of the Royal Society in 1681. After the Revocation of the Edict of Nantes, being a Huguenot, he could not return to France, so took refuge in Germany, where he was well received by the Landgrave of Hesse, who gave him the professorship of mathematics in the University of Marburg. He was the first to apply the safety-valve and the piston to the steam engine. He showed that the upward and downward alternate movement of the piston might be employed with effect for the transmission of force. If after the rise of the piston a vacuum could be created below, the piston would fall with the pressure of the atmosphere above. In order to create this vacuum he proposed to explode gunpowder under the piston; but he saw himself that this method of creating a void was clumsy and impracticable. He then sought to exhaust the air by means of an hydraulic engine moved by a water-wheel, and he proposed a machine of this sort to the Royal Society in 1687; but he also suggested a means of producing the required vacuum by condensation of steam. Much about the same time the same idea occurred to Thomas Savery, a native of Modbury, a member of an ancient Devonshire family, coming originally from Halberton, whence John Savery moved to Totnes. Probably through the wool and clothing trade, he amassed a considerable estate in the reign of Henry VIII. In the sixteenth century the heiress of Servington of Tavistock married into the family. In 1588, Christopher Savery, the head of the family, resided in Totnes Castle, not then dismantled; and for a period of nearly forty years the town was represented in Parliament by members of the Savery family. One Christopher served as Sheriff of Devon in 1620. His son was a colonel under Oliver Cromwell.