In 1680 Papin, who like Solomon de Caus had brought his scientific conceptions to England in the hope of their furtherance, was admitted on the recommendation of Boyle to a fellowship of the Royal Society. After a short absence he returned to London in ’84 and filled for a time the post of curator to the society, meeting, doubtless, in that capacity the leading scientists of the day and coming in touch with all the practical efforts of English inventors. During his stay here he worked with enthusiasm at the production of a prime mover, and when he left in ’87 for a mathematical professorship in Germany he continued there his researches and experienced repeated failures. In a paper published in ’88 he showed a clear conception of a reciprocating engine actuated by atmospheric pressure, and in ’90 he suggested for the first time the use of steam for forming the vacuum required. As water, he wrote, has elasticity when fire has changed it into vapour, and as cold will condense it again, it should be possible to make engines in which, by the use of heat, water would provide the vacuum which gunpowder had failed to give. This memorable announcement gave a clear direction to the future development of the heat engine. Steam was the medium best suited for utilizing the expansive power of heat generated by the combustion of fuel; steam was the medium which, by its expansive and contractile properties, could be made to impart a movement _de va et vient_ to a piston. Though Papin did not succeed in putting his idea into practical form his conception was of great value, and he must be counted as one of the principal contributors to the early development of the steam engine. His life was an accumulation of apparent failures ending in abject poverty. To-day he is honoured by France as the inventor of the steam engine, and at Blois a statue has been erected and a street named to his memory. Before the end of the century an effective engine had been produced, in England. In 1698 Thomas Savery, a Devonshire man, obtained a patent for “a new invention for raising of water and occasioning motion to all sorts of millwork by the impellent force of fire.” Before the king at Hampton Court a model of this invention was displayed, and the importance of the new discovery was soon realized by the landed classes; for in the following year an act of parliament was passed for the encouragement of the inventor and for his protection in the development of what, it was recognized, was likely to prove of great use to the public. In the same year Savery published a pamphlet called _The Miner’s Friend_, and republished it, with additions, in 1702. This pamphlet contained a full and clear description of his engine; but significance has been attached to the omission from it of any claim that it embodied a new idea. The omission may be accidental.