CAPTIVE MOLECULES 



of Savery; to the Frenchman, therefore, must be given 

 the credit of hitting upon two important principles 

 which made feasible the modern steam engine. Papin 

 constructed a model consisting of a small cylinder in 

 which a solid piston worked. In the cylinder beneath 

 the piston was placed a small quantity of water, which, 

 when the cylinder was heated, was turned into steam, 

 the elastic force of which raised the piston. The cylinder 

 was then cooled by removing the fire, when the steam 

 condensed, thus creating a vacuum in the cylinder, into 

 which the piston was forced by the pressure of the 

 atmosphere. 



Such an apparatus seems crude enough, yet it in- 

 corporates the essential principles, and required but the 

 use of ingenuity in elaborating details of the mechanism, 

 to make a really efficient steam engine. It would appear, 

 however, that Papin was chiefly interested in the theo- 

 retical, rather than in the really practical side of the 

 question, and there is no evidence of his having pro- 

 duced a working machine of practical power, until 

 after such machines worked by steam had been con- 

 structed elsewhere. 



THOMAS NEWCOMEN S IMPROVED ENGINE 



As has happened so often in other fields, Englishmen 

 were the first to make practical use of the new ideas. 

 In 1705 Thomas Newcomen, a blacksmith or ironmon- 

 ger, and John Cawley, a plumber and glazier, patented 

 their atmospheric engine, and five years later, in the 

 year 1710, namely, Newcomen had on the market an 



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