THE CONQUEST OF NATURE 



the cylinder, the pressure of the air from above thrust 

 the cylinder down, this being the actual working agent. 

 It was for this reason that the Newcomen engine was 

 called, with much propriety, a pneumatic engine. The 

 action of the engine was very slow, and it was necessary 

 to employ a very large piston in order to gain a consider- 

 able power. 



The first idea that occurred to Watt in connection 

 with the probable improvement of this mechanism did 

 not look to the alteration of any of the general features 

 of the structure, as regards size or arrangement of cylin- 

 der, piston, or beam, or the essential principle upon 

 which the engine worked. His entire attention was fixed 

 on the discovery of a method by which the loss of heat 

 through periodical cooling of the cylinder could be 

 avoided. We are told that he contemplated the subject 

 long, and experimented much, before he reached a satis- 

 factory solution. Naturally enough his attention was 

 first directed toward the cylinder itself. He queried 

 whether the cylinder might not be made of wood, 

 which, through its poor conduction of heat, might better 

 equalize the temperature. Experiments in this direc- 

 tion, however, produced no satisfactory result. 



Then at last an inspiration came to him. Why not 

 connect the cylinder with another receptacle, in which 

 the condensation of the steam could be effected ? The 

 idea was a brilliant one, but neither its originator nor 

 any other man of the period could possibly have realized 

 its vast and all-comprehending importance. For in 

 that idea was contained the germ of all the future of 

 steam as a motive power. Indeed, it scarcely suffices 



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