42 MOTIVE POWER OF HEAT. 



to England. Savery, Newcomen, Smeaton, the 

 famous Watt, Woolf, Trevithick, and some other 

 English engineers, are the veritable creators of the 

 steam-engine. It has acquired at their hands all 

 its successive degrees of improvement. Finally, it 

 is natural that an invention should have its birth 

 and especially be developed, be perfected, in that 

 place where its want is most strongly felt. 



Notwithstanding the work of all kinds done by 

 steam-engines, notwithstanding the satisfactory 

 condition to which they have been brought to-day, 

 their theory is very little understood, and the at- 

 tempts to improve them are still directed almost 

 by chance. 



The question has often been raised whether the 

 motive power of heat* is unbounded, whether the 

 possible improvements in steam-engines have an 

 assignable limit, a limit which the nature of 

 things will not allow to be passed by any means 

 whatever ; or whether, on the contrary, these im- 

 provements may be carried on indefinitely. We 



* We use here the expression motive power to express 

 the useful effect that a motor is capable of producing. 

 This effect can always be likened to the elevation of a 

 weight to a certain height. It has, as we know, as a 

 measure, the product of the weight multiplied by the 

 height to which it is raised. 



