88 



THE ANIMAL AS A MACHINE. 



engines, respectively.* The engine fully utilizing, 

 ideally, but two and one half pounds of steam and 

 one fourth of a pound of coal per horse-power per 

 hour practically demands six to eight times this 

 amount, even when of the best construction ; while 

 the average engine probably utilizes but one pound in 

 ten, and often but one in twenty, wasting from ninety 

 to ninety-five per cent of all the heat from its furnaces. 

 The gas-engine gives higher thermodynamic perform- 

 ance than the steam-engine ; but it compensates this 

 advantage by loss, through a " water-jacket," of one- 

 half of all the heat that it should completely transform 

 into useful work.f No method is yet discovered 

 of imitating nature in direct conversion of heat 

 into other forms of energy without waste ; and our 

 production of light, in our most recent and most 

 wonderful inventions, involves the same waste by the 

 intermediate use of the heat-engine for primary trans- 

 formation of heat into mechanical energy, in turn to 

 be converted, with great efficiency, into electricity, 

 thence to be once more transformed, with great waste 

 again, into light. The direct evolution of light, 

 purely, or of electricity alone and without loss, from 

 fuel oxidation, though it is constantly performed by 

 nature, is as yet beyond the power of man. Could 

 these problems of life be solved, power and light 

 would cost us but a small fraction of their cost to-day ; 

 and the exhaustion of our coal-beds would be deferred 



*" Steam and its Rivals," R. H. Thurston: Forum, May 1888, 

 p. 341. Also "Manual of the Steam-engine," vol. i. (New York, 

 J. Wiley & Sons, 1890). 



f " Last Days of the Steam-engine," R. H. Thurston: North 

 American Review^ July 1889. 



