GAS ENGINES 



I8 5 



The steam engine as seen on our railroad trains is 

 very complex, and cannot be discussed here ; in principle, 

 however, it is identical with that just described. Fig- 

 ure 129 shows a steam harvester at work on a modern 

 farm. 



In both engine and turbine the real source of power is 

 not the steam but the fuel, such as coal or oil, which converts 

 the water into steam. 



1 80. Gas Engines. Automobiles have been largely re- 

 sponsible for the gas engine. To carry coal for fuel and water 

 for steam would be impracticable for most motor cars. 

 Electricity is used in some cars, but the batteries are heavy, 

 expensive, and short-lived, and are not always easily replace- 



FlG. 129. Steam harvester at work. 



able. For this reason gasoline is extensively used, and in the 

 average automobile the source of power is the force generated 

 by exploding gases. 



It was discovered some years ago that if the vapor of 

 gasoline or naphtha was mixed with a definite quantity of air, 

 and a light was applied to the mixture, an explosion would 

 result. Modern science uses the force of such exploding gases 

 for the accomplishment of work, such as running of automo- 

 biles and launches. 



