GASOLENE 25 



cool off as completely by exhaustion. Or in other words, 

 the efficiency of an engine depends upon getting the 

 longest possible range of pressure and temperature be- 

 tween the beginning and the end. The automobile is 

 run by two horses, heat and cold. The higher the 

 heat and the lower the cold, the greater the power. 



We can use any gas we like for our engine, for all 

 gases behave about the same. Naturally steam was the 

 first gas used in the cylinder. But steam has to be 

 made separately in a boiler and then conducted into 

 the cylinder. And a boiler is a bulky thing and oc- 

 casionally blows up. To heat the boiler there must 

 be a furnace and to the furnace there must be attached 

 a tall chimney to create a draft. A pile of coal must 

 be at hand and a stoker to shovel it in. If the engine 

 is large and complicated there must be an engineer, duly 

 licensed and a member of the union. There is inevit- 

 ably tremendous waste of potential energy, for the steam 

 has at best a small fall of temperature while it is doing 

 its work in the cylinder. It is not nearly so hot as the 

 furnace gases which are lost up the chimney. 



If in some way we could combine the furnace and 

 the boiler and burn the fuel in the cylinder itself, right 

 where we want to do the work, we could take ad- 

 vantage of the high temperature to get high pressure 

 and simplify the apparatus. This is just what is done 

 in the gasolene engine. The cylinder is made the fur- 

 nace. Fill it up, by a jerk of the piston rod, with air 

 mingled with a little vaporized gasolene, set it afire with 

 an electric spark. The carbon and the hydrogen of the 

 gasolene unite with the oxygen of the air, forming car- 



