GAS ENGINES 363 



continued to the gear-box which contains the gears for alter- 

 ing the speed of the driving wheels to that of the engine. In 

 the rear of the gear-box 

 is the propelling shaft, 

 which connects by 

 means of bevel gears, a 

 special device of gears 

 called a differential, to 

 the axle of the driving 

 wheel to which the power 

 of the engine is trans- 

 mitted. The engines, 

 gear-box, etc., are all 

 mounted on the frame of 

 the car. Between the FIG. 179. Valves and Valve Cages. 

 frame and axle are the 



springs which absorb the shocks caused by bumping over 

 rough roads. 



Sometimes the power is transmitted from gear-box to axle 

 by means of chains. In this case there is a sprocket wheel on 

 a shaft behind the gear-box, and a larger sprocket wheel 

 attached to the hubs of the driving wheels. The axles of the 

 driving wheels are fixed to the springs and wheels revolve 

 around them. 



409. Other Parts of Motor Car. The other parts of an 

 automobile which need a brief description are the starting 

 handle, the carbureter, silencer, governor, magneto, and 

 gears. 



Starting Handle. In front of the car there is a handle 

 attached to a tube which terminates in a clutch. A powerful 

 spring keeps this clutch from a second one that is keyed to the 



