

4i8 



FARM MOTORS 



the hot tube and the electric spark. The latter type, which 

 is most popular in America at present, may be divided 

 into two classes, the contact spark and the jump spark. 

 Contact spark (Fig. 306). It has been noticed that 

 when a break is made in an electric circuit a spark takes 

 place, and it is upon this principle that the contact gaso- 

 line ignitor depends. The charges of the fuel mixture 



FIG. 306 CONTACT-SPARK IGNITOR FIG. 307 JUMP-SPARK IGNITOR 



are ignited by causing 

 this break to be made 

 inside of the cylinder. 

 The quicker this break 

 is made, the more pro- 

 nounced the spark. The 

 spark is always made 

 larger and more pro- 

 nounced by including in 

 the circuit a spark coil. 

 Jump spark. The 

 jump-spark i-gnitor 

 (Fig. 307) has within 

 the cylinder two points 

 insulated from each 

 other and separated by 



SWITCH 



FIG. 308 WIRING SYSTEM FOR JUMP- 

 SPARK IGNITION 



