SCIENCE OF THRESHING. 



I2 3 



A represents the cylinder provided with a piston, 

 B, while C is the piston rod. A link or connecting 

 rod, D, is jointed or pivoted to the end of another 

 link or crank arm, E, the other end of the latter 

 being rigidly secured to a shaft, F, which revolves 

 in fixed bearings. When the piston, B, is at the end 

 of the cylinder farthest from the crank or con- 

 necting rod, which is commonly called the head end 

 of the cylinder, the piston rod, C } connecting rod D 

 and crank E are all in the same straight line. As the 

 piston returns to the other end of the cylinder, the 

 crank arm is caused to revolve about the end fixed 

 to the shaft and so imparts a continuous motion to 

 the latter. The parts which move back and forth are 

 called the reciprocating parts. The outer end of the 

 cylinder or head is called the outboard or cylinder 

 end; the other end is called the inboard or crank end. 

 If the crank moves in the direction indicated by the 

 arrow it is said to run over. If it moves in the other 

 way it is said to run under. H is the head end and G 

 the crank end of the cylinder; N andNi are the cyl- 



