GOVERNOR. 



every undue increase of speed diminishes the supply of steam, and 

 moderates the velocity; and every undue decrease of speed 

 increases the supply of steam, and augments the velocity. In 

 this manner the action of the governor keeps the engine constantly 

 moving at a regulated rate. 



44. The manner in which the governor opens the throttle valve 

 will be still more easily understood by the aid of fig. 27. 



A small grooved wheel A B is attached to a vertical spindle 

 supported in pivots or sockets c and D, in which it is capable of 

 revolving. An endless cord works in the groove A B, and is 

 carried over proper pulleys to the axle of the fly-wheel, where it 

 likewise works in a groove. When this cord is properly tightened, 



Fig. 27. 



the motion of the fly-wheel will give motion to the wheel A B, so 

 that the velocity of the one will be subject to all the changes inci- 

 dental to the velocity of the other. By this means the speed of 

 the grooved wheel A B may be considered as representing the 

 speed of the fly-wheel, and of the machinery which the axle of 

 the fly-wheel drives. 



It is evident that the same end might be obtained by substi- 

 tuting for the grooved wheel A B a toothed wheel, which might be 

 connected by other toothed wheels, and proper shafts and axles 

 with the axle of the fly-wheel. 



37 



