464 



THE STEAM-ENGINE. 



Fig. 22. 



revolving upon it. If the balls I are drawn outward from the vertical axis, it 

 is evident that the ends F of the levers will be drawn down, and therefore the 

 pivots E likewise drawn down. In fact, the angles E F H will become more 

 acute, and the angle F E F more obtuse. By these means the sliding ring E 

 will be drawn down. To this sliding ring E, and immediately above it, is at- 

 tached a grooved collar, which slides on the vertical spindle upward and down- 

 ward with the ring E. In the grooved collar are inserted the prongs of a fork 

 K, formed at the end of the lever K L, the fulcrum or pivot of the lever being 

 at L. By this arrangement, when the divergence of the balls I causes the 

 collar E to be drawn down, the fork K, whose prongs are inserted in the groove 

 of that collar, is likewise drawn down ; and, on the other hand, when, by 

 reason of the balls I falling toward the vertical spindle, the collar E is raised, 

 the fork K is likewise raised. 



The ascent and descent of the fork K necessarily produce a contrary motion 

 in the other end N of the lever. This end is connected by a rod, or system 

 of rods, with the end M of the short lever which works the throttle-valve T. 

 By such means the motion of the balls I, toward or from the vertical spindle, 

 produces in the throttle-valve a corresponding motion ; and they are so con- 

 nected that the divergence of the balls I will cause the throttle-valve to close, 

 while their descent toward the vertical spindle will cause it to open. 



These arrangements being comprehended, let us suppose that, either by 

 reason of a diminished load upon the engine or an increased activity of the 

 boiler, the speed has a tendency to increase. This would impart increased 

 velocity to the grooved wheel A B, which would cause the balls I to revolve 

 with an accelerated speed. The centrifugal force which attends their motion 

 would therefore give them a tendency to move from the axle, or to diverge. 

 This would cause, by the means already explained, the throttle-valve T to be 

 partially closed, by which the supply of steam from the boiler to the cylinder 

 would be diminished, and the energy of the moving power, therefore, mitigated. 

 The undue increase of speed would thereby be prevented. 



If, on the other hand, either by an increase of the load, or a diminished 

 activity in the boiler, the speed of the machine was lessened, a corresponding 

 diminution of velocity would take place in the grooved wheel A B. This 



