WATT. 37 1 



consequently the velocity of the engine increases; 

 their divergence pushes the collar up the spindle, its 

 axis, and as it rises, it closes, by means of cranks, a 

 valve called the " throttle-valve," in the pipe which 

 conveys the steam from the boiler to the cylinder, and 

 this lessens the supply of steam : the motion of the 

 engine is thus reduced, the centrifugal force is abated, 

 the balls approach the spindle again, the collar de- 

 scends, the throttle- valve is gradually opened, and the 

 supply of steam again slowly increased, but never be- 

 yond the quantity required, because as soon as that is 

 exceeded, the increase of centrifugal force causes 

 the balls to diverge, the collars to rise, and the valve 

 to close. Thus the engine itself provides for its con- 

 tinuing in the state of perfect adjustment required. As 

 long as its motion continues uniform, the balls revolve 

 at the mean distance from their axis without either 

 receding or approaching, and the supply of steam con- 

 tinues the same. As soon as the motion becomes ex- 

 cessive, they diverge, and the supply of steam is dimi- 

 nished ; as soon as the motion becomes defective, they 

 converge, and the supply of steam is increased. But 

 further, the baHs themselves, by their increased motion, 

 absorb part of the force, independent of their action on 

 the throttle^valve, and so contribute to the adjustment* 

 The sagacious inventor soon satisfied himself that 

 he had almost created a new engine of incalculable 

 power, universal application, and inestimable value. 

 But he had not the funds either to try his invention 

 upon an adequate scale so as to bring it into use, or to 

 secure his property in it by obtaining a patent. After 

 some repulses, he happily met with Dr. Roebuck, a 



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