670 ME. C. W. SIEMENS ON UNIFORM ROTATION. 



which is equivalent to forcing a valve rod or lever through one decimetre space in ten 

 seconds against a resistance of 120 kilograms. 



This force exceeds by far what is usually required of a governor, and fits the new 

 instrument for the accomplishment of objects which hitherto could not be attempted, 

 such for instance as regulating the power of engines by the link motion or other variable 

 expansion gear (whereby a considerable saving of fuel may be effected), or moving the 

 gate of a water-wheel. 



The most striking feature of this governor is, however, the rapidity with which a 

 readjustment between power and load of an engine is effected ; experiment has proved 

 that two-thirds of the total load upon an engine may he suddenly throvm off without pro- 

 ducing any visible change in its rotation. It must be borne in mind that the variation of 

 1 per cent., which was assumed in calculating the power of the instrument, applies only 

 to the short period often seconds, during which the readjustment of the valve is effected, 

 after which the cup and, with it, the engine returns to its normal rate of rotation ; but an 

 increase or decrease of speed of 1 per cent, during ten seconds is so small a total amount 

 that it is not perceptible to the eye, and may be regarded as non-existing for practical 

 purposes. 



A uniform velocity of engines, such as is secured by this instrument, is of consider- 

 able practical importance in spinning, grinding com, and other manufacturing operations, 

 because it not only prevents breakages and irregularities in the quality of the work pro- 

 duced, but it enables manufacturers to attain to the maximum speed at which their 

 work can be produced. 



It has been shown that the rotating cup is not sensitive to tipping, a circumstance 

 rendering the gyrometric governor also applicable to marine engines, which are much in 

 need of a means for maintaining a uniform speed, particularly where the screw propeller 

 is used, which, in being raised by waves above the water, allows the engine to fly off at 

 a dangerous speed. 



The gyrometric cup appears therefore to be equally applicable for maintaining powerful 

 machinery at a nearly uniform velocity, and for obtaining the higher uniformity of rota- 

 tion requisite for philosophical and telegraphic instruments. 



