MR. C. W. SIEMENS ON tTNIFORM EOTATION. 



667 



This result shows that the spring employed was decidedly too weak, producing a 

 decrease of s])eed with increase of power. 



A more careful adjustment of the spring would improve these results, which suffice, 

 however, to prove the capabilities of the instrument. 



It appears at first sight as though the friction of the cup upon the threads of the 

 screw must interfere with its automatic adjustment; but this is practically not the case, 

 owing to the circumstance that small fluctuations in the resistance continually occur, 

 causing torsional oscillations of the cup, the mean of which must be its true position 

 notwithstanding friction, which friction moreover is reduced to a minimum, owing to the 

 suspension of the weight by the spring. 



Another interesting quality of the gyrometric cup is its comparative indifference to a 

 vertical position ; it may, indeed, be tipped very considerably without interfering Avith 

 the uniform overflow all round, and the time of its rotations is diminished only in the 

 ratio of the square roots of the vei'tical mean heights, or it is 



n' : n-=\/h : y/h cos /3, 

 or for a tipping angle /3= 3°, 



n':n=l : 1-0007, 



showing that no particular care is requisite to place the instrument upon a horizontal 

 foundation. 



Gyrometric Governor. — ^The most useful practical application of this instrument is 

 that of regulating the power and velocity of steam-engines. A cup of very large dimen- 

 sions, provided with several belts of check-vanes and with the automatic dip arrangement, 

 might be conceived which, being connected by gearing with the main shaft of an 

 engine, would limit its velocity by absorbing directly all its surplus power. This sur- 

 plus power would appear in the cup-chamber in the form of molecular motion or heat. 



