120 THE SCIENTIFIC PAPERS OF 



This result shows that the spring employed was decidedly too 

 weak, producing a decrease, of speed 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 adjust- 

 ment ; 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 com- 

 parative indifference to a vertical position ; it may, indeed, be 

 tipped very considerably without interfering with the uniform 

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

 in the ratio of the square roots of the vertical mean heights, or 

 it is ri : n = JOT: >Jh cos /3, or for a tipping angle /3 = 3, 

 ri : n = 1 : 1*0007, showing that no particular care is requisite 

 to place the instrument upon a horizontal foundation. 



G-YHOMETRIC GOVERNOR. The most useful practical applica- 

 tion of this instrument is that of regulating the power and velocity 

 of steam-engines. A cup of very large dimensions, provided with 

 several belts of check-vanes and with the automatic dip arrange- 

 ment, might be conceived which, in being connected by gearing 

 with the main shaft of an engine, would limit its velocity by 

 absorbing directly all its surplus power. This surplus power 

 would appear in the cup-chamber in the form of molecular motion 

 or heat, and would have to be got rid of by the application 

 of cooling agents, if the natural dispersion of heat by radiation 

 would no longer suffice to keep down the temperature. This 

 would, however, be a wasteful proceeding, and it becomes necessary 

 to operate, not upon the power produced, but rather upon the 

 source of power, by rendering it always equal to the accidental 

 resistance or load in order to maintain uniform velocity. The 

 arrangement adapted for this purpose is represented by Plate 20, 

 Fig. 2, and Plate 21, Figs. 3, 4, 5 and 6. 



S is the main shaft of the engine, which imparts motion to the 



