1887.] NEW YORK ACADEMY OF SCIENCES. 133 



chromate battery, which is said to be constant for only fifteen 

 or twenty minutes, will answer our purpose. 



If, while V is uniform, we attach larger or smaller weights, it 

 will be found that here, also, A oo - ; or, as v is constant, h 



Hence, I conclude that a frictiouless gyrating body does yield 

 to the "second force." 



IV. — If the "second force " be gradually lessened while the 

 instrument is moving horizontally and falling, the latter (the 

 falling) will cease, and the instrument gradually rise to a hori- 

 zontal position. The horizontal movement will not change its 

 sign, but will gradually grow less, and become zero when the 

 " second force " becomes zero. 



Proof. — Let the weight (or "second force") be a cup of shot. 

 When in motion, open (by burning off a thread) a valve in the 

 bottom of the cup; as the shot runs out, the instrument begins 

 to rise. It will go considerably above its starting position. 



V. — When in operation, the gyroscope is apparently destitute 

 of momentum. 



Proof. — Attach by a thread a weight sufficient to cause rapid 

 horizontal movement, then when in rapid motion burn off the 

 thread: the instrument stops suddenly. 



From these we deduce the following laws: 



1st. A gyrating body tilts in the direction of the " second 

 force,'' whether this is uniform or accelerated. 



2d. It tilts in the opposite direction if the force is a diminish- 

 ing one. 



3d. When the "second force" ceases, the precessional move- 

 ment ceases, not gradually, but at the same time. 



4th. No tilting, no gyration ; or, in other words, no nutation, 

 no precession. 



Nidation. 



The earth is a gyrating body, and consequently subject to the 

 laws of such bodies. 



Tiie "second force" in its case, is the result of the moon's and 

 fiun's attraction on the equatorial protuberance, and its effect 



