WILLIAM B. D WIGHT. 07 



The latter theory is simple and seems to me the more 

 acceptable, though the perfect vertically and smooth- 

 ness of the face of the sand, and the entire absence of 

 any disturbance of its stratification, seem difficult to rec- 

 oncile with the violent grinding motion of a fault. 



FEBRUARY 25, 1885— THIRTY-FOURTH STATED MEETING. 



Prof. W. B. Dwight, chairman, presiding; thirteen 

 members and guests present. 



Prof. Dwight presented to the Museum five specimens 

 of materials from Clark's clay-beds. 



C. B. Warring, Ph.D., read a paper on precession and 

 nutation, completing his discussion of the motions of the 

 Gyroscope and other rotating bodies. The several parts 

 of this discussion are brought together in the following 

 paper : 



AN EMPIRICAL STUDY OF GYRATING BODIES. 



BY C. B. WAKKING, Ph.D. 



The Gyroscope, the Top, the Gyrostat, the Gyrocycle, Bohnenbergher 

 Machine, our Earth, Precession and Nutation, Gyrostatic Balance, 

 Gyrostatic Compass and Gyroscopic Pendulum. Illustrated by more 

 than fifty figures " from life." 



GYRATING BODIES. 



A gyrating body is a body revolving on an axis x»ass- 

 ing through its centre of gravity, and acted upon by a 

 continuous force 1 tending to make it revolve on another 

 axis at right angles to the first. This second axis may, 

 or may not, pass through the centre of gravity. 



Of such bodies the top is the best known example. 

 The gyroscope, the gyrostat, the gyrocycle, and the 

 Bohnenbergher machine, complete the list. The earth 



1 " Continuous force," because as soon as the force ceases to act, gyrative peculiarities 

 cease, as will be shown hereafter. And, furthermore, in all the gyrating bodies in actual 

 operation, the force tending to make them revolve around a second axis is continuous. 



sx 



