142 AN EMPIRICAL STUDY OF GYRATING BODIES. 



the standard and rise. I have not been able to make 

 mine do so. 



THE GYROSCOPE NOT A MODIFIED PENDULUM. 



General Barnard says that the gyroscope belongs to 

 the class of instruments of which it stands at one end 

 and the pendulum at the other. 



It seems to me that they are radically different. In 

 the pendulum everything depends upon the length of the 

 rod (distance from centre of oscillation to point of sup- 

 port), and nothing upon the weight of the bob. In the 

 gyroscope, the rate of the gyratory motion, and also 

 that of the descending motion, changes as the weight 

 changes, other things being constant, while the distance 

 from the point of support to the load may be made longer 

 or shorter without effect, provided the angle a (fig. 8) is 

 unchanged. 



In Thomson and TaiV s Natural PJdlosophy we are 

 told that the motion of the gyroscope, top, etc., may be 

 represented by the rolling of a cone fixed in the body, 

 on another cone fixed in space. 



This statement to represent actual conditions must be 

 supplemented by the words " whose vertical angle is not 

 fixed, but which, in the most general exemplification of 

 such bodies, passes from infinitely near 0° to 180°, and 

 from that to 0°." 



This is a corollory of the principle that a gyrating 

 body, in general, yields to the force which tends to make 

 it revolve around an axis perpendicular to its first axis. 



THE TOP. 



The theory of the top is regarded as very difficult. J. 

 C. Maxwell says the problem of the top surpasses that 

 of the precession of the equinoxes. 1 



In my study of this instrument I have used the disk 



1 Transactions of Roy. Soc. Ed. Vol. — , page — . 



126 



