C. B. WARRING. 197 



in the plane of the wheel. It will show no tendency to 

 stop, and will offer no resistance, although the plane of 

 original rotation is rapidly changing its direction. Stop 

 the wheel ; you will find no change, the instrument re- 

 volves around the cross axis equally well whether the 

 wheel is rotating on its own axis or not. 



It was to this experiment that I referred in the first of 

 my papers when refuting the belief that there is a pecu- 

 liar and inherent power of resistance in rotating bodies. 



By way of contrast, loosen the turn-table and again at- 

 tempt to go through the above experiments. 



THE GYROSCOPIC PENDULUM. 



The gyroscopic pendulum (fig. 48), consists of a rigid 

 rod supporting, in place of the usual bob, a rigidly con- 

 nected gyroscope. 



If the wheel is set to revolving, and then the pendu- 

 lum set to beating, it will not move back and forth in 

 one plane, but will describe a curious series of curves. 

 What is their rationale ? 



Our tee-square will prove helpful here. Suppose fig. 

 49 to represent one of these squares supported at A, and 

 in different positions. The arms are placed in the plane 

 of the vibrations. Imagine a horizontal line, shown by 

 the dots, to pass through the point p, and to remain 

 horizontal in all positions of the tee. If the instrument 

 is placed at some distance from the centre of the arc, as 

 represented on the right hand side of the diagram, a 

 will be some distance above the horizontal line. As the 

 tee goes towards the middle of the arc, a falls towards 

 that line, and, as it passes on to the left, a falls farther 

 and farther below it, till the instrument ceases to rise. 

 What is true of a is true of b, only in the opposite sense. 

 When a goes down b goes up, and vice versa. The 

 result is that a and b make a partial revolution about 



181 



