if the velocity of the liquid is a quarter period ahead of that of
the pendulous system, then the following effects will occur.
Consider the action at an instant when the pendulous system has
a large deflection, and there are equal amounts of liquid in the two
tanks, Fig. 28. While the pendulous system is moving from this
position to the equilibrium position, an excess of liquid rises in the
tank that was the lower, the excess being maximum when the
pendulous system is in the equilibrium position, Fig. 29. During
this quarter period, the distance between the center of mass of the
pendulous system and the vertical line through the axis of vibra
tion is being diminished. Hence, the torque urging the pendulous
system toward the equilibrium position is being diminished faster
than it would be if the liquid were not flowing.
While the pendulous system is moving from the equilibrium
position, Fig. 29, to the end of the swing, Fig. 30, the excess of