In one aspect, an apparatus for damping the torsional excitation of a drive shaft is provided. The apparatus includes: a member secured to one end of the drive shaft and extending along the drive shaft; and damping means secured to the other end of the drive shaft for damping vibration of the end of the member remote from the securing of the member to the one end of the drive shaft. A hydraulic circuit for damping the vibration of a component in a first dimension, the circuit including: a pair of hydraulic cylinders disposed so that the actions of the pistons of the cylinders oppose one another in the first dimension, the pistons communicating with the component; and a fluid flow path between the cylinders, vibration of the component in the first dimension causing fluid flow between the cylinders to damp the vibration.