It has long been realised that there is a precise analogy between the properties of vibrating mechanical systems and those of alternating current electric circuits. It was from this analogy that the concept of “ mechanical impedance ” (more appropriately termed “ dynamic stiffness ”) was derived, thus enabling the theory of certain types of mechanical vibration, notably torsional motion, to be put on a more rational basis.

By means of analogous elements it is possible to represent a mechanical vibrating system, provided it includes no bending elements, by an equivalent electric circuit. The author has been unable to discover any full description of the process, and the object of the present paper is to set out the principles underlying the procedure and to illustrate them briefly by examples.