Given an electric network Ev which has M meshes and P node‐pairs, its electric dual Ei will have P meshes and M node‐pairs and its classical mechanical analog Mf will have M+1 nodes, M independent node‐pairs, and P independent node cycles. A second mechanical system Mv, the classical analog of Ei, will have M cycles and P node‐pairs. If, for example, M = 2, P = 3, the systems Ev and Mv, analogs in the Firestone or “mobility” method, will be governed by two mesh equations, expressing that the algebraic sum of the voltages or velocities around any loop is zero; the systems Ei and Mf, also Firestone analogs, will satisfy two node equations, expressing that the algebraic sum of the currents or forces leaving any node is zero. These four sets of equations are identical, interchanging symbols suitably. The consideration of the four systems, Ev, Ei, Mv, Mf, forming a complete set, shows the advantages of the Firestone over the classical system of analogies and suggests a systematic use of duality in mechanical as well as in electrical systems.