An elegant symbolic method of solving differential equations was developed by Heaviside in his “Electrical Papers” and “Electromagnetic Theory,” chiefly in connexion with problems concerning electric currents in net-works of wires. Attention has recently been called to the method by Bromwich, who applied it to a wider range of problems and gave an extension of Heaviside's formula; another generalisation of the formula has been obtained by Carson.

In the present paper a formula is obtained which contains the formulae of Heaviside, Bromwich and Carson as particular cases, and whose form is such that it may be readily applied to physical problems.