The method of wave splitting is a powerful technique for solving one- dimensional time-dependent direct and inverse problems. The author considers the wave equation for a stratified medium where the stratifications are in the form of a family of nested \(C^ 2\) surfaces along which the velocity c is constant and, using potential type integral operators (single and double layer potential type) he gives the expression of incoming and outgoing wave conditions for surfaces where c is constant. Then the scalar wave equation is split into a vector system involving the components u \(+\) (outgoing wave) and u - (incoming wave). As pointed out in the paper this system is decoupled in a region where c is constant.