The solution of some non-self-adjoint eigensystems describing the elastic instability of structural elements requires essentially the determination of the minimum value of a parameter associated with the eigenvalues. Usually, a substantial programme of computation is implicit in this type of system.

During a preliminary consideration of possible methods of practical computation for a certain problem of this kind, which is currently being investigated by the author, the question arose concerning the suitability of a finite-difference approximation for the purpose. The object of such an approximation was to provide a relatively rapid, if crude, means for a first estimate of the solution by desk-calculation methods.