The determination of the critical axial load of a strut having one or more intermediate supports and varying stiffness is made difficult by the highly transcendental nature of the simultaneous equations involved. It is therefore usual to make a test of the stability of the strut at some arbitrarily chosen load, as for example when applying the convergence technique. The behaviour of the strut then indicates whether the chosen load is too high or too low, and another load is selected and another test made. Although the true critical load is eventually reached, it is clear that if its value can be fairly closely approximated at the outset, then the labour of calculation will be greatly reduced.