d="p-1">Investigating waves for sedimentary series, Morlet et al. start from basic formulas for elastic waves. I have compared formulas used by Morlet et al. for: (a) compressional velocity of elastic waves, (b) stress-strain relationship, and (c) energy flow vector (Poynting's vector), with corresponding formulas in Koehler and Taner (1977). The results follow.