We have made sound-velocity measurements in the liquid crystal $p$-methoxy-benzylidine, $p-n$-butyl-aniline. Near the nematic-isotropic phase transition we observe a dispersion in the sound velocity. Quantitative measurements are presented on the sound-velocity anisotropy in an oriented liquid crystal.

• Received 15 February 1972

DOI:https://doi.org/10.1103/PhysRevLett.28.799