Brillouin scattering from two classic glass‐forming materials, ZnCl2and glycerol, reveals a maximum in the ratio (&ggr;) of specific heatsCpandCvas a function of temperature. We propose that the temperature at which the maximum in &ggr; occurs in our materials may be indicative of a ‘‘liquid‐like’’ to ‘‘solid‐like’’ transformation. As such it may be a convenient thermodynamic signature of a ‘glass’ transition.