Chalcogenide glasses of the Ge-Ga-S system were prepared using high purity (5 N) Ge, Ga and S. Molar volume, V, and glass transition temperature, T_g, were obtained from the measured densities and the differential scanning calorimetry (DSC) thermograms. The property-composition dependence is examined in the light of the chemically ordered covalent network (COCN) model and the topological models which are proposed for the atomic arrangement in these covalently bonded glasses.