That iron could be melted and cast in moulds like other metals appears to have been known to the ancient Greeks, and it is not improbable that other nations of antiquity also became from time to time aware of the property; especially if it is the fact that primitive furnaces were sometimes constructed on exposed hillsides where the winds of heaven performed the function of bellows. Philosophers in all ages must have suspected, if indeed they did not absolutely know, that iron obeyed the universal law, melting as other metals do, but under a more intense heat. The absence of iron-casting in medieval times may be ascribed to the primitive hearths in general use, which were incapable of heating the ore to the melting point, while, no real demand existing, the iron-masters were never stimulated to furnish a supply.