In Part III of this paper the formulae deduced in the previous parts are applied to the case of heating glass under constant gradient and the temperature at which strain disappears is obtained, the effect of the known change in the coefficient of expansion on this temperature being discussed. The calculated and experimental curves are compared and the effect of changes in the rate of heating and in the size of the specimens is considered. In Part IV the annealing equation is considered from the point of view of dimensions. The agreement of theory and experiment is discussed and an explanation of the discrepancies at low temperatures is advanced. A general expression to cover all cases is deduced and the results of theory and experiment are compared.