This article provides findings as of 1936. In general, the structural peculiarities of ancient bronze and copper are all readily attributable to the crude methods of smelting and treating the metals in the early days of civilization. There are some ancient metal objects that are almost free from the usual impurities and their structure is normal in every respect. There is no sign of change in or disintegration of the solid solutions or other components of the metal, except that due to corrosion; this applies even to specimens 5000 or 6000 years old. Microstructural features of initial corrosion and of patina rather than structure of metal give the most reliable proof of the ancient origin of the metal. Investigations disclosed characteristic differences in the initial corrosion of the many specimens of widely different origin or location examined. According to variations in the selective action and in the path of corrosion, six typical cases or distinct types of corrosion of copper and bronze were revealed.