But now comes a fact which is difficult to explain, so contrary is it to the archæological evidence. As we have seen, no traces of bronze have been found in the Assyro-Babylonian region before the beginning of the Assyrian age--let us say about B.C. 2000. Nevertheless, by the side of the simple ideograph which denotes the Sumerian _urudu_, “copper”--_erû_ in Semitic Babylonian--we find a compound ideograph signifying “bronze,” called _zabar_ in Sumerian, from which the Semites borrowed their _’siparru_. It is true that it is a compound ideograph, but it occurs in the cuneiform texts, not only in the era of Gudea (B.C. 2700), but even before the age of Sargon of Akkad (B.C. 3800). And an analysis of its earliest form seems to indicate that it really must have meant bronze from the first, and that consequently there was no transference of signification in later days. Literally it means “white copper,” the word for “copper” being phonetically-written _ka-mas_, with which the Semitic Babylonian _kemassu_ is closely connected. Lead cannot be intended, as that was denoted by a different word and different ideographs, and I do not see what else “white copper” can be in contradistinction to red copper except bronze. Polished copper could be termed “bright,” but hardly “white.”[59] The possibility remains that tin might have been the metal originally denoted by the compound ideograph. If so, both the ideograph and the words expressed by it had lost all reference to tin before the beginning of the Assyrian period, and neither the Assyrian word for “tin” nor the Sumerian word, if any existed, is now known. Tin, moreover, was archæologically late in making its appearance. The earliest examples of pure tin of which I know are of the time of the Eighteenth Egyptian dynasty. On the other hand, bronze first appears in Egypt in the age of the Twelfth dynasty,[60] though it does not become common until the Hyksos predecessors of the Eighteenth dynasty had made themselves masters of the valley of the Nile. From about B.C. 1600 onwards, enormous quantities of it were employed in the eastern basin of the Mediterranean and the adjoining lands, necessitating an equally large supply of tin. What the source of this tin may have been it is not my present purpose to inquire. But the persistence of the copper age in Babylonia, as well as in the tumuli of Askabad, east of the Caspian, indicates that the manufacture of bronze must have migrated from the north-west to the Babylonian plain. We find it first in Assyria, not in Babylonia, and it may well be that the Assyrians derived it from Armenia and the population of Cappadocia, where, as I shall show in a subsequent chapter, they had established colonies at an early period. At all events, the earliest examples of bronze yet met with were discovered by Dr. Schliemann in the Second prehistoric city at Troy.