We shall now desist from comparisons and consider the formative age of Mesopotamia, which is called the Protoliterate period since it witnessed the invention of writing. To this period the earliest ruins of cities belong. Now one may say that the birth of Mesopotamian civilization, like its subsequent growth, occurred under the sign of the city. To understand the importance of the city as a factor in the shaping of society, one must not think of it as a mere conglomeration of people. Most modern cities have lost the peculiar characteristic of individuality which we can observe in cities of Renaissance Italy, of Medieval Europe, of Greece, and of Mesopotamia. In these counties the physical existence of the city is but an outward sign of close communal affinities which dominate the life of every dweller within the walls. The city sets its citizens apart from the other inhabitants of the land. It determines their relations with the outside world. It produces an intensified self-consciousness in its burghers, to whom the collective achievements are a source of pride. The communal life of prehistoric times became civic life. The change, however, was not without its disadvantages, especially in a country like Mesopotamia. The modest life of the prehistoric villager had fitted well enough into the natural surroundings, but the city was a questionable institution, at variance, rather than in keeping, with the natural order. This fact was brought home by the frequent floods and storms, droughts and marsh-fires with which the gods destroyed man’s work. For in Mesopotamia, in contrast with Egypt, natural conditions did not favour the development of civilization. Sudden changes could bring about conditions beyond man’s control.[88] Spring tides in the Persian Gulf may rise to a height of eight to nine feet; prolonged southerly gales may bank up the rivers for as much as two feet or more. Abnormal snowfalls in Armenia, or abnormal rainfall farther to the south, may cause a sudden rise of level in the rivers; a landslide in the narrow gorges of the two Zabs or of the Khabur may first hold up, then suddenly release, an immense volume of water. Any one of these circumstances, or the simultaneous occurrence of two or more of them, may create a flow which the earth embankments in the southern plain are not able to contain. In prehistoric times when primitive farmers sowed a catch crop after the inundation, it was possible to adapt human settlement to the ever-changing distribution of land and water, even though the villages were frequently destroyed. But large permanent towns, dependent upon drainage and irrigation, require unchanging watercourses. This can be achieved only through relentless vigilance and toil; for the quickly running Tigris carries so coarse a silt that canals easily get blocked. Even when cleaned annually, they rise gradually above the plain as a result of precipitation; and the risk that they, or the rivers