58 Outlines of European History of the agricultural peasant. This slow shift at times swells into a great tidal wave of migration, when the wild hordes of the wilderness roll in upon the fertile shores of the desert-bay — a human tide from the desert to the towns which they overwhelm. We can see this process going on for thousands of years. Among such movements we are familiar with the passage of the Hebrews from the desert into Palestine, as described in the Fig, 36. The Euphrates at Babylon in Winter The winter rainfall (p. 61) is so slight that the river shrinks to a very low level and its bed is exposed and dry almost to the middle. In summer the rains and melting snows in the northern mountains swell the river till it overflows its banks and inundates the Babylonian plain. The house on the right is the dwelling of the German Expedition still engaged in excavating Babylon Bible ; and we shall later learn (Chapter XIV) of the invasions of the Arab hosts of Islam, which even reached Europe. After they had adopted a settled town life the colonies of the Semites stretched far westward through the Mediterranean, especially in northern Africa, even to southern Spain and the Atlantic (see diagram, Fig. 49). But it took many centuries for the long line of their settlements to creep slowly westward until it reached the Atlantic, and we must begin with the Semites in the desert.
