In Egypt it was the banks and delta of the Nile which took the place of the Babylonian plain. Recent discoveries have shown that in the prehistoric age, when the natives still lived in the desert and led a pastoral life, all this was a morass, the haunt of beasts of prey and venomous reptiles. But here again the swamp was rendered habitable by engineering works similar to those of primeval Babylonia. The swamp was transformed into fertile fields, the annual flood of the river was regulated, and an elaborate network of canals and embankments spread over the country. The pastoral nomads of the neolithic age became agriculturists, or were employed in constructing and repairing the works of irrigation, or in erecting monumental buildings for their rulers. There is evidence of the same centralized government, the same directing brain and organizing force that there is in primitive Babylonia. Is it possible that two systems of engineering science, so similar in their objects, their methods and their results, should have been invented independently in two different countries? There are scholars who answer in the negative. But the possibility cannot be denied, since an even more elaborate system of irrigation was invented in China without any suggestion, as far as we know, from outside. The geographical conditions of Babylonia and Egypt, moreover, resemble one another, and the question of draining the swamps and regulating the overflow of the rivers once raised, the answer to it seems fairly obvious. By itself, therefore, the fact that the cultures of ancient Babylonia and Egypt alike rested on a similar system of irrigation engineering would be no proof of their common origin. In some respects the problem which the Babylonian engineers were called upon to solve was more difficult than that which faced the Egyptians. The Nile is fed by the rains and melting snows of Abyssinia and Central Africa, and its annual inundation takes place in the later summer months. The Euphrates and Tigris flow from the north, from the highlands of Armenia, and are at their fullest in the spring. Their overflow accordingly comes just before the summer heats, when agriculture is difficult or impossible, whereas in Egypt the period of inundation ushers in the most favourable time of the year for the growth of the crops. What the Babylonian engineers had to do was not only to drain off the overflow, but also to store it for use at least six months later. With them it was a question of storage as well as of regulation.