The chief work of Egyptian civilization was the proper irrigation of the alluvial soil, the turning of marsh into cultivated fields, and the reclamation of land from the desert for the purposes of agriculture. Owing to the rainless character of the country, the only means of obtaining water for the crops is by irrigation, and where the fertilizing Nile water cannot be taken by means of canals, there cultivation ends and the desert begins. Before Egyptian civilization, properly so called, began, the valley was a great marsh through which the Nile found its way north to the sea. The half-savage, stone-using ancestors of the civilized Egyptians hunted wild fowl, crocodiles, and hippopotami in the marshy valley; but except in a few isolated settlements on convenient mounds here and there (the forerunners of the later villages), they did not live there. Their settlements were on the dry desert margin, and it was here, upon low tongues of desert hill jutting out into the plain, that they buried their dead. Their simple shallow graves were safe from the flood, and, but for the depredations of jackals and hyenas, here they have remained intact till our own day, and have yielded up to us the facts from which we have derived our knowledge of prehistoric Egypt. Thus it is that we know so much of the Egyptians of the Stone Age, while of their contemporaries in Mesopotamia we know nothing, nor is anything further likely to be discovered. But these desert cemeteries, with their crowds of oval shallow graves, covered by only a few inches of surface soil, in which the Neolithic Egyptians lie crouched up with their flint implements and polished pottery beside them, are but monuments of the later age of prehistoric Egypt. Long before the Neolithic Egyptian hunted his game in the marshes, and here and there essayed the work of reclamation for the purposes of an incipient agriculture, a far older race inhabited the valley of the Nile. The written records of Egyptian civilization go back four thousand years before Christ, or earlier, and the Neolithic Age of Egypt must go back to a period several thousand years before that. But we can now go back much further still, to the Palaeolithic Age of Egypt. At a time when Europe was still covered by the ice and snows of the Glacial Period, and man fought as an equal, hardly yet as a superior, with cave-bear and mammoth, the Palaeolithic Egyptians lived on the banks of the Nile. Their habitat was doubtless the desert slopes, often, too, the plateaus themselves; but that they lived entirely upon the plateaus, high up above the Nile marsh, is improbable. There, it is true, we find their flint implements, the great pear-shaped weapons of the types of Chelles, St. Acheul, and Le Moustier, types well known to all who are acquainted with the flint implements of the “Drift” in Europe. And it is there that the theory, generally accepted hitherto, has placed the habitat of the makers and users of these implements.