IN egypt, 6000 years ago, when the latest rainy interlude began to wane, neo? lithic tribesmen from both sides flocked into the Nile Valley and there perforce exchanged pastoral existence for an agricultural one. The nomads who remained in the eastern desert could do little more than follow the scanty rains; west of the Nile, where there is no wadi network to concentrate the fall, the rain evaporated as it fell, the water table sank out of reach and the victory of nature over nomadic man was complete. Within few generations the peasant Egyptian had become, in Winkler's phrase, a stranger to the desert, the land of his forefathers. Some centuries later, when the kingdoms of Upper and Lower Egypt had united, the coordination of labour into vast gangs had strengthened man's hand, and now and again he began to fight back. To the deserts the new strangers returned to seek gold and copper, turquoise and ornamental stone; and, to sustain their assaults, water was necessary. The Bedouin cousins of the Egyptians had done no more than scoop out few shallow holes. Now, some unknown Pharaoh, with an architect far ahead of his time, attacked the problem in the grand style of the Pyramid Age. The oldest dam in the world.?Seven miles south-east of Helwan, in the Wadi el-Garawi, one may still see the abutments of the Sadd el-Kafara, the Dam of the Pagans, the first of its kind in history and one whose failure was so catastrophic that nothing of the sort was attempted again till over 3000 years had passed.1 Its age is not in dispute. From the style of its masonry and the nature of the potsherds lying in the workmen's huts about 200 yards from the site, Professor Schweinfurth who discovered the dam in 1885,2 Mr. Ernest Mackay who visited it in 1915 3 and Mr. Guy Brunton who accompanied me to the site in 1935,4 all agreed in ascribing its erection to the period of the Illrd or IVth Dynasties, from 2950 to 2750 B.C. For an initial experiment in dam construction, the size of the structure is surprising: I took the measurements quoted myself in June 1945. It is 348 feet long at the top and about 265 feet at the base; the lintel stood 37 feet above the lowest point in the wadi floor; and, passing through the great breach, one sees that the dam was composite. That is, it was made up of two separate rubble masonry dams, each 78 feet thick at the base, with space of 120 feet at ground level between them, which was later filled in with over 60,000 tons of shingle from the wadi bed and rubble from the hillsides. Beyond that, some 30,000 cubic yards of rubble masonry, say 40,000 tons, were employed in the construction of the upstream and downstream dams?a task that must have occupied the energies of many hundreds of men and animals for whole season in this desert place, 9 miles from the Nile cultivation.