Egypt, wrote the Greek historian Herodotus, is the gift of the Nile. He was right; Egyptor at least its most populous and fertile areawas formed by the rich silt washed down from the East African highlands by the waters of the Nile. But which Nile? According to Egypt's leading geologist, Rushdi Said, 55, the present-day Nile is a relative newcomer to Egypt, having been around for only 30,000 years. Before that, he says, at least four different Niles had flowed throughand then disappeared fromthe river basin.
Said, who heads the Geological Survey of Egypt and holds a seat in the Egyptian Parliament,...