Book excerpt: From Herodotus's day to the present political upheavals, the steady flow of the Nile has been Egypt's heartbeat. It has shaped its geography, controlled its economy and moulded its civilisation. The same stretch of water which conveyed Pharaonic battleships, Ptolemaic grain ships, Roman troop-carriers and Victorian steamers today carries modern-day tourists past bankside settlements in which rural life – fishing, farming, flooding – continues much as it has for millennia. At this most critical juncture in the country's history, foremost Egyptologist Toby Wilkinson takes us on a journey up the Nile, north from Lake Victoria, from Cataract to Cataract, past the Aswan Dam, to the delta. The country is a palimpsest, every age has left its trace: as we pass the Nilometer on the island of Elephantine which since the days of the Pharaohs has measured the height of Nile floodwaters to predict the following season's agricultural yield and set the parameters for the entire Egyptian economy, the wonders of Giza which bear the scars of assault by nineteenth-century archaeologists and the modern-day unbridled urban expansion of Cairo – and in Egypt's earliest art (prehistoric images of fish-traps carved into cliffs) and the Arab Spring (fought on the bridges of Cairo) – the Nile is our guide to understanding the past and present of this unique, chaotic, vital, conservative yet rapidly changing land.