"I thought how lovely and how strange a river is. A river is a river, always there, and yet the water flowing through it is never the same water and is never still. It's always changing and is always on the move. And over time the river itself changes too. It widens and deepens as it rubs and scours, gnaws and kneads, eats and bores its way through the land. Even the greatest rivers- the Nile and the Ganges, the Yangtze and he Mississippi, the Amazon and the great grey-green greasy Limpopo all set about with fever trees-must have been no more than trickles and flickering streams before they grew into mighty rivers.