From Earth's two longest rivers, which flow through African deserts and Amazon jungles, to Siberia's great Yenisei-Angara river system, which drains into the Arctic Ocean, this appealing new book vividly brings the world's great waterways into focus. Students will discover how these rivers came to exist, their place in history, what makes each unusual, and current environmental challenges. ''In the Field'' sidebars cover such topics as monitoring salinity, measuring flow, drilling for oil, ice breakers in action, and more. Photographs, line illustrations, a scientific glossary, and resource listings for further information handsomely supplement the text.