Scope and limitations of this book I am trying here to present the natural history of a land largely created and dominated by two great rivers, the Euphrates and Tigris. All rivers have two main functions, quite different from lakes; they transport water and eroded material sometimes over large distances. The astute Greeks, who penetrated here in the 4th century B.C., called the land Mesopotamia, an apt name; it is the only region in the Near East, except Egypt, having the benefit of large rivers. Another name coined in antiquity was 'Fertile Crescent', stretching from Egypt to present day Iraq; Herodotus marvelled at the fertility of the soils, the abundance of water and the magnificent cities of Mesopotamia. Thus a further role of some great rivers is recognized as foci of human development. The desire to collate this book arose from a similar motif as in the Nile book (1976), the intricate connection between man and rivers.