History 21
Description and travel 15
Stream measurements 6
Water-supply 4
Civilization 3
Irrigation 3
Geology 2
Politics and government 2
Prehistoric peoples 2
Agriculture 1
Analysis 1
Antiquities 1
Arabic literature 1
Art, Egyptian 1
Canoes and canoeing 1
Discovery and exploration 1
Explorers 1
Geography 1
History and criticism 1
History, Naval 1
In literature 1
Landscape changes 1
Navigation 1
Piracy 1
Regulation 1
Relations 1
Religion 1
Religious aspects 1
Rivers 1
Sea-power 1
Silt 1
Social life and customs 1
Soils 1
Surveys 1
Water 1
Water resources development 1
Water use 1
Waterways 1