The first two chapters outline the causes of circulation patterns in the atmosphere and oceans, emphasizing the interactions between them. Chapter 3 deals with the surface circulation (including mesoscale eddies), using a minimum of mathematics. Chapter 4 reviews the history of ideas about ocean circulation (with special reference to the North Atlantic gyre), and Chapter 5 describes the major current systems at high and low latitudes. The final Chapter returns to the theme of ocean-atmosphere interaction, especially the global transport of heat and freshwater, and the formation of sub-surface water masses.