A hegemony is leadership or dominance, especially that of one state or nation over others. In Ulysses, the author describes what Leopold Bloom admires about water:
Its universality: its democratic equality and constancy to its nature in seeking its own level: . . . its climatic and commercial significance: its preponderance of 3 to 1 over the dry land of the globe: its indisputable hegemony extending in square leagues over all the region below the subequatorial tropic of Capricorn.