1911 Encyclopædia Britannica/Hydrosphere

HYDROSPHERE (Gr. ὕδωρ, water, and σφαῖρα, sphere), in physical geography, a name given to the whole mass of the water of the oceans, which fills the depressions in the earth’s crust, and covers nearly three-quarters of its surface. The name is used in distinction from the atmosphere, the earth’s envelope of air, the lithosphere (Gr. λίθος, rock) or solid crust of the earth, and the centrosphere or interior mass within the crust. To these “spheres” some writers add, by figurative usage, the terms “biosphere,” or life-sphere, to cover all living things, both animals and plants, and “psychosphere,” or mind-sphere, covering all the products of human intelligence.