HYDROMECHANICS HYTHE HYDROMEDUSAE I HYDROMETER IAMBIC HYDROPATHY IAMBLICHUS (Greek philosopher) HYDROPHOBIA IAMBLICHUS (Greek romance writer) HYDROSPHERE IANNINA HYDROSTATICS IAPETUS HYDROXYLAMINE IAPYDES HYDROZOA IATROCHEMISTRY HYENA IAZYGES HYÈRES IBADAN HYGIEIA IBAGUÉ HYGIENE IBARRA HYGINUS (eighth pope) IBERIANS HYGINUS (Latin writer) IBEX HYGINUS, GAIUS JULIUS IBIS HYGROMETER IBLIS HYKSOS IBN 'ABD RABBIHI HYLAS IBN 'ARABI HYLOZOISM IBN ATHIR HYMEN IBN BATUTA HYMENOPTERA IBN DURAID HYMETTUS IBN FARADI HYMNS IBN FARID HYPAETHROS IBN GABIROL HYPALLAGE IBN HAUKAL HYPATIA IBN HAZM HYPERBATON IBN HISHAM HYPERBOLA IBN ISHAQ HYPERBOLE IBN JUBAIR HYPERBOREANS IBN KHALDUN HYPEREIDES IBN KHALLIKAN HYPERION IBN QUTAIBA HYPERSTHENE IBN SA'D HYPERTROPHY IBN TIBBON HYPNOTISM IBN TUFAIL HYPOCAUST IBN USAIBI'A HYPOCHONDRIASIS IBO HYPOCRISY IBRAHIM AL-MAUSILI HYPOSTASIS IBRAHIM PASHA HYPOSTYLE IBSEN, HENRIK HYPOSULPHITE OF SODA IBYCUS HYPOTHEC ICA HYPOTHESIS ICE HYPOTRACHELIUM ICEBERG HYPSOMETER ICELAND HYRACOIDEA ICELAND MOSS HYRCANIA ICE-PLANT HYRCANUS ICE-YACHTING HYSSOP I-CH'ANG HYSTASPES ICHNEUMON HYSTERESIS ICHNEUMON-FLY HYSTERIA ICHNOGRAPHY HYSTERON-PROTERON HYDROMECHANICS ([Greek: hydromêchanika]), the science of the mechanics of water and fluids in general, including _hydrostatics_ or the mathematical theory of fluids in equilibrium, and _hydromechanics_, the theory of fluids in motion. The practical application of hydromechanics forms the province of hydraulics (q.v.). _Historical._--The fundamental principles of hydrostatics were first given by Archimedes in his work [Greek: Peri tôn ochoumenôn], or _De iis quae vehuntur in humido_, about 250 B.C., and were afterwards applied to experiments by Marino Ghetaldi (1566-1627) in his _Promotus Archimedes_ (1603). Archimedes maintained that each particle of a fluid mass, when in equilibrium, is equally pressed in every direction; and he inquired into the conditions according to which a solid body floating in a fluid should assume and preserve a position of equilibrium.