Ber·noul·li \bər-ˈnü-lē, ber-ˈnü-ē, ˌber-ˈnü-ˌ(y)ē\ , Daniel (1700–1782), Swiss mathematician and physicist. Bernoulli came from an illustrious family that produced eight outstanding mathematicians in three generations. In 1724 he demonstrated his own mathematical ability by producing a treatise on differential equations and the physics of flowing water. In 1738 he published his great work, Hydrodynamica. The work examined the basic properties of fluid flow, particularly density, pressure, and velocity. Bernoulli stated the fundamental relationships between these properties, set forth the principle now known as Bernoulli's principle, and established the basis for the kinetic theory of gases and heat. A scientist of catholic interests, he did research on such diverse subjects as astronomy, the properties of vibrating and rotating bodies, gravity, magnetism, tides and ocean currents, and probability theory.