* That part of mechanics which considers the action of forces in producing rest or equilibrium is called statics; that which relates to such action in producing motion is called dynamics. The term mechanics includes the action of forces on all bodies, whether solid, liquid, or gaseous. It is sometimes, however, and formerly was often, used distinctively of solid bodies only: The mechanics of liquid bodies is called also hydrostatics, or hydrodynamics, according as the laws of rest or of motion are considered. The mechanics of gaseous bodies is called also pneumatics. The mechanics of fluids in motion, with special reference to the methods of obtaining from them useful results, constitutes hydraulics.

Animal mechanics (Physiol.), that portion of physiology which has for its object the investigation of the laws of equilibrium and motion in the animal body. The most important mechanical principle is that of the lever, the bones forming the arms of the levers, the contractile muscles the power, the joints the fulcra or points of support, while the weight of the body or of the individual limbs constitutes the weight or resistance. -- Applied mechanics, the principles of abstract mechanics applied to human art; also, the practical application of the laws of matter and motion to the construction of machines and structures of all kinds.