\Hy*drau"lic\, a. [F. hydraulique, L. hydraulicus, fr.
Gr. ?, ?, a water organ; "y`dwr water + ? flute, pipe. See
{Hydra}.]
Of or pertaining to hydraulics, or to fluids in motion;
conveying, or acting by, water; as, an hydraulic clock,
crane, or dock.
{Hydraulic accumulator}, an accumulator for hydraulic
   machinery of any kind. See {Accumulator}, 2.
{Hydraulic brake}, a cataract. See {Cataract}, 3.
{Hydraulic cement}, a cement or mortar made of hydraulic
   lime, which will harden under water.
{Hydraulic elevator}, a lift operated by the weight or
   pressure of water.
{Hydraulic jack}. See under {Jack}.
{Hydraulic lime}, quicklime obtained from hydraulic
   limestone, and used for cementing under water, etc.
{Hydraulic limestone}, a limestone which contains some clay,
   and which yields a quicklime that will set, or form a
   firm, strong mass, under water.
{Hydraulic main} (Gas Works), a horizontal pipe containing
   water at the bottom into which the ends of the pipes from
   the retorts dip, for passing the gas through water in
   order to remove ammonia.
{Hydraulic mining}, a system of mining in which the force of
   a jet of water is used to wash down a bank of gold-bearing
   gravel or earth. [Pacific Coast]
{Hydraulic press}, a hydrostatic press. See under
   {Hydrostatic}.
{Hydraulic propeller}, a device for propelling ships by means
   of a stream of water ejected under water rearward from the
   ship.
{Hydraulic ram}, a machine for raising water by means of the
   energy of the moving water of which a portion is to be
   raised. When the rush of water through the main pipe d
   shuts the valve at a, the momentum of the current thus
   suddenly checked forces part of it into the air chamber b,
   and up the pipe c, its return being prevented by a valve
   at the entrance to the air chamber, while the dropping of
   the valve a by its own weight allows another rush through
   the main pipe, and so on alternately.
{Hydraulic valve}. (Mach.)
(a) A valve for regulating the distribution of water in the
    cylinders of hydraulic elevators, cranes, etc.
(b) (Gas Works) An inverted cup with a partition dipping into
    water, for opening or closing communication between two
    gas mains, the open ends of which protrude about the
    water.