\Link" mo"tion\ (m[=o]"sh[u^]n). (Steam Engine)
A valve gear, consisting of two eccentrics with their rods,
giving motion to a slide valve by an adjustable connecting
bar, called the link, in such a way that the motion of the
engine can be reversed, or the cut-off varied, at will; --
used very generally in locomotives and marine engines.
Note: The illustration shows a link motion for a vertical
      engine, c representing the shaft carrying two
      eccentrics, a and b, for making the engine run forward
      and backward, respectively, their rods e and d being
      jointed to opposite ends of the slotted link f, in the
      opening of which is a pin g which is attached to the
      valve rod h. The valve will receive the motion of the
      forward eccentric when the link is in the position
      shown, and the motion of the backward eccentric when
      the link is shifted so far to the right as to bring e
      in line with h, or a compound motion derived from both
      eccentrics when the link is shifted to intermediate
      positions, the compound motion causing the valve to cut
      off the steam at a point determined by the position to
      which the link may have been shifted.