The Collaborative International Dictionary of English v.0.48:

Frictional \Fric"tion*al\, a.
   Relating to friction; moved by friction; produced by
   friction; as, frictional electricity.
   [1913 Webster]

   Frictional gearing, wheels which transmit motion by surface
      friction instead of teeth. The faces are sometimes made
      more or less V-shaped to increase or decrease friction, as
      required.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gearing \Gear"ing\, n.
   1. Harness.
      [1913 Webster]

   2. (Mach.) The parts by which motion imparted to one portion
      of an engine or machine is transmitted to another,
      considered collectively; as, the valve gearing of a
      locomotive engine; belt gearing; esp., a train of wheels
      for transmitting and varying motion in machinery.
      [1913 Webster]

   Frictional gearing. See under Frictional.

   Gearing chain, an endless chain transmitting motion from
      one sprocket wheel to another. See Illust. of Chain
      wheel.

   Spur gearing, gearing in which the teeth or cogs are ranged
      round either the concave or the convex surface (properly
      the latter) of a cylindrical wheel; -- for transmitting
      motion between parallel shafts, etc.
      [1913 Webster]