sentences:  It is likely that Watson's second patent, "Improvements in Flying Machines" dated 1 January 1909 was the first published description of Watson's rocking wing theory of lateral control, the function of which in a practicable sense is described by him as, "above [the main] plane...and carried by the frame of the machine is a rocking aeroplane...capable of rocking about a fore and aft central axle..."
  
  "The pivot...is above the fore and aft central axis of the main plane and depending from the rocking plane and at right angles to it is a lever...fixed rigidly to such rocking plane.This lever is fixed in so far that it can tilt the plane...to one side or the other..." The actuation of which by the pilot induces the rocking motion of the wing.When in flight the rocking wing functions in the following manner, "when the rocking aeroplane...is tilted out of the horizontal...by moving the lever...to one side, the normal pressure of the rocking aeroplane...is inclined out of the vertical and gives rise to a horizontal component pulling its axle...to one side relative to the line of flight."