The Collaborative International Dictionary of English v.0.48:

Gradualness \Grad"u*al*ness\, n.
   The quality or state of being gradual; regular progression or
   gradation; slowness.
   [1913 Webster]

         The gradualness of this movement.        --M. Arnold.
   [1913 Webster]

         The gradualness of growth is a characteristic which
         strikes the simplest observer.           --H. Drummond.
   [1913 Webster]

WordNet (r) 3.0 (2006):

gradualness
    n 1: the property possessed by a slope that is very gradual
         [syn: gradualness, gentleness] [ant: abruptness,
         precipitousness, steepness]
    2: the quality of being gradual or of coming about by gradual
       stages [syn: graduality, gradualness]