Source : Webster's Revised Unabridged Dictionary (1913)

Graveness \Grave"ness\, n.
   The quality of being grave.

         His sables and his weeds, Importing health and
         graveness.                               --Shak.

Source : WordNet®

graveness
     n : a manner that is serious and solemn [syn: {gravity}, {sobriety},
          {soberness}, {somberness}]