The Collaborative International Dictionary of English v.0.48:

-ance \-ance\ [F. -ance, fr. L. -antia and also fr. -entia.]
   A suffix signifying action; also, quality or state; as,
   assistance, resistance, appearance, elegance. See -ancy.
   [1913 Webster]

   Note: All recently adopted words of this class take either
         -ance or -ence, according to the Latin spelling.
         [1913 Webster]