Source : Webster's Revised Unabridged Dictionary (1913)

Evanesce \Ev`a*nesce"\, v. i. [imp. & p. p. {Evanesced}; p. pr.
   & vb. n. {Evanescing}. .] [L. evanescere; e out + vanescere
   to vanish, fr. vanus empty, vain. See {Vain}, and cf.
   {Evanish}.]
   To vanish away; to become dissipated and disappear, like
   vapor.

         I believe him to have evanesced or evaporated. --De
                                                  Quincey.