The Collaborative International Dictionary of English v.0.48:

Rabdology \Rab*dol"o*gy\ (r[a^]b*d[o^]l"[-o]*j[y^]), n. [Gr.
   "ra`bdos rod, stick + -logy: cf. F. rabdologie.]
   The method or art of performing arithmetical operations by
   means of Napier's bones. See Napier's bones. [Written also
   rhabdology.]
   [1913 Webster]