dactylology \dac`tylol"ogy\, n. gr. da`ktylos finger +
   -logy.
   the art of communicating ideas by certain movements and
   positions of the fingers; a form of sign language, especially
   the manual alphabets used by the deaf and dumb.
   1913 webster +pjc

   note: there are two different manual alphabets, the one-hand
         alphabet which was perfected by abb'e de l'ep'ee,
         who died in 1789, and the two-hand alphabet. the
         latter was probably based on the manual alphabet
         published by george dalgarus of aberdeen, in 1680. see
         illustration in appendix.
         1913 webster