What is "dactylology"

Dactylology \Dac`tyl*ol"o*gy\, n. [Gr. da`ktylos finger + -logy.] The art of communicating ideas by certain movements and positions of the fingers; -- a method of conversing practiced by the deaf and dumb.

Note: There are two different manual alphabets, the one-hand alphabet (which was perfected by Abb['e] de l'Ep['e]e, 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.

n. The use of the fingers and hands to communicate ideas, especially by the deaf.